Historical vulnerability of manatees to boat strikes in Florida

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By Haley Kilgour, SRC MPS student

Manatees are an iconic species of Florida and for many years they have been one of the main focuses of conservation. Placed on the endangered species list in 1967, manatees have managed to make a comeback from their population containing only a few hundred individuals to over 6,000 (2016 count) (Gast, 2017). Now, as of March 31, 2017 Manatees have been “downlisted” to threatened (Gast, 2017). But that does not mean their troubles are over.

There are three major criteria for the downlisting of a species: 1) population must be growing or stable, 2) mortality factors must be decreasing or controlled at acceptable levels, and 3) habitats must be secure (Marsh and Lebefvre, 1994). As it stands, manatee populations have increased enough to meet the first criterion, but the second statue is not being met and the third criteria can be a hit or miss, depending on the location you are referring to. While still protected by the Marine Mammal Protection Act (1972) and the Endangered Species Act (1973) (Marsh and Lebefvre, 1994), hundreds of manatees are still killed by anthropogenic means. Roughly 30% of annual mortalities are from vessel collisions (Aipanjiguly, 2003 and Nowacek, 2004); of 520 deaths in 2016, 104 were from boats (Gast). Figure 1 demonstrates how many manatees are hit by boats. It is without a doubt that boat collisions are the number one reason for manatee deaths (Runge et al., 2007; Runge et al., 2016; Marsh and Lebefvre, 1994; Aipanjiguly, 2003; Baudin et al., 2012; Nowacek et al., 2004). While all manatee-boat collisions do not result in death, 97% of manatees bear scar patterns, which can be used to identify them (Nowacek et al., 2004). It must also be noted that mortality from collision can occur year round and involve all age classes (Nowacek et al., 2004).

Figure 1: Manatee deaths caused by boat collisions, focusing mostly on deaths within 5 kilometers of marinas. Deaths shown are from 1976 –present.

Manatees are classified as a marine species but they require access to deep water and freshwater, and thus can be found in inland rivers, coastal estuaries, seagrass beds, and marinas (Marmontel et al., 1997). Manatees feed exclusively on seagrass and these beds are found almost entirely in publically owned waters (Marmontel et al., 1997). Bauduin et al. (2013) found that manatees do no avoid developed areas, so it is humans that need to change their practices if this species is to persist.

Nowacek et al. (2004) found that the best way to reduce manatee morality from anthropogenic causes is to reduce boat speeds in areas of high density. Something to note is that manatee protection zones have been implemented since 1979 (Edwards et al., 2016), but not much has changed as far as mortality from boat collisions. Possible reasons for this is that regulations are either not being enforced or that further restrictions are necessary (Nowacek et al., 2004).  One excellent example of blatant disregard of regulation is seen in the Bear Cut protection zone where even police boats ignore the no wake zone.  In situations like this more stringent law enforcement and education is required to remedy the problem.

It is important to decrease boat speeds in areas of high manatee density because the manatees need time to respond. Nowacek et al. (2004) found that manatees do not respond to boats until the vessel is on average about 25-50 meters away. Another problem is that in areas of high boat traffic, manatees have problems distinguishing multiple inputs. Even with conservation efforts well underway, the number of carcasses recovered each year is close to 200 (Marsh and Lebefvre, 1994). It is necessary to decrease the number of deaths from boat strikes because Runge et al. (2012) found manatee populations are still capable of dropping below a critical threshold within 50-100 years if current mortality patterns persist.

Figure 2: A map of manatee vulnerability based upon deaths near marinas.

With only four extant species of Sirenia, it is important to persevere these charismatic creatures. While it may be an overreach to want to prevent all manatee deaths from boat collisions, it is plausible to decrease the number. Creating more speed-limit zones will give manatees adequate time to avoid boats, which is one or the largest reasons they are hit. And for those that choose to ignore regulations, they need to face larger consequences from a law agency that enforces what they are supposed to. Education can also be key in helping people understand the reasons behind restrictions and the necessity to abide by them, as well as to increase awareness of manatees while operating watercraft.

References

Aipanjiguly, Sampreethi, et al. “Conserving Manatees: Knowledge, Attitudes and Intentions of Boaters in Tampa Bay, Florida.” Conservation Biology, vol. 17, no. 4, 2003, pp. 1098-1105

Baudin, Sarah, et al. “An index of risk of co-Occurance between marine mammals and watercraft: Example of the Florida manatee.” Biological Conservation, vol. 159, 2013, pp. 127-136.

Edwards, H. H, et al. “Influence of manatees’ diving on their risk of collision with watercraft”. PLoS One, 11. 2016

Gast, Phil. “It’s Official: Manatee no longer endangered.” CNN, Cable News Network, 31 Mar. 2017.

Marsh, H., and Lebefvre, L. W. “Sirenian status and conservation efforts.” Aquatic Mammals, vol. 20, no. 30, 1994, pp. 155-170.

Marmontel, Miriam, et al. “Population Viability Analysis of the Florida Manatee (Trichechus manatus latirostris), 1976-1991. Conservation Biology, vol. 11, no. 2, 1997, pp. 467-481.

Nowacek, Stephanie M, et al. “Florida manatees, Trichechus manatus latirostris, respond to approaching vessels.” Biological Conservation, vol. 119, no. 4, 2004, pp. 517-523.

Runge, Michael C., et al. “Status and threats analysis for the Florida manatee (Trichechus manatus latirostris), 2012.” Open-File Report, 23 Mar. 2007.

Runge, M.C., et al. “Status and threats analysis for the Florida manatee (Trichechus manatus latirostris)”, 2016.

What’s in a name? How common and scientific names affect conservation efforts

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By Nicole Suren, SRC intern

Conservation efforts often focus on language to rally support for an ecological cause, and the names of what they are rallying support for are an integral part of that language. Both scientific and common names can have huge impacts on the success of conservation efforts, either by influencing the way the organisms are perceived by the public, or by being used to correctly or incorrectly identify a species to be conserved. Scientific names tend to be most important when examining the specificity of a name (i.e. how many names an organism has or whether a species has been named correctly), which can be integral in determining an organism’s conservation status. Common names are generally important in how the organism is perceived, affecting conservation in a completely different, and much more social way.

Scientific names, as one may intuitively be able to guess, are those most often used to identify individual species in scientific studies or by scientists, and always consist of two Latin names describing the genus and species. Because of their Latin roots, they are seldom used in common language and are rarely considered by non-scientists when thinking of the organism they describe. However, scientific names are very important in conservation because of their importance in correctly identifying and classifying organisms to determine how they should be managed, or whether they are recognized by policy makers as worthy of increased conservation measures. For example, the ICUN Red list, a comprehensive list of organisms that are facing the threat of extinction, is organized by scientific name (“ICUN Red List,” 2017), and this list is commonly used to determine which species or regions need to be more strictly managed. An example of a situation where the scientific name of a species was not used correctly was in the case of the European Common Skate. For decades, the European Common Skate was recognized as one species and considered critically endangered by the ICUN red list, but further studies revealed that it actually consisted of several species of skates that reached sexual maturity at significantly different sizes (Iglésias, Toulhoat, & Sellos, 2010). This misclassifying and misnaming of the species greatly affected the way the conservation needs of each type of skate were considered, and the discovery of the new species resulted in the need for a comprehensive reevaluation of conservation requirements for each species.

Dipturus flossada and Dipturus intermedia, the two skates previously thought to be a single species, along with other closely related species of skate (Iglésias, Toulhoat, & Sellos, 2010)

According to a culturomic study where presence of common and scientific names on the internet was used as a proxy for the presence of the named organisms in the general social consciousness, such a revision of scientific names can also reduce the cultural salience of an organism (Correia, Jepson, Malhado, & Ladle, 2017). This means that while the revision of the taxonomic status of a species can result in a heightened scientific awareness of the needs of that species, it can also result in a lowered social awareness, presenting a new conservation challenge even when progress in identifying needs has been made.

The words used to form common names are incredibly important in the way people perceive the organisms the names are describing. Generally speaking, common names can describe biological features, distribution, natural history, and/or phylogeny of the organism (Sarasa et al., 2012), and thus can be very informative on their own. However, particular words within a common name can greatly affect how much attention people believe the organism is worthy of receiving. For example, any organism with the word “rat” in its common name is less likely to receive positive human attention due to its common name being reminiscent of vermin, and the words “wild” or “feral” can also have negative connotations when the organisms are unfamiliar. So much so, that some conservationists are trying to change the common name of wild dogs to “painted hunting dogs” to avoid this negative perception (Sarasa et al., 2012). Another factor that can greatly affects the conservation goals of a species is how much its common name resembles that of a domesticated animal. According to the study by Sarasa et al., it seems that people tend to think animals with common names similar to domesticated animals deserve the treatment the domestic animals receive. This can be helpful in that people believe the animals should be conserved, but it can also be problematic because it also seems to make selective breeding programs in wild populations more acceptable. PETA seems to be using this principle in a recent marketing campaign it is calling “Save the Sea Kittens” (PETA, n.d.). The organizers of this campaign are pushing for fish to be renamed “sea kittens” under the premise that no one would hurt a kitten, and therefore they should be less likely to want to hurt a “sea kitten.” Whether this has been an effective ad campaign or has pushed this conservation naming principle beyond what is reasonable remains to be seen, but the idea remains the same: people want to protect their pets, and therefore would want to extend a similar protection to their pets’ close relatives.

Naming has been an especially effective marketing tool when it comes to fish, but it has been used to effectively oppose conservation rather than encourage it. Using the same principles of changing the common name of an organism to make it sound more appealing or likeable, companies that sell fish have been able to take species such as spiny dogfish and Patagonian toothfish and turn them into rock salmon and Chilean seabass, which are now recognized as bestsellers, and have been dangerously overfished (Logan et al., 2008). They have also been able to market groups of fish under one name. For example, “whitefish” can include halibut, Alaskan Pollock, sole, and cod. Including many fish under one name can also inhibit conservation efforts because it reduces consumer purchasing power in controlling options available on the market (Logan et al., 2008). When it is unclear what species are included in a package of “whitefish,” consumers no longer have the power to choose sustainably caught fish over endangered fish because they are sold without being able to discern between the two.

Alaskan Pollock, cod, or whitefish? Theragra chalcogramma goes by all three names (Wikimedia commons)

A catchy, likeable name can be the difference between wide-reaching notoriety, relative public invisibility, and reactions of disgust to the same organism, and the way this naming power has been used can be both beneficial and incredibly damaging to the conservation of the organism in question. Knowing the significant effect language can have on conservation efforts can be used both by scientists to help guide public opinion towards optimal conservation outcomes, and by the public as consumers and potential supporters of conservation efforts to look at purchasing options and conservation campaigns critically, and determine what the best course of action for them as consumers, citizen scientists, or voters may be.

References

Correia, R. A., Jepson, P., Malhado, A. C. M., & Ladle, R. J. (2017). Internet scientific name frequency as an indicator of cultural salience of biodiversity. Ecological Indicators, 78, 549–555. https://doi.org/10.1016/j.ecolind.2017.03.052

ICUN Red List. (2017). Retrieved January 1, 2017, from http://www.iucnredlist.org

Iglésias, S. P., Toulhoat, L., & Sellos, D. Y. (2010). Taxonomic confusion and market mislabelling of threatened skates: Important consequences for their conservation status. Aquatic Conservation: Marine and Freshwater Ecosystems, 20(3), 319–333. https://doi.org/10.1002/aqc.1083

Logan, C. A., Elizabeth Alter, S., Haupt, A. J., Tomalty, K., Palumbi, S. R., & Snapper Overfished, R. (2008). An impediment to consumer choice: Overfished species are sold as Pacific red snapper. Biological Conservation, 141, 1591–1599. https://doi.org/10.1016/j.biocon.2008.04.007

PETA. (n.d.). Save The Sea Kittens! Retrieved November 20, 2017, from http://features.peta.org/PETASeaKittens/

Sarasa, M., Alasaad, S., Jesú, @bullet, Pérez, M., Sarasa, M., Alasaad, Á. S., … Pérez, J. M. (2012). Common names of species, the curious case of Capra pyrenaica and the concomitant steps towards the “wild-to-domestic” transformation of a flagship species and its vernacular names. Biodivers Conserv, 21, 1–12. https://doi.org/10.1007/s10531-011-0172-3

Wikimedia Commons. https://commons.wikimedia.org/wiki/File:FMIB_50900_Alaska_Pollock.jpeg

Peace through Conservation: The South China Sea

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By Patricia Albano, SRC intern

Spanning an area from Karimata and the Malacca Straits to the Straits of Taiwan, the South China Sea is a marginal sea that is part of the Pacific Ocean and contains 3,500,000 square kilometers of some of the most productive ecosystems on the planet. Bordering this important expanse of water lie many states and territories that are in political conflict for claims to territory in the South China Sea including: China, Taiwan, the Philippines, Malaysia, Brunei, Indonesia, Singapore, and Vietnam. Balancing a scale of massive proportions, the South China Sea serves as a trade hub for one third of the world’s shipping passes, a crucial fishery for the food security of millions of people, and a reserve for oil and gas underneath its crust (Buszynski, 2012) . Because of its strategic political, economic, and ecological position, the area is subject to competing claims for sovereignty by its surrounding nations.

History of the Conflict in the South China Sea

Historically, the South China Sea has been a multi-faceted resource since ancient times. However, the tranquility that the area enjoyed for most of its existence was disturbed in the late twentieth century when a physical occupation of the Spratly Islands (situated around Nansha) took place. Colonization of this zone continued throughout the rest of the century until nearly all of the Spratlys were under littoral control by some surrounding nation-state (Gao & Jia, n.d.). Moving forward, after the United Nations Convention on the Law of the Sea in 1982 established that the Exclusive Economic Zone (EEZ) of a state would extend 200 nautical miles from the continental shelf of the coast of that state, many of the nations surrounding this area laid claim to the same spans of ocean (Image 1). In the case of the Spratly Islands, Taiwan, China, Malaysia, the Philippines, Vietnam, and Brunei have all claimed island territories and EEZ portions. Image 2 depicts the complicated political situation that is found in the South China Sea and how it has been attempted to divide this region.

Map of Exclusive Economic Zones of South China Sea Area (Source: Wikimedia Commons)

Ecological Significance of the Region

Host to a wide diversity of marine organisms, the South China Sea consistently ranks as one of the most rich and biodiverse ecosystems on the planet. The region boasts 571 known species of coral which is comparable to the neighboring Coral Triangle: the globally designated center of maximum marine biodiversity (Huang et al., 2015). However, despite the astounding ecological importance that this region holds, it has gotten little research and conservation attention due to the political conflict surrounding it (Clifton, 2009).

Due to its ideal conditions for life, the South China Sea is home to approximately 400 species of fish. According to the Global International Waters Assessment, the South China Sea ranks 4th among the world’s 19 most productive fishing zones. The villages of the islands surrounding the Sea depend on healthy fishery populations to maintain their source of food and livelihood. Many people living in this region make their entire living off of fishing and hold a very strong stake in the continuing vitality of fish populations. Destructive fishing practices, coral bleaching, and misallocation of resources has created a serious threat to the area. Surrounded by some of the world’s leaders in industrialization and international trade, the South China Sea fishery has fallen victim to economic growth and political disputes over EEZs. Heavy overfishing has led to the decline of adult fish that are only periodically renewed with influxes of pelagic juvenile fish (McManus, Shao, & Lin, 2010). After conducting a study of the connectivity patterns of fish larvae dispersal in 2000-2002, the WorldFish Center concluded that each genetic subgroup of fish in the South China Sea had, at some point, passed through the Spratly Islands. This finding was consistent with the hypothesis that juvenile pelagic fish could be transported from the Spratly Islands area of the region to renew declining populations of fish throughout the entire South China Sea. With this discovery, a call to action for more aggressive marine conservation tactics was born.

Map of Competing sovereignty claims of South China Sea region (Source: Wikimedia Commons)

Peace Through Conservation

Via cooperation in the fields of marine scientific research and environmental protection, progress on preserving this important ecological landmark has moved forward. By proposing a Spratly Islands Marine Peace Park in the South China Sea, the International Union for Conservation of Nature (IUCN) plans to protect this transboundary resource and dedicate it to the preservation of biological diversity and promote peace and cooperation throughout the competing parties involved. Although this location is characterized by disputing sovereignty claims, it is also a region of important waterways, fisheries, tourism, and energy. It is proposed that a Spratly Islands Marine Peace Park in the South China Sea would align with the following five elements: (1) an international board of directors for the park, (2) a contracted management and research institution, (3) a private, secular ranger force, (4) tourism facilities, (5) research facilities and programs (McManus, Shao, & Lin, 2010). By cooperating together, the countries bordering the South China Sea could unite to manifest their interests in this beautiful and essential marine ecosystem and preserve its vitality via research, awareness, and conservation

Works Cited

Buszynski, L. (n.d.). Leszek Buszynski. https://doi.org/10.1080/0163660X.2012.666495 Gao, Z., & Jia, B. B. (n.d.). THE NINE-DASH LINE IN THE SOUTH CHINA SEA: HISTORY, STATUS, AND IMPLICATIONS. Retrieved from https://search-proquest- com.access.library.miami.edu/docview/1346762263?accountid=14585&rfr_id=info%3Axri

CLIFTON, J. (2009). Science, funding and participation: Key issues for marine protected area networks and the Coral Triangle Initiative. Environmental Conservation, 36(2), 91-96. doi:10.1017/S0376892909990075%2Fsid%3Aprimo

Huang, D., Licuanan, W. Y., Hoeksema, B. W., Allen Chen, C., Ang, P. O., Huang, H., … Yeemin, T. (2015). Extraordinary diversity of reef corals in the South China Sea. Mar Biodiv, 45, 157–168. https://doi.org/10.1007/s12526-014-0236-1

John W. McManus , Kwang-Tsao Shao & Szu-Yin Lin (2010) Toward Establishing a Spratly Islands International Marine Peace Park: Ecological Importance and Supportive Collaborative Activities with an Emphasis on the Role of Taiwan, Ocean Development & International Law, 41:3, 270- 280, DOI: 10.1080/00908320.2010.499303

How the complexity of the average marine organism life cycle affects MPA efficiency

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By Elana Rusnak, SRC masters student

Marine Protected Areas, or MPAs, are the global “National Park System” of the ocean.  There are a variety of protection levels, ranging from multi-use zones where certain activities may only be restricted seasonally, to no take-zones where only non-extractive activities are permitted (i.e. SCUBA diving and mooring a boat), and no-use zones, where there are no activities permitted (Science2action.org, 2015).  They are designed to protect a geographic area whose boundaries encompass everything from the surface of the ocean to the ocean floor, and all organisms that live within its borders.  MPAs are theoretically designed to protect ecosystem structure, function, and integrity, enhance non-consumptive opportunities, improve fisheries, and expand knowledge and understanding of marine systems (Stoner et al., 2012).  These jurisdictions are often put in place to protect the habitat of a certain target species, but yield an additional benefit wherein all of the other organisms that live in that species’ habitat are also protected, as long as they stay within the bounds.  For example, a study by Bond et al. in 2017 showed that the establishment of a marine reserve in Belize helped a Caribbean Reef Shark population go from declining (caused by overfishing), to stable over the course of roughly 10 years.

In terrestrial environments, National Parks/Reserves often encompass the entire geographic distribution of a target species.  For example, Yellowstone National Park was used in 1995 to reintroduce the Gray Wolf (Canis lupis) back into the wild, after being hunted nearly to extinction (Philips & Smith, 1997).  They generally live their entire lives within the park, and as such, their population grew to a sustainable level, and they were subsequently taken off the US Endangered Species List in 2008 (USFWS, 2008).

A Map of the various wolf packs within Yellowstone National park, by Yellowstone_wolfmap.jpg: work of a National Park Service employeederivative work: Rrburke (talk) – Yellowstone_wolfmap.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=7770275

Unfortunately, success stories of this magnitude are not often seen in the marine environment for a few different reasons:  MPAs are more difficult to enforce, as they are in a 3D environment where depth is a factor.  This is amplified by the fact that many MPAs are created in countries without the resources to maintain them properly (Bennet & Dearden, 2014).  Moreover, the ocean is an ever-changing environment, with water flow and fluid dynamics having major effects on every ecosystem.  Additionally, a key factor that influences MPA efficacy is the unique life cycle of most marine organisms.  A fundamental difference between organisms on land, and in the ocean, is that marine organisms have larval stages.  Most fish and other marine organisms (corals, invertebrates, etc.) do not give live birth, or hatch their eggs in a stable environment like land animals.  Instead, many reproduce by spawning, which is releasing their millions of eggs and sperm into the water column in hopes they will connect with each other.  Once the eggs are fertilized and the larvae begin developing, they are subject to the forces of nature, and move wherever the current takes them.  They are also more or less microscopic at this point, and are often a food source for larger fish.  Because of this, the larvae of a tuna or blue marlin could be eaten by the very fish that they themselves prey on.  This unique circular pattern, coupled with the fact that larval dispersal can span hundreds of miles in the ocean, makes completely protecting a species in a single MPA very challenging (Cowen et al., 2006).

Queen Conch (Lobatus gigas) by Daniel Neal from Sacramento, CA, US – CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=41777013

According to a study by Cowen et al. in 2006, larval dispersion of coral is affected by many factors, including how long the larvae stay in the water column before attaching to the substrate, directed horizontal/vertical movement of the larvae in the water column, and the adult spawning strategies themselves.  All of these put together result in larval dispersal distances of anywhere from 10-100km.  This dispersal is also seen in the endangered Queen Conch (Lobatus gigas) in the Bahamas.  The Exuma Cays Land and Sea Park is an MPA in the Bahamas, and there is a conch population inside the park that has been shown to be slowly dying of old age. This can be attributed to the fact that larvae are not making it into the park because the population that would be supplying them with larvae is outside of the protected area and is being overfished (Stoner et al, 2012; Kough et al. 2017).  The MPA does not cover the entire geographic distribution of the conch, and therefore, it can be seen that this life-cycle complexity is affecting the efficacy of this protected area.  There have been proposals to create MPA-networks that would protect multiple populations, which may increase larval recruitment (larvae reaching an area and settling down there) and consequently, target species survival.  All of this is evidence that shows we need to approach protecting terrestrial and marine species from different angles, since ecosystem type is clearly not the only fundamental difference between them.

 

References

Bennett, N. J., & Dearden, P. (2014). Why local people do not support conservation: community perceptions of marine protected area livelihood impacts, governance and management in Thailand. Marine Policy, 44, 107-116.

Bond, M. E., Valentin-Albanese, J., Babcock, E. A., Abercrombie, D., Lamb, N. F., Miranda, A., … & Chapman, D. D. (2017). Abundance and size structure of a reef shark population within a marine reserve has remained stable for more than a decade. Marine Ecology Progress Series, 576, 1-10.

Cowen, R. K., Paris, C. B., & Srinivasan, A. (2006). Scaling of connectivity in marine populations. Science, 311(5760), 522-527.

Kough, A. S., Cronin, H., Skubel, R., Belak, C. A., & Stoner, A. W. (2017). Efficacy of an established marine protected area at sustaining a queen conch Lobatus gigas population during three decades of monitoring. Marine Ecology Progress Series, 573, 177-189.

Philips, M. K., Smith, D. W. (1997).  Yellowstone Wolf Project – Biennial Report (1995-1996). National Park service.

Science2action.org, 2015.  Marine Managed Areas: What, Why, and Where. Science to Action.

Stoner, A. W., Davis, M. H., & Booker, C. J. (2012). Abundance and population structure of queen conch inside and outside a marine protected area: repeat surveys show significant declines. Marine Ecology Progress Series, 460, 101-114.

United States Fish and Wildlife Service, 2008.  “Species Profile – Gray Wolf. https://www.fws.gov/home/wolfrecovery/

Declining Sea Ice: Impacts on Arctic Cetaceans

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By Rachael Ragen, SRC intern

Climate change has had a major impact on Arctic waters especially since it is reducing and thinning sea ice. Anthropogenic greenhouse gas emissions have caused the temperature to increase by about 0.2 ºC and almost all of this heat is absorbed by the ocean (Hoegh-Guldberg and Bruno 2010). This negatively impacts the sea ice, which can be problematic for marine mammals since many behaviors are tied to seasonal ice conditions. In March of 1979 there was 16.5 million km2 of Arctic sea ice, but this number decreased to 15.25 million km2 by March of 2009 (Hoegh-Guldberg and Bruno 2010). There are many other effects due to the warming of the oceans. Thermal expansion occurs due to the lowered density of the warmer water causing sea levels to rise. Currents are based upon changes in density due to different temperatures of the water. These may change due to increased warming. The ocean also absorbs excess carbon dioxide from the atmosphere causing ocean acidification, which can have major effects on phytoplankton and zooplankton. This causes problems throughout trophic levels since these organisms make up the basis of many food webs.

Since sea ice is an important factor in the Arctic marine habitat, many marine mammals will experience changes in all aspects of their lives. Some of the most susceptible to these problems are endemic Arctic species such as the narwhal, as they are highly specialized and have trouble altering their habitat. Many other species are thought to shift northward as the temperature continues to increase (Wassmann et al. 2010). The metabolic rates of species also change with temperature and move out of their ideal range (Hoegh-Guldberg and Bruno 2010). The prey of Arctic cetaceans will also be affected by these changes causing a decrease in food and shifts in the food web. The major factor in all of this is sea ice considering the seasonal changes of ice structures the habitat of the marine environment and influences the organisms as well as photosynthetic processes, which have a major impact on the prey of the bowhead whale.

Figure 1: Bowhead whale, (Source: https://upload.wikimedia.org/wikipedia/commons/8/87/A_bowhead_whale_breaches_off_the_coast_of_western_Sea_of_Okhotsk_by_Olga_Shpak%2C_Marine_Mammal_Council%2C_IEE_RAS.jpg)

The bowhead whale is extremely adapted to thick sea ice and can move through nearly solid sea ice cover (Laidre et al. 2008). They rely on copepods and euphasiids but also eat zooplankton as well as pelagic and epibenthic crustaceans (Laidre et al. 2008). Phytoplankton have a specifically timed bloom when the sea ice begins to melt. Zooplankton then feed on these phytoplankton, but if sea ice decreases the water column will be warmed earlier causing the phytoplankton may bloom earlier. This will alter the interaction between zooplankton and phytoplankton possibly having very detrimental effects on the bowhead whale’s major food sources (Laidre et al. 2008).

Figure 2: Beluga (Source: https://c1.staticflickr.com/3/2598/3676156476_e01305bc09_b.jpg)

Belugas are connected with to pack ice and live in waters with a combination of open water, loose ice, and heavy pack ice. (Laidre et al. 2008) As species have a northward shift in their distribution, more predators such as the killer whale could move into the beluga’s habitat. Killer whales prey on narwhals and bowhead whales as well, but it is believed that belugas move into deep, ice-covered waters in order to avoid killer whales. (Laidre et al. 2008) If this ice disappears belugas could lose this protection and become much more susceptible to killer whales.

Figure 3: Narwhal, https://upload.wikimedia.org/wikipedia/commons/4/4e/Pod_Monodon_monoceros.jpg

Narwhals are thought to be the most susceptible of the Arctic cetaceans to changes in sea ice since they are endemic to the Arctic whereas belugas and bowhead whales have a circumpolar distribution (Wassmann et al. 2010). They are highly adapted to pack ice and most of their feeding occurs during winter months in waters with dense pack ice and limited open water. They mostly feed on benthic organisms (Laidre et al. 2008). Decreases or thinning in sea ice could alter their feeding habitats and be detrimental to their prey.

In the end changes in sea ice has many detrimental effects on Arctic cetaceans. As waters warm species are expected to shift northward because they are no longer in their ideal metabolic ranges and their habitats may no longer meet ecological needs (Laidre et al. 2008). Many species such as the humpback whale, minke whale, gray whale, blue whale, pilot whale, killer whale, and harbor porpoises may have altered migration patterns and arrive further north much earlier (Laidre et al. 2008). This will put these species in direct competition with narwhals, belugas, and bowhead whales. Predatory species such as the killer whale may also put more stress on these species due to increased predation. As habitat is lost or altered, the body condition of species will decline. This has a major impact both on cetaceans and prey species. Lowered body condition also makes organisms more susceptible to diseases and epizootics (Laidre et al. 2008). While the decrease in sea ice may initially benefit species like bowhead whales that feed on photosynthetic plankton, it will have unknown effects on the food web. The benefits will likely be short lived and become more detrimental to the habitat (Laidre et al. 2008).

References

Hoegh-Guldberg O, Bruno JF (2010) The impact of climate change on the world’s marine ecosystems. Science 328:1523-1528

Laidre KL, Stirling I, Lowry LF, Wiig O, Heidi-Jorgenson MP, Ferguson SH (2008) Quantifying the sensitivity of arctic marine mammals to climate-induced habitat change. Ecol Appl 18:97-125

Wassmann P, Duarte CM, Agustí S, Sejr MK (2011) Footprints of climate change in the Arctic marine ecosystem. Glob Chang Biol 17:1235-1249

Epibionts and Sea Turtles

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By Grant Voirol, SRC intern

Sea turtles are notoriously difficult to study due to their large size and highly migratory behavior. However, a new technique is being utilized to help shed light on their habitat use and migration patterns. When looking at a sea turtle, oftentimes you are not just looking at a sea turtle. What you are looking at is an extensive community of micro and macro organisms that participate in complex interactions (Caine, EA 1986). Attached to the surface of the turtle’s shell are a wide variety of organisms that spend their entire lives traveling the seas with their turtle captain. These organisms, known as epibionts, are each a small piece of the puzzle that can be used to give us a more complete picture of the movement preferences of many species of sea turtles.

By Jun V Lao  [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons

Epibionts on sea turtles come from a variety of taxa and can range widely in size. Algae, tiny crustaceans, and barnacles of different species can be found on all seven different types of sea turtles and exert a wide range of effects. Barnacles growing on the turtle’s carapace might increase the drag felt my the turtle, making it expend more energy to more through the water but also provide it with camouflage while it rests on the ocean floor. Additionally, other epibionts may feed off of the parasitic epibionts benefitting the turtle (Robinson et al. 2017).

While describing the community structure of these hitchhikers is interesting, we can gain other useful information from them as well. By using just one species, the flotsam crab Planes major, a small crab ranging from 1-2 cm, scientists were able to gain better understanding into the amount of time different turtle species spent near the surface (Pfaller et al., 2014). Using three turtle species, loggerhead, green, and olive ridley, the study found that each species holds significantly different amounts of crabs on their backs. This suggests that the turtles are using their habitats in different ways. The flotsam crab is generally found in surface waters where it makes its home on (as its name implies) flotsam, drifting through the ocean. Therefore, green turtles, which were found to have a very low frequency of flotsam crab on their shell, most likely don’t spend much time at surface waters but mostly stay near the bottom to forage. Similarly, olive ridleys and loggerheads, which were found to have a high frequency of flotsam crab, most likely spend much of their time near the surface (Pfaller et al. 2014).

But this study was conducted using turtles from multiple different areas, what if that had a factor in the results? Another recent study proved that this most likely is not the case. Testing three species of turtles, green, olive ridley, and leatherback, from one nesting location in Costa Rica and using multiple different species of epibionts, it was concluded that each species of turtle does have its own unique community of epibionts (Robinson et al. 2017). All turtles sampled in the study came from the same beach yet exhibited large differences in epibiont diversity.  Leatherbacks, which forage far into the open ocean, were found to have much lower epibiont diversity than the other two species. This makes sense, as the environment that they spend most of their time in is largely uniform. Olive ridleys and green turtles, which occupy varying habitats of the open ocean as well as coastal waters, were found to have an increased level of epibiont diversity. Furthermore, certain epibionts were only found on one species of turtle (Robinson et al. 2017).

Barnacles encrusted on a sea turtle By U.S. Fish and Wildlife Service Southeast Region (Barnacles on Carapace Uploaded by AlbertHerring) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0) or Public domain], via Wikimedia Commons

All of this gives credence to the use of epibionts for habitat and migratory use. Sea turtles use such large habitats, that it is difficult and expensive to attach satellite trackers to large numbers of them. Epibionts can be used as miniature tags, showing us where a turtle has been. Say an epibiont that is only found in a certain area is found on the back of turtle, then we know that the turtle has visited that area recently. This is important for fisheries management. One of the main causes of turtle mortality is from bycatch, when fishing boats catch nontarget species and they die in the process (Wallace et al. 2011). Now that we can gain more and more information about their migratory habits, we are better able to identify hotspots that turtles are likely to visit in their travels and properly protect them. We can also now do this affordably, as no tags need to be used. With this new technique we can help to better protect sea turtles with the help of these little creatures.

References

Caine E.A. (1986). “Carapace epibionts of nesting loggerhead sea turtles: Atlantic coast of U.S.A.” Journal of Experimental Marine Biology and Ecology, 95, 15-26.

Pfaller, J. B., Alfaro-Shigueto, J., Balazs, G. H., Ishihara, T., Kopitsky, K., Mangel, J. C., … Bjorndal, K. A. (2014). “Hitchhikers reveal cryptic host behavior: New insights from the association between Planes major and sea turtles in the Pacific Ocean.” Marine Biology, 161(9), 2167–2178.

Robinson, N. J., Lazo-Wasem, E. A., Paladino, F. V., Zardus, J. D., & Pinou, T. (2017). “Assortative epibiosis of leatherback, olive ridley and green sea turtles in the Eastern Tropical Pacific.” Journal of the Marine Biological Association of the United Kingdom, 97(6), 1233–1240.

Wallace, B. P., C. Y. Kot, A. D. DiMatteo, T. Lee, L. B. Crowder, and R. L. Lewison. (2013). “Impacts of fisheries bycatch on marine turtle populations worldwide: toward conservation and research priorities.” Ecosphere 4(3), 1-49.

A Story of Dramatic Conservation Effort: Saving the Vaquita Porpoise (Phocoena sinus) from Extinction

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By Chelsea Black, SRC intern

It has been clear for several years that the vaquita porpoise (Phocoena sinus) is in danger of extinction, but only recently has the plight of this species received global attention. The vaquita is the most critically endangered marine mammal in the world and is endemic to the northern Gulf of California, Mexico (Rojas-Bracho, Reeves & Jaramillo-Legorreta, 2006). Genetic analyses and population simulations suggest that this species has always maintained a small population size (Rojas-Bracho et al., 2006), but accidental deaths caused by gillnet fishing gear have been the primary reason for their rapid demise (Jaramillo-Legorreta et al., 2007). Between the years of 1997 and 2015, the species experienced a population decline of 92% (Taylor et al., 2017). Population assessments estimated the population size of the vaquita to be at an alarming number of 60 in 2015, which then dropped to a total of 30 individuals by 2017. Over the past three years there have been dramatic efforts to save the vaquita from what seems like their inevitable extinction, which could be as early as 2018 according to the World Wildlife Fund.

Local fishermen in Mexico’s Gulf of California target the critically endangered fish, totoaba (Totoaba macdonaldi), for its swim bladder. The swim bladder is considered a delicacy in parts of Asia, selling for as much as $10,000 per kilogram (Mosbergen, 2016). It is in these gillnets meant to capture totoaba that vaquita become bycatch and eventually drown. In 2016, the International Whaling Commission approved emergency measures to permanently ban gillnet fishing from the vaquita’s range, remove existing gillnets, and suppress the illegal trade of totoaba (Mosbergen, 2016). However, scientists fear the removal of gillnets is not sufficient enough to save the remaining vaquitas, considering their extremely low population numbers. In response, active measures have been taken in an attempt to help save the species.

In June 2017, Mexico announced plans to use trained dolphins to help corral the remaining porpoises into a protected breeding sanctuary (“Mexico to use Dolphins,” 2017). The dolphins, previously trained by the US Navy to search for missing SCUBA divers, are trained to locate and herd the vaquitas to a marine refuge where they would ideally repopulate in safety. Unfortunately, the use of trained dolphins was not successful. The government then put together a team of marine mammal experts to go into the field and capture as many vaquitas as possible. To help with the conservation of the vaquita, the Mexican government created the Consortium for Vaquita Conservation, Protection, and Recovery (VaquitaCPR) to implement an action plan to prevent the extinction of the species. This plan is arguably the most dramatic conservation effort to date, but scientists are skeptical of how successful the program will be.

The rescue plan of VaquitaCPR includes four phases. Phase one involves locating and rescuing individuals followed by an evaluation of their suitability for human care. Phase two involves housing the vaquita in a marine sanctuary where, during phase three, the vaquitas breed in captivity. Finally, phase four is the release of the individuals back into the wild, and the ultimate goal of the entire project (“Rescue Efforts”).

In October 2017, Mexico announced the successful capture of a six-month old vaquita calf that was quickly released back into the wild because it was still dependent on its mother. This was the first ever capture of a vaquita, and left scientists optimistic that the goal of the VaquitaCPR team was indeed feasible (“New Recovery Project,” 2017). With a successful capture under their belt, the team of marine mammal experts set out to capture another vaquita, with the hopes of transporting it into the reserved area. 

Figure 1: The first capture of a vaquita (source: vaquitaCPR.org)

In early November 2017, the VaquitaCPR team caught a second vaquita, but unfortunately this was not a success story. The mature female was captured and transported to a floating sea pen where veterinarians determined the animal was under extreme stress, and despite life-saving efforts the vaquita died within a few hours (Gaworecki, 2017). With such few individuals left, the loss of a female of reproductive-age is one of catastrophic proportion. Currently, the VaquitaCPR project has ceased all active measures to capture vaquitas, without ever successfully reaching phase two of their initial rescue plan.    

Figure 2: Floating sea pen for captured vaquitas (source: Kerry Coughlin/National Marine Mammal Foundation).

The unfortunate truth could be that the vaquita porpoise is too stress-intolerant to endure capture and transportation, and this would make rebuilding their population in captivity impossible. Conservation efforts to save the remaining vaquitas will shift to removing all gillnets from their habitat, and a stricter enforcement of the illegal fishing of totoaba. The number of boats setting these particular gillnets in the vaquita’s range is minimal, and with the new permanent ban set by the Mexico government, hopefully these mitigations are sufficient to relieve pressure on the species. The success or failure of saving the vaquita from the brink of extinction will be a precedent in marine mammal conservation.  

References

Gaworecki, M. (2017, November 08). Endangered Mexican Vaquita Dies After Rescue Effort. Retrieved November 20, 2017, from https://www.ecowatch.com/vaquita-dies-after-rescue-effort-2507794284.html

Jaramillo-Legorreta, A., Rojas-Bracho, L., Brownell Jr, R. L., Read, A. J., Reeves, R. R., Ralls, K., & Taylor, B. L. (2007). Saving the vaquita: immediate action, not more data. Conservation Biology, 1653-1655.

Mexico to use dolphins to save endangered vaquita porpoise. (2017, July 1). Retrieved November 20, 2017, from https://phys.org/news/2017-07-mexico-dolphins-endangered-vaquita-porpoise.html

Mosbergen, D. (2016, December 28). ‘Risky’ Last-Ditch Attempt To Save The World’s Smallest Porpoise. Retrieved November 20, 2017, from https://www.huffingtonpost.com/entry/vaquita-mexico-capture-plan_us_58635c2be4b0de3a08f69948

New recovery project captures vaquita porpoise calf. (2017, October 20). Retrieved November 20, 2017, from http://mexiconewsdaily.com/news/new-recovery-project-captures-vaquita-calf/

Rescue Efforts. (n.d.). Retrieved November 20, 2017, from https://www.vaquitacpr.org/rescue-efforts/

Rojas-Bracho, L., Reeves, R. R., & Jaramillo-Legorreta, A.  (2006). Conservation of the vaquita Phocoena sinus. Mammal Review, 36(3), 179-216.

Taylor, B. L., Rojas‐Bracho, L., Moore, J., Jaramillo‐Legorreta, A., Ver Hoef, J. M., Cardenas‐Hinojosa, G., … & Thomas, L. (2017). Extinction is imminent for Mexico’s endemic porpoise unless fishery bycatch is eliminated. Conservation Letters, 10(5), 588-595.

How Marine Reserves Can Help Preserve Ecosystems by Reducing Bycatch

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By Jess Daly, SRC Intern

One of the greatest environmental impacts of industrial fisheries is the accidental removal of species in bycatch. Many fisheries have a single target species that they look to catch when they fish. Any other species that pull up in their nets or on their lines are known as bycatch. These fish are often simply discarded since the fisherman will not make money off them, even though they may be of great importance to the ecosystem. Bottom trawling is one type of fishing that involves dropping weighted nets to the bottom of the ocean and dragging them along the sea floor. Nearly 23% of fisheries use trawl nets as their primary fishing method, which is criticized both for its very high bycatch percentage (anything on or near the bottom will be pulled up in the net) as well as the destruction of corals colonies from the weights being dragged across them (Van Denderen et al, 2016). Other kinds of fishing nets, such as midwater trawls and driftnets, also typically have high bycatch percentages.

Figure 1: This illustration shows what a bottom trawl fishing net looks like as well as how it works. Source: Mr. Bijou, Blogspot

Bycatch is a serious problem, but not one that is easy to solve because of limitations of fishing equipment and the inherent difficulty of trying to fish for a single species. Traditional methods of reducing bycatch, such as limiting the total number of fish that can be taken, can be difficult to enforce and are economically costly for the fisherman (Hastings et al, 2017). Using specialized fishing gear is a second potential method, but can also be quite expensive and is not always effective. Recently, the concept of using marine reserves as a tool to help reduce bycatch has begun to gather interest. Marine reserves are areas that are designated “no-take,” meaning that nothing can be removed from the area. Fishing, bottom trawling, and taking of shells are among the activities that are not allowed inside the reserve. They are usually areas that are of great importance to fish species for a specific reason, such as a mating grounds or nursery. It has been shown in multiple studies that marine reserves cause increases in fish populations and can help depleted species to recover their numbers (Mumby and Harborne, 2011). Large female fish are exactly the type that fisherman hope to catch, so without protection they are fished out quickly and the population declines because they are not reproducing. Inside a no-take area, however, female fish can grow larger and thus produce larger, healthier offspring. The population increases and eventually flourishes, maintaining the health of the ecosystem and the fisheries’ profits simultaneously.

Figure 2: The waters off Anacapa Island, California are one example of a marine reserve, or “no-take zone”. The map shows the reserve area in red. Source: Matt Holly, National Parks Service

In some fisheries the primary bycatch species, also known as the weak stock, are slow to mature, have long lifespans, and produce fewer offspring than target species. Some fishing practices intended to maximize target species catch may decimate the weak stock and wreak ecological havoc (Hastings et al, 2017). A 2017 study conducted by Drs. Hastings, Gaines, and Costello used extensive mathematical modeling to examine the potential effects of marine reserves on fisheries. They found that in every case where the weak stock was a species with a longer life expectancy and lower reproduction rate than the target species, marine reserves increased target species yield more than other management methods. They also showed that creating no-take zones specifically designed to protect bycatch species did not decrease the maximum yield of the target species (Hastings et al, 2017).

In the first case the marine reserves increase target species yield because there is no limit on specific catch numbers, and also because they protect areas of great importance to the fish. If this area is a breeding ground or nursery, this protection results in more offspring being produced and then going on to survive to adulthood. If there are more fish in the water, more of them can be caught without damaging the population or the ecosystem. In the second case, where the marine reserve is specifically tailored to protect the bycatch species, the target species catch does not decrease significantly because the fish share a habitat. Even if the protected area is not of special importance to the target species, the fish still live in that area. If they cannot be caught inside the reserve, their numbers can increase and are able to offset extra fish that might be taken from outside the reserve.

While it may seem that completely prohibiting fishing in high-production areas would lead to decreases in fisheries profits, there is strong evidence that marine reserves effectively and cost-efficiently maintain profit margins while mitigating the economical damage of many fishing practices. By protecting bycatch species and limiting the number of unwanted fish that are removed from the ocean, ecosystems can better withstand fishing pressures and better recover from past overfishing trauma.

Works Cited

Hastings, Alan, et al. “Marine Reserves Solve an Important Bycatch Problem in Fisheries.” Proceesings of the National Academy of Sciences of the United States of America, vol. 114, no. 34, 22 Aug. 2017, pp. 8927–8934, www.ncbi.nlm.nih.gov/pmc/articles/PMC5576807/.

Mumby, Peter J., and Alastair R. Harborne. “Marine Reserves Enhance the Recovery of Corals on Caribbean Reefs.” PLOS ONE, Public Library of Science, 11 Jan. 2010, journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0008657.

Van Denderen, Pieter Daniël, et al. “Using Marine Reserves to Manage Impact of Bottom Trawl Fisheries Requires Consideration of Benthic Food-Web Interactions.” Ecological Applications, vol. 26, no. 7, 2 Sept. 2016, orbit.dtu.dk/ws/files/123769828/Postprint.pdf.

Holly, Matt. “Anacapa Island Map.” Wikimedia Commons, National Parks Service, 25 Feb. 2016, commons.wikimedia.org/wiki/File:NPS_anacapa-island-map.jpg.

“Mr. Bijou”. “How Bottom Trawling Works.” Oceans Become Deserts, Blogspot, 10 Jan. 2006, misterbijou.blogspot.com/2006/01/.

Disrupting a Biological Clock: Ticking Away Towards Further Environmental Contamination

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By Casey Dresbach, SRC Intern

In an anthropogenic epoch, where industrial growth has become evermore prolific, threats of disturbance continue to change the environment. Some of these disturbances include habitat destruction and pollution, both of which threaten biodiversity and healthy ecosystems worldwide. (Palumbi, 2001; Dudgeon et al., 2006; Sih, Ferrari, & Harris, 2011). Fortunately, organisms may be able to adapt to changes in their environment to cope with this territorial renovation. These adaptations allow for species to persist under conditions that are polluted by destructive contaminants. However, such adaptation can also be associated with unforeseen tradeoffs that can actually pose consequential threats to a species’ existence. Reduced reproduction, smaller body sizes or increased susceptibility to other environmental stressors are just a few of these repercussions. (Ghazy, Habashy, Kossa, & Mohammady, 2009; Jansen, Stoks, Coors, van Doorslaer, & de Meester, 2011; Latta, Weider, Colbourne, & Pfrender, 2012)

Salinization of certain freshwater environments is, unfortunately, a frequent modern trend. Inherent from sources such as seawater intrusion, mining, and road salt, such disturbance has already forced many organisms into adaptive measures. Road salt, also known as NaCl, is commonly used in northern climates to clear streets and sidewalks of snow; it works as a de-icing aid (Learn, 2017). Continuous research efforts are aimed at the consequences of where the salt is ultimately absorbed in the seasons to follow once the climate warms up again. Road salt does not simply dissolve into the air, but instead splits into sodium and chloride ions that are then absorbed by roadside plants, and ultimately find their way into freshwater environments. (Godwin, Hafner, & Buff, 2002).

Zooplankton are especially important in freshwater ecosystems because they are both primary feeders on phytoplankton and a food source for other small fish. When looked at on a food chain, it is evident that they are essential to stabilizing an ecosystem. (See Figure 1) Ecosystem services are the material or energy outputs of an ecosystem that can benefit humans and other life. Some of these services may include food, water, and other resources (Teeb Web, n.d.).

Figure 1. Oceanic ecosystem showing zooplankton as primary feeders on phytoplankton, showing the species as both the predator and the prey. (Belle Isle Conservancy, 2017).

In a recent study, an important species of zooplankton, Daphnia pulex was carefully studied within the context of their increasing tolerance to road salt, a common contaminant. As their freshwater habitats become saltier, Daphnia, among many other species, are forced to adapt at the expense of some of their regulatory genes. Researchers found that this salinization disturbance causes a major disruption in their circadian rhythm, a 24 hour cycle in the physiological process of living organisms, including plants, animals, fungi and cyanobacteria (Science Daily, 2017). By looking at a certain regulatory gene called period, they found suppressed, or as they called it “ablated”, levels of the gene’s oscillation. Unlike period, several other genes showed higher levels of expression indicating staggering increases in adaptation to high levels of salinity in these freshwater habitats. So unfortunately, while several other genes were adapting to new standards, the putative clock gene, period, was suppressed, meaning the circadian rhythm of the Daphnia species was minimized.

Daphnia pulex is an example of a species that is highly capable of adapting – evident in several of their genes, including, clock, actin, and the gene that regulates Na+/K+-ATPase. The species is also a prime example of overcompensation; capable of adaptation yes, but at the expense of an important regulatory gene. As mentioned earlier, a disturbance such as habitat destruction can affect reproduction, growth, longevity, and other behaviors such as diel vertical migration (DVM), a daily mass movement of zooplankton to the sea surface (Coldsnow, Relyea, & Hurley, 2017). In general it describes migrations upward at dusk and downward around dawn. During this migration, organisms migrate towards the surface at night to feed and then back down the water column during the day to minimize predation. By remaining at depth during the day in dimly lit water and ascending at night, they minimize their vulnerability to visual predators. The period gene is used as an external cue as to when zooplankton should migrate to feed. If that gene is suppressed, their circadian rhythms will be offset. A decline in Daphnia results in an increase in the trophic level above, as well as a loss of ecosystem services (See Figure 2).

Figure 2. Zooplankton’s 24-hour migration cycle known as Diel Vertical Migration (DVM). (Planktoneer, 2008).

This study is an important initiative in a world of increasing anthropogenic disturbances. Urbanization will continue to change the natural world and, unfortunately, so will its detrimental consequences. More research should be done to investigate further implications in regards to environmental changes.

References

Belle Isle Conservancy. (2017). Food Chains. Retrieved from Detroit Aquarium: (https://detroitaquarium.weebly.com/uploads/2/5/7/5/25755066/editor/ocean-ecosystem-in-bali-8-638.jpg?1489083980)

Coldsnow, K. D., Relyea, R. A., & Hurley, J. M. (2017, October 28). Evolution to environmental contamination ablates the circadian clock of an aquatic sentinel species. (Wiley, Producer) Retrieved from Wiley Ecology and Evolution: http://onlinelibrary.wiley.com/doi/10.1002/ece3.3490/epdf

Godwin, K. S., Hafner, S. D., & Buff, M. F. (2002, December 5). Long-term trends in sodium and chloride in the Mohawk River, New York: the effect of fifty years of road-salt application. Environmental Pollution.

Learn, J. R. (2017, May 26). The Hidden Dangers of Road Salt. Retrieved from Smithsonian : https://www.smithsonianmag.com/science-nature/road-salt-can-disrupt-ecosystems-and-endanger-humans-180963393/

Planktoneer. (2008). Forays and Foraging in Marine Zooplankton. Cambridge, MD, USA.

Science Daily. (2017). Circadian Rhythm – Reference Terms. Retrieved November 10, 2017, from Science Daily: https://www.sciencedaily.com/terms/circadian_rhythm.htm

Teeb Web. (n.d.). Ecosystem Services. Retrieved November 10, 2017, from The Economics of Ecosystems & Biodiversity (TEEB): http://www.teebweb.org/resources/ecosystem-services/

An Examination of Intraguild Predation Events Between Sharks and Pinnipeds or Cetaceans, and Their Importance

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By Brenna Bales, SRC intern

Popular opinion conjectures that sharks are always the dominant predator in their specific environments. The famous, terrorizing shot of the great white shark leaping out of the water with the unsuspecting seal in its jaws is iconic to Discovery Channel’s “Shark Week” highlight reel every year, boosting this notion of shark dominance. But what many don’t realize is that the seal is more capable than it may seem in those dramatized, slow-motion clips; In some cases, the role may be reversed.

Intraguild predation (IGP) is the killing or consuming of species that are also potential predators, a combination of both competitive and parasitic/predatory interactions (Polis et. al., 1989). What is so special about this type of relationship between two species? Fundamentally, the act of killing a predator and using it as a source of energy impacts more than just the two species directly involved. Instead, it affects other populations indirectly, and can stabilize or destabilize an environment in different ways. For example, population declines based on age differences can occur, as a species A adult will predate over a species B adult; However, a species A juvenile is preyed upon by a species B adult (Polis et. al., 1989; Figure 1). If there are less species A juveniles due to predation, then there will subsequently be less species A adults, thus reducing threats on species B at all ages. These changes trickle down the trophic levels, affecting species A and B prey items and their respective food sources, as changes in apex predator populations have cascading trophic effects (Myers et. al., 2007).

Figure 1: Three types of intraguild predation: (a) simple, (b) reciprocal, (c) reciprocal age-dependent.
https://openi.nlm.nih.gov/imgs/512/178/2853694/PMC2853694_442_2010_1575_Fig1_HTML.png

Overall, IGP can be age-, density-, and resource-dependent, disturbing established trophic and population dynamics such as above. There are two IGP descriptors, each with two categories: symmetry (asymmetrical/symmetrical) and age structure (important/relatively unimportant) (Polis et. al., 1989). We will first examine an asymmetrical IGP event. Observations by Chris Fallows in waters off Cape Point, South Africa led to the discovery of the predation of Cape fur seals (Arctocephalus pusillus pusillus) on blue sharks (Prionace glauca). This is the first evidence of asymmetric IGP on a mid-sized predatory shark by a pinniped (Fallows et. al., 2015). Therefore, these observations were exciting. The seal only consumed the viscera (main internal organs such as intestines, stomach, liver, etc.) after chasing and tossing the shark for several minutes (Figure 2). It proceeded to perform similar actions and kill 5 out of 10 sharks in the vicinity. This behavior is significant because in the past, the opposite interactions have been observed, in which adult blue sharks chased juvenile and adult Cape fur seals (Stewardson 1999). This behavior is similar to the situation between species A and B explained above; Although, in the end, not enough evidence is presented to strictly attribute age-dependency to the relationship between blue sharks and Cape fur seals.

Figure 2: A Cape fur seal feeds on a blue shark. Taken from: Fallows, C., Benoît, H.P. and Hammerschlag, N., 2015. Intraguild predation and partial consumption of blue sharks Prionace glauca by Cape fur seals Arctocephalus pusillus pusillus. African Journal of Marine Science, 37(1), pp.125-128.

Another first for shark-pinniped IGP observations was an incident off the coast of New South Wales, Australia. An Australian fur seal (Arctocephalus pusillus doriferus) was observed feeding on an approximately 1.4-meter wobbegong shark (Orectolobus ornatus) (Allen and Huveneers, 2005). It was inferred that the incident was predatory due to the fact that the shark’s bodily condition would have appeared different had it been opportunistically ripped off a hook from a long-line, and rejection by a fisherman was unlikely. In addition, wobbegong sharks have never been found in the diet of any other predatory animal, although elasmobranchs such as the puffadder shyshark (Haploblepharus edwardsii) and the spiny dogfish (Squalus acanthias) have been (Allen and Huveneers, 2005). This supports the need to examine changing predatory roles in marine environments, as more than one threatened species at the top of the food chain can have serious conservation implications, and the removal of one species may have consequences not previously considered.
Switching from pinnipeds to cetaceans, recently popularized killer whale (Orcinus orca) and great white shark (Carcharadon carcharias) interactions have flipped the public’s vision of the great white as the ocean’s most fearsome predator. However, these interactions have been observed and officially recorded since the 1990’s around the Farallon Islands by researchers such as Peter Pyle and Scott Anderson. Both species consume pinniped prey, and the killer whales will occasionally consume the white sharks, clearly an example of IGP (Pyle et. al., 1999), and one that contradicts long-held beliefs.

There are two cases in which the same type of IGP interactions have different outcomes: when prey is abundant, and when it is not. If resources are abundant, competition will be low, and species A and B will, for the most part, coexist. However, when the situation is reversed and prey resources are limited, species A may begin to prey upon species B, thus becoming an IGP situation. The major sharks that are thought to prey on cetaceans are the white shark (Carcharadon carcharias), tiger shark (Galeocerdo cuvier), bull shark (Carcharhinus leucas), sixgill shark (Hexanchus griseus), sevengill shark (Notorynchus cepedianus), dusky shark (Carcharhinus obscurus), oceanic whitetip shark (Carcharhinus longimanus), shortfin mako shark (Isurus oxyrinchus), pacific sleeper shark (Somniosus microcephalus), greenland shark (Somniosus microcephalus), cookie-cutter shark (Isistius brasiliensis), and portugese dogfish (Centroscymnus coelolphis) (Heithaus 2001). However, reciprocal predation/consumption by cetaceans on these species is rare to non-existent, although aggression is often observed from both cetaceans and pinnipeds (Heithaus 2001; Stewardson and Brett, 2000; Kirkwood and Dickie, 2005).

In conclusion, unexpected intraguild predation between different species is dependent on a variety of environmental, opportunistic, and resource related variables, and expands beyond the marine environment (Polis et. al., 1989). As declines of elasmobranch, pinniped, and cetacean populations continue, lower trophic levels may or may not even be affected when other species subsequently become dominant predators, with only the upper trophic levels being affected. Nonetheless, these are important considerations to factor into an ecological assessment or examination, as climate and anthropogenic stressors mount on wild populations.

Literature cited:

Allen, S. and Huveneers, C. (2005). First record of an Australian fur seal (Arctocephalus pusillus doriferus) feeding on a wobbegong shark (Orectolobus ornatus). Proceedings of the Linnean Society of New South Wales 126, 95-97.

Bowen WD, Iverson SJ. 2013x. Methods of estimating marine mammal diets: a review of validation experiments and sources of bias and uncertainty. Marine Mammal Science 29: 719–754.

Fallows, C., Benoît, H.P. and Hammerschlag, N., 2015. Intraguild predation and partial consumption of blue sharks Prionace glauca by Cape fur seals Arctocephalus pusillus pusillus. African Journal of Marine Science, 37(1), pp.125-128.

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