Atypical and Estuarine Habitat of the Maroni River Mouth Altering Green Turtle Behavior in French Guiana

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By Casey Dresbach, SRC intern

Green Sea Turtle, Chelonia mydas. (Your Shot National Geographic, 2013) http://yourshot.nationalgeographic.com/photos/2387735/?source=gallery)

Green Sea Turtle, Chelonia mydas.
(Your Shot National Geographic, 2013) http://yourshot.nationalgeographic.com/photos/2387735/?source=gallery)

 

In this experiment, satellite telemetry was used to assess the behavioral adjustments of twenty-six adult female green turtles. Sixteen Argos-linked Fastloc GPS tags were deployed on green turtles from February to June 2012 on both sides of the Maroni River: Awale-Yalimpo and in the Galibi Nature Reserve in Suriname. At the same time, ten other females in the Amana Nature Reserve were equipped with Conductivity-Temperature-Depth-Fluorometer Satellite Relayed Data Loggers, which provided the locations of the turtles via Argos data, and recorded profiles of the dive depth, time at depth, dive duration and post-dive surface interval, and oceanographic data in the form of vertical temperature and salinity profiles taken during the rising phase of these turtles’ dives as seen in Figures 1 and 2. The intent of tagging was to analyze three entities: home range, diving behavior, and environmental conditions.

Figure 1. Extreme temperatures recorded in-situ by the Argos-Linked Fastloc GPS tags on green turtles Chelonia mydas of 2012.) (Chambault, et al.)

Figure 1. Extreme temperatures recorded in-situ by the Argos-Linked Fastloc GPS tags on green turtles Chelonia mydas of 2012. (Chambault, et al.)

Temperature-salinity diagram for the green turtles tagged with a CTD-SRDL tag in 2014. (Chambault, et al.)

Temperature-salinity diagram for the green turtles tagged with a CTD-SRDL tag in 2014. (Chambault, et al.)

In relation to home range, the findings show that Chelonia mydas stayed close to both the shore and their nesting beach, exhibiting limited movement. By staying close to shore, the turtles are likely to save energy for oviposition, the act of laying their eggs. Regarding diving behavior, dive data showed that individual female green turtles were spending extended periods at the surface. This may be related to their highly diurnal resting activity, where they are active during the day. The data also shows that these turtles went for short and shallow dives. One of the reasons for this suggests basking at the surface, which can be beneficial for thermoregulation, especially in these warmer waters. Also, this behavior permits the avoidance of aggressive males or potential predators, delay of algal or fungal infestations, and also an enhancement of immune response. Additionally, spending time at the surface is associated with both their lungs’ positive buoyancies (being denser than water surrounding it) as well as foraging activity. In terms of finding food, a green turtle’s preferred choice of sustenance is seagrass. However, the waters of the French Guiana provide an extreme environment for these turtles, where large river outputs generate very warm water (~27 to 29° C) and highly variable salinities (1.2 to 35.5 psu), as shown in Figures 1 and 2. In these waters, the high river outflow lead to low levels of irradiance, probably resulting in the lack of seagrass. The turtles of the French Guiana have adapted to this consequence by seeking alternate food sources and also relying on stored body fat for energy, defining the population as capital breeders. Adaptations are often compromises; each organism must do many different things to compensate for their surroundings (Reece, Urry, Cain, Wasserman, & Minorsky, 2014). We humans owe much of our versatility to our flexible limbs, but they are also prone to sprains, torn ligaments, and dislocations. Hence, structural reinforcement has been compromised for agility. These turtles are compromising their preferred food choice because it is unavailable. Their available alternatives include those befitting the water’s turbid environment such as: crustaceans, polychaete worms, and cnidarians. Jellyfish are fairly abundant on the French Guiana continental shelf, and these female turtles are adapting an appetite for an alternative source of nutrition to enable survival.

This study provides the first data to describe the inter-nesting events, habitat use, dispersal and diving behavior of green sea turtles. The findings show this population of Chelonia mydas has adapted many behaviors in response to the deviant and estuarine habitat of the Maroni river mouth. This is the first study to track this specific population of green turtles during their inter-nesting season. Satellite tracking made it possible to locate and quantify the habitat used by Chelonia mydas during their inter-nesting seasons. Their survival is at risk, both with increasing climate change and the life-threatening illegal fishing along the Guiana coast. By evaluating their home range, it makes it possible to obtain a reliable visual of areas where these turtles nest, to thus identify hotspots that need protection. The endangered species is particularly vulnerable during their inter-nesting periods, especially in the atypical environment they are residing in. Further research should be done to evaluate the interactions between green turtles and fisheries to ultimately seek permission to delineate a Marine Protected Area.

Works cited

Chambault, P., Thoisy, B. d., Kelle, L., Berzins, R., Bonola, M., Delvaux, H., et al. (2016). Inter-nesting behavioural adjustments of green turtles to an estuarine havitat in French Guiana. Marine Ecology Progress Series , 555: 235-248 .

Dunand, A. (2013, October 15). Your Shot National Geographic .

Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., & Minorsky, P. V. (2014). Campbell Biology . Boston: Pearson.

Nocturnal migration reduces exposure to micropredation in a coral reef fish

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By Josh Ratay, SRC intern

The French grunt was used as the organism of study, though gnathiid isopods feed on many different species of reef fish. Image from Wikimedia Commons.

The French grunt was used as the organism of study, though gnathiid isopods feed on many different species of reef fish. Image from Wikimedia Commons.

 

Nocturnal migration reduces exposure to micropredation in a coral reef fish is a new study examining daily migrations of French grunt (Haemulon flavolineatum) and the exposure to parasitic isopods. French grunts are known to move off the reefs and into seagrass beds at night. Such behavior in animals is usually attributed to increased availability of prey or decreased exposure to predators. However, this study investigates the idea that the fish’s movements may serve as a method of avoiding isopods, which are far more common on the reefs than in seagrass communities.

The French grunt served as an ideal model organism for this study since it is both extremely common and well-studied on Caribbean reefs. However, many other reef fish are known to undertake similar nightly migrations away from the reef. Gnathiid isopods are tiny parasitic crustaceans which attach to fish and feed on blood. Though they usually hide in reef sediments, the larvae emerge to find a short-term host fish directly before molting and growth. Though far smaller than their hosts, these parasites can have many negative health impacts on fish, including decreased concentrations of red blood cells, tissue damage and infection, and even the death of juvenile fish which are exposed to a high isopod load.

Larval gnathiid isopods (bottom right) feed on the blood of fish before molting. Adult males (left) and females (right) tend to remain in the sediment. Image from Wikimedia Commons.

Larval gnathiid isopods (bottom right) feed on the blood of fish before molting. Adult males (left) and females (right) tend to remain in the sediment. Image from Wikimedia Commons.

In this study, several tests were performed at different locations in the Caribbean to test the hypothesis that leaving the reef at night results in fewer numbers of isopods infesting French grunts. Cages containing 5 to 8 fish were deployed overnight at both reefs and nearby seagrass habitats where grunts had been observed. Also, the exact arrival times (around dawn) of the wild grunts to the reefs were observed at different sites, and cages of grunts were subsequently placed at the reefs for both the 30 minutes preceding the arrival time and 30 minutes following the arrival time. The goal of this test was to investigate whether or not the fish’s arrival time coincided with lessened isopod activity. Additional cages were also deployed to test day versus night isopod levels, and the whether or not juvenile grunts were also susceptible to isopod infestation. All fish from the cages were placed in seawater tanks, where the isopods naturally detached and were then counted.

Box and whisker plot showing the decrease in isopods in the time after the fish have returned to the reef vs. immediately before. Figure from Sikkel et al 2017.

Box and whisker plot showing the decrease in isopods in the time after the fish have returned to the reef vs. immediately before. Figure from Sikkel et al 2017.

Statistical analysis of the data revealed that grunts which spent the night on the reefs contracted 3 to 44 times as many isopods as those which were left in the seagrass bed. Fish which were placed on the reefs during the 30 minutes before the return time of the wild grunts contained twice as many isopods as those which were exposed to the reef after the return time. Nighttime isopod load on the reefs was also much higher than the daytime load, and isopods were detected on juveniles from the reefs but not the seagrass beds. Overall, these results were significant and suggest that moving to seagrass beds at night is an effective method of isopod evasion for both adult and juvenile grunts, and that the fish return in the morning as isopods become less active. The results from this study suggest that further research is needed into the potential for parasites to drive movements of coral reef organisms.

Works cited
Sikkel, P. C., Welicky, R. L., Artim, J. M., McCammon, A. M., Sellers, J. C., Coile, A. M., & Jenkins, W. G. (2016). Nocturnal migration reduces exposure to micropredation in a coral reef fish. Bulletin of Marine Science.

The imperiled fish fauna in the Nicaragua Canal Zone

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By Nicole Suren, SRC intern

Plans for a new canal through the isthmus of Nicaragua have just been approved by the Nicaraguan government with little to no restrictions on what preexisting waterways can be used as part of this potential new shipping route. The currently proposed route was planned based on economic and technical considerations, but ecological concerns were not factored into the planning, leading to a variety of potential ecological problems due to the construction of the canal. These ecological detriments include overexploitation of the environment, increased water pollution, water flow modification, destruction or degradation of habitat, and the establishment and spread of non-native species. The currently proposed route is of special concern because it not only passes through Lake Nicaragua, a freshwater ecosystem of very high socioeconomic importance, but also because it connects two currently isolated drainage basins, the San Juan drainage basin and the Punta Gorda drainage basin.

Proposed route (solid line) and alternative routes (dashed lines) of the Nicaragua Canal. The 3 drainage basins involved are San Juan (red), Punta Gorda (blue), and Escondido (yellow). Fish-sampling locations are marked with open diamonds. (Härer et al. 2016)

Proposed route (solid line) and alternative routes (dashed lines) of the Nicaragua Canal. The 3 drainage basins involved are San Juan (red), Punta Gorda (blue), and Escondido (yellow). Fish-sampling locations are marked with open diamonds. (Härer et al. 2016)

This study was conducted in order to establish a baseline of biodiversity in the two potentially affected drainage basins, as well as the surrounding basins, so that changes in biodiversity due to the construction of the new canal can be accurately measured and compared against previous levels. The researchers measured biodiversity by taking surveys of the fish in each ecosystem in question with nets, and then sampling two species each from three families of fish that are common in the area. These samples were then used in a DNA analysis, where common sequences of DNA from each species were analyzed for differences. In general, the more similar the DNA sequences, the more closely connected two populations are, and the less similar the DNA sequences, the less closely connected the populations are. Based on the DNA analysis, “populations within the same basin showed almost no genetic differentiation, whereas comparisons across basins exhibited higher differentiation.” This means that populations of fish within the same drainage basin are very similar to each other, while they are quite different from fish in other, unconnected drainage basins. They also found that Punta Gorda and San Juan have 27 species in common, but they also have 24 and 31 species, respectively, that only occur in one basin.

Diagrams showing connectivity between basins (A-C) and within different locations in the San Juan drainage basin (D-F). The sizes of the circles are proportional to the sample sizes, and the proximity of the circles to each other represent how closely connected they are genetically. (Härer et al. 2016)

Diagrams showing connectivity between basins (A-C) and within different locations in the San Juan drainage basin (D-F). The sizes of the circles are proportional to the sample sizes, and the proximity of the circles to each other represent how closely connected they are genetically. (Härer et al. 2016)

Measures of biodiversity are important because they can be a direct indicator of how healthy an ecosystem is. In other words, a diverse ecosystem is a healthy ecosystem. Since the San Juan and Punta Gorda ecosystems contain populations that are so distinct from one another (which is one of the ways biodiversity is defined), the proposed connection between the two is potentially detrimental to the health of those environments because the physical barriers maintaining their diversity would be removed, thereby reducing their diversity and health. Because of these effects, the authors strongly recommend that the precautionary principle be used, and that a more ecologically sound route for the canal be chosen before starting construction.

Works Cited
Andreas Härer, Julián Torres-Dowdall, Axel Meyer. “The Imperiled Fish Fauna in the Nicaragua Canal Zone.” Conservation Biology, vol. 00, no. 0, 2016, pp. 1-10, doi:DOI: 10.1111/cobi.12768

Novel use of epidemiological models to control the spread of unwanted behaviors in marine mammals

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By Cameron Perry, SRC intern

Animal behavior is often learned or passed down through social interactions with other individuals. However, sometimes these socially transmitted behaviors increase exploitation of human resources, which may threaten human safety and economic livelihood (Schakner et al., 2016). Schakner et al. (2016) examined a case study where California sea lions (Zalophus californianus) discovered salmonids that had migrated up the Columbia River to the fish ladders located at the Bonneville Dam. Sea lions began foraging at the dam and increased the mortality of the Columbia River’s salmon and steelhead runs, 13 of which are listed under the Endangered Species Act (Schakner et al., 2016). The mouth of the Columbia River is home to tens of thousands migratory male California sea lions, however, the number of individuals foraging at the Bonneville dam began to sharply increase in 2002. This rapid increase in foraging was attributed to social learning and, in order to protect the endangered salmonids at the Dam, a culling program was established in 2008.

Study area for the case study which shows the Bonneville Dam and the East Mooring Basin where the males aggregate [Schakner et al., 2016]

Study area for the case study which shows the Bonneville Dam and the East Mooring Basin where the males aggregate [Schakner et al., 2016]

Social transmission of behaviors often mimic spread of diseases in a population. Schakner et al. (2016) aimed to use models from disease ecology to estimate the social transmissibility of dam-foraging behavior, explain how social transmission can be modeled similarly to diseases and to finally examine how effective and whether culling was necessary.

A California sea lion (Zalophus californianus) goes for a swim [Wikipedia Commons]

A California sea lion (Zalophus californianus) goes for a swim [Wikipedia Commons]

The benefits of early intervention are well known in infectious disease ecology and the social transmission of dam-foraging behavior in Californian sea lions supported this claim. The results showed that an earlier start to culling would have led to less overall foragers (Schakner et al., 2016). Similarly, if culling started prior to 2005, then fewer individuals would have to be removed than the current numbers. These results together mean that an immediate implementation of a culling program during the 2002 period of sharp increase in foraging behavior could have reduced the negative extent of social transmission and recruitment to the Bonneville Dam (Schakner et al., 2016). This also highlights the need for early culling efforts from a conservation and management aspect to minimize the total number of animals removed.

The authors hope that the Bonneville Dam case study could serve as an example what should be done in similar situations. They provided a novel synthesis of disease ecology models in social transmission and spread of behaviors in wildlife. Animal behaviors can rapidly spread through a population like an infectious disease. Social transmission of behaviors, like infectious diseases, can be managed through early intervention to reduce their spread and reach through a population.

Works cited
Schakner, Zachary A, Michael G Buhnerkempe, Mathew J Tennis, Robert J Stansell, Bjorn K van der Leeuw, James O Lloyd-Smith, and Daniel T Blumstein. 2016. “Epidemiological models to control the spread of information in marine mammals.” Proc. R. Soc. B.

Coral Recruitment Shifts due to Sensitivity to Community Succession

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By Patricia Albano, SRC intern

Environmental disturbances such as natural disasters, anthropogenic effects, and weather pattern changes have a significant impact on ecosystems. Following such disturbances, communities must adapt and rebuild through succession where they evolve to respond to changes. In this study, researchers Christopher Doropoulous, George Roff, Mart-Simone Visser, and Peter Mumby of the University of Queensland studied the positive and negative interactions that impact community succession in the wake of a disturbance and how these interactions differ along environmental gradients.

Figure 1. Soft Corals Found on Palau Reef Caption: These are examples of the soft corals (Nephtheidae) that inhabit reefs in Palau. These corals are important for the structure and function of the reefs. Source: Wikimedia Commons

Figure 1. Soft Corals Found on Palau Reef
These are examples of the soft corals (Nephtheidae) that inhabit reefs in Palau. These corals are important for the structure and function of the reefs.
Source: Wikimedia Commons

Succession in ecosystems usually follows 2 models: facilitation and inhibition (Connel and Slayter 1977). Facilitating organisms “set the stage” for environmental modifications, making the habitat more accommodating for the later-successional species. Inhibiting organisms are early arrivers that reserve space in the habitat for themselves and prevent the invasion of later-successional species (Connel and Slayter 1977). All species interaction includes two components: negative (competition, predation, inhibition) and positive (facilitation) (Paine1980). These two interaction types allowed the researchers to classify the changes they saw in the coral reef ecosystem study sites. This series of experiments investigates how early succession affects coral reef recovery after 2 subsequent typhoons in the island of Palau in the Western Pacific (Figure1) These 2 typhoons (occurring in December 2012 and November 2013) occurred after no typhoon disturbances for over 70 years. This study site was used to explore how the changes in species interactions after a disturbance affect succession in benthic communities with different environmental gradients and how these successional changes affect coral recruitment and recovery after a disturbance (Doropoulos et al. 2016).

The researchers analyzed the eastern barrier reef of the island that had significantly reduced abundances of juvenile corals. Six sites were chosen within to different wave environments: 3 at reefs with lower wave exposure and 3 at reefs with higher wave exposure (Figure 2). Variables accounted for include: grazing potential of herbivorous fish on available grazeable substrate and percent cover of algae groups in the ecosystems.

Figure 2: Six Reefs of the Study Site in Palau Caption: This map indicates where the 6 reefs used in the study are located along the Palau coastline. The pictures indicate differences in coral recruitment between caged (shielded from herbivorous fish) and uncaged (open to grazing) portions of the reef. Source: Doropoulous et al. 2016

Figure 2: Six Reefs of the Study Site in Palau
This map indicates where the 6 reefs used in the study are located along the Palau coastline. The pictures indicate differences in coral recruitment between caged (shielded from herbivorous fish) and uncaged (open to grazing) portions of the reef.
Source: Doropoulous et al. 2016

The researchers found that 3 patterns in environmental drivers influenced the ecosystem. First, a 70% reduction in fish grazing potential was found at the sites that had loss of the majority of live coral cover after the typhoons. Second, shifts in dominance from coral to microalgae occurred at 3 sites with medium wave exposure. Last, microalgae was more abundant in microhabitat crevice areas within both the medium and low wave exposure sites. Coral recruitment was also higher in these crevice areas within the reefs. The researchers came to the conclusion that when herbivorous fish are excluded from reef habitats, a gradual shit towards an algae dominated system occurred at both medium and low wave exposure locations. The results collectively showed that differences in interaction strengths along environmental gradients can lead to changes in the early succession of benthic life that can lead to the inhibition of system recovery after a disturbance such as a typhoon. This experiment revealed important information on how ecosystems recover after disturbances. With this knowledge, nations and conservation organizations can effectively manage their reef ecosystems following a disturbance such as a natural disaster or a weather change. This study also reveals how important it is for healthy reefs to exist in order for ecosystems to continue thriving and support a vast array of life.

Works cited:

Paine, R. T. 1980. Food webs: linkage, interaction strength and community infrastructure. The Journal of Animal Ecology 49: 667-685.

Connell, J. H., and R. O. Slatyer. 1977. Mechanisms of succession in natural communities and their role in community stability and organization. American naturalist:1119- 1144.

FAD’s and Food Security in the Pacific Islands

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By Kevin Reagan, SRC intern

In the countries and territories of the Pacific Islands, the people depend very heavily on fish for food. In Pacific Island countries and territories (PICT’s), 50-90% of the dietary animal protein in coastal communities comes from fish. This is based mostly on small-scale subsistence and commercial fishing for fish mainly associated with coral reefs, as well as some pelagic (open ocean) species (mainly tuna). Consumption of fish here is several times higher than the global average, and tuna is of particular importance and value (Bell et. al 2009).

A map of the Pacific Island region. https://commons.wikimedia.org/wiki/File:Pacific_Culture_Areas.jpg

A map of the Pacific Island region. https://commons.wikimedia.org/wiki/File:Pacific_Culture_Areas.jpg

As human populations grow, the government is encouraged to provide at least 35 kg of fish per person per year, due to the fact the fish is filled with fatty acids, proteins, and vitamins, and the most promising option for food security in the region. The arable, farmable land is scarce, which makes the level of subsistence provided from small farms scarce as well. It is also a better alternative to nutrient-poor imported foods that are beginning to be consumed in the region and can combat the occurrence of non-communicable diseases in the region (Bell et al. 2015).

The main issue currently is that coral reef fish populations cannot keep up with the growing demand for food, and will not yield the necessary 35 kg/person as the population continues to grow. Bell et. al (2015) propose that PICT’s allocate more of the tuna they catch to local food security, and make fish-aggregating devices (FAD’s) a priority. By 2035, it is estimate that tuna with need to account for 25% of the fish required for food security in the region (Bell et al. 2015).

A yellowfin tuna, the most common species of tuna caught in the Pacific Islands. https://commons.wikimedia.org/wiki/File:Al_mcglashan_tuna.jpg

A yellowfin tuna, the most common species of tuna caught in the Pacific Islands. https://commons.wikimedia.org/wiki/File:Al_mcglashan_tuna.jpg

FAD’s are though to be “one of the most practical vehicles for improving local fish access” in PICT’s (Bell et. al 2015), and are installed nearshore in depths of 300-700 meters. Pelagic fish tend to aggregate at and around floating objects for several days, and therefore FAD’s improve access to these fish. They have been shown to improve supply and consumption in rural areas, and cost-benefit analyses of FAD’s show the value of tuna and other pelagic fish exceeds the cost of the FAD by 3-7 times. The catch per unit effort tends to be higher, the average fuel consumption by the fisherman lower, and the returns on investment are anywhere form 80-180%. Preliminary studies in Micronesia and Vanuata indicate that FAD’s can alleviate fishing pressure on coral reef communities as much as 75% by transferring some of the fishing to oceanic fisheries, i.e. pelagic fish (Bell et al. 2015).

Though FAD’s have many benefits, extensive planning, monitoring, and research will be required for them all to be seen. An important aspect of this is participation and a sense of ownership by the local communities; some FAD’s have been sabotaged and vandalized in the past. Investments will need to be made, and are described in detail in the paper (Bell et al. 2015).

A fish-aggregating device (FAD) with mahi mahi schooling underneath. https://www.flickr.com/photos/landlearnnsw/3017619031

A fish-aggregating device (FAD) with mahi mahi schooling underneath. https://www.flickr.com/photos/landlearnnsw/3017619031

The first necessary investment is to identify priority locations for nearshore FAD’s. This is especially important in rural communities but is also important for urban communities. The community then needs to be engaged so that they can realize the full potential of FAD’s and none will be lost due to vandalism. The effectiveness of exclusion zones for industrial fleets must also be assisted; there are concerns that industrial fleets fishing near the boundaries of exclusion zones affect the number of fish that are then contained within the zone. Next, catches around nearshore FAD’s needs to be monitored and the level of improvement of coral reef management initiatives from FAD’s should be evaluated. Finally, the design and placement of the FAD’s must be improved (Bell et al. 2015).

FAD’s provide path to increase tuna and other pelagic fish availability to rural and urban comm. in Pacific Islands. They are a practical way to allow countries to get the small share of the region’s tuna catch they need to have food security, and are also a positive adaptation to climate change and population growth. Exclusion zone expansion needs to be considered as well if it is shown that industrial fleets are catching tuna marked in the exclusion zone (Bell et al. 2015).

Investments need to be made in FADs as part of food security in PICTs. Current FAD numbers not enough, and infrastructure needs to be maintained post-installation. Damaged FAD’s need to be replaced as soon as possible or momentum will be lost in the community. To do this, communities need large stockpiles of spare parts and access to the vessels and personnel necessary to install new FADs. However, current budgets are not large enough. National governments also need to be committed to and have ownership of FAD programs, and potentially use funds from license revenues from distant fishing nations that use their waters (Bell et al. 2015).

Local governments can also enlist the help of industrial fishing companies that currently deploy anchored FAD’s when fishing to assist in the installations of nearshore FAD’s. Each FAD program within PICT’s needs to be adapted to fit the capabilities of each particular island- the points outlined in paper are a blueprint, not a checklist. Overall, FAD’s are one of the few options that can provide food security, especially in rural coastal areas, and should be seriously considered in the coming years (Bell et al. 2015).

Works Cited

Bell, Johann D., et al. “Optimising the use of nearshore fish aggregating devices for food security in the Pacific Islands.” Marine Policy 56 (2015): 98-105.

Bell, Johann D., et al. “Planning the use of fish for food security in the Pacific.” Marine Policy 33.1 (2009): 64-76.

Cleaner fishes and shrimp diversity and a re-evaluation of cleaning symbioses

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By Shannon Moorhead, SRC Masters Student

If you’ve ever gone diving on a tropical coral reef, you may have noticed some of the fish seemed to be behaving rather strangely: a solitary fish hovering just above the reef while smaller fish pick at its skin and mouth. While this may appear bizarre compared to the other creatures zipping about the reef, this is a common behavior in the animal kingdom known as cleaning symbiosis. Cleaning symbiosis occurs when, after brief communication between the animals involved, a cleaner animal removes harmful materials from a client animal of a different species. This is a mutually beneficial act for both the cleaner and the client: the client is ridded of parasites and dead skin while the cleaner gets an easy meal! 

A pair of Hawaiian cleaner wrasse clean a dragon wrasse. [Source: Wikimedia Commons, photo by Brocken Inaglory (https://commons.wikimedia.org/wiki/File:Cleaning_station_konan.jpg)]

A pair of Hawaiian cleaner wrasse clean a dragon wrasse. [Source: Wikimedia Commons, photo by Brocken Inaglory (https://commons.wikimedia.org/wiki/File:Cleaning_station_konan.jpg)]

Many water-dwelling organisms have been observed cleaning others. Currently, researchers estimate there are about 208 species of marine and freshwater cleaner fish and 51 species of marine cleaner shrimp known to the scientific community. Some of these species are considered “dedicated cleaners”; for these fish and shrimp, cleaning is a major aspect of their lifestyle once they grow past the larval stage. Other, less committed cleaners, are designated as “facultative cleaners”. There are various levels of facultative cleaning. Some facultative cleaners are opportunistic, only partaking in cleaning when the opportunity presents itself. Others may be temporary, acting as cleaners during only a portion of their life cycle.

Interspecific communication between cleaner and client is a key aspect of cleaning symbiosis. Acts of assertion or submission, by client or cleaner or both, are the catalysts that initiate the cleaning process. Often, cleaners will perform a “dance” or touch the client to signal their intention to clean; the willing client then submits and poses itself in a way that indicates its acceptance of the cleaning. While visual cues are important to this process, in some cases tactile stimulation is just as, if not more important. By approaching and touching the client, cleaner fish make it clear that they are not prey items, as prey would not directly approach a potential predator. Cleaning interactions between cleaner shrimp and moray eels, who have poor vision and are primarily nocturnal, are most likely initiated solely by tactile stimulation. Shrimp have been observed touching eels with their antennae and legs, followed by morays submitting and opening their mouth, allowing the shrimp to begin cleaning.

A shrimp cleans inside the mouth of a moray eel.[Source: Wikimedia Commons, photo by Steve Childs (https://commons.wikimedia.org/wiki/File:Moray_Eel_and_Cleaner_Shrimp.jpg)]

A shrimp cleans inside the mouth of a moray eel.[Source: Wikimedia Commons, photo by Steve Childs (https://commons.wikimedia.org/wiki/File:Moray_Eel_and_Cleaner_Shrimp.jpg)]

Though the cleaning relationship is usually mutually beneficial, sometimes the cleaner or client may take advantage of the other’s trust, referred to as “cheating”. Cheating occurs when the symbiotic relationship is disturbed by one of the partakers. For example, clients have been known to eat their cleaners and cleaners have been reported choosing to eat the mucus or healthy scales of their client fish instead of ectoparasites or dead or diseased tissue. Despite the threat this breach of contract poses to the health of cheated participants, it does not occur often enough to outweigh the benefits of cleaning symbiosis.

Though it is well known that the removal of ectoparasites is beneficial for the health of fishes, the ecological balance maintained by cleaner organisms is poorly understood. Many studies have attempted to quantify loss of reef fish abundance and diversity after the removal of one or multiple species of cleaners from a reef, with varying results. Some studies reported little change in the number of fish, while others reported drastic differences in the number and diversity of fish observed, as well as increases in the number of lesions on remaining fish. The large diversity and abundance of cleaners in marine ecosystems suggest they perform a critical ecological function; the discrepancies among study results make it clear that more research must be done to fully understand the intricacies and significance of cleaning symbiosis.

Works cited

Vaughn DB, Grutter AS, Costello MJ, Hutson KS (2016). Cleaner fishes and shrimp diversity and a re-evaluation of cleaning symbiosis. Fish and Fisheries: 1-19. Doi: 10.1111/faf.12198

 

Bait worms: a valuable and important fishery with implications for fisheries and conservation management

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By Brenna Bales, SRC intern

Historically, bait fisheries around the world have been perceived as low-value, and their often limited, local extent makes large-scale management and conservation policy difficult to implement. Watson et. al 2016 explored three ragworm fisheries in the United Kingdom to investigate these claims, based on both evidence gathered scientifically and from an analysis of published literature. The data on polychaete bait fisheries is extremely limited, causing inaccurate estimates of catch amounts and collection efforts. In order to accurately assess the three bait fisheries of focus and other fisheries worldwide, Watson and other researchers assessed the following: retail value of bait species collected, extent of collection efforts both geographically and quantitatively, bait storage methods, and the choice and amount of bait used by angler fisherman on an average fishing trip.

The five most expensive (£/kg) species of marine animals sold on the global fish market are polychaetes (Glycera dibranciata, Diopatra aciculata, Nereis (Alitta) virens, Arenicola defodiens, and Marphysa sanguinea). The values of these bait species were quantified using retail prices of the species online and from data gathered from other literature sources. It was concluded that N. virens landings alone in the UK annually are worth approximately £52 million. Globally, this number is around £5.8 billion, with 121,000 tonnes of N. virens being landed worldwide. This demonstrates the high value of polychaete bait, contrary to popular opinion.

Nereis (Alitta) virens, commonly known as a sand worm, are a popular polychaete worm collected for bait purposes in UK tidal fisheries. (source: https://commons.wikimedia.org/wiki/File%3ANereis_virens_und_Nereis_diversicolor.jpg)

Nereis (Alitta) virens, commonly known as a sand worm, are a popular polychaete worm collected for bait purposes in UK tidal fisheries. (source: https://commons.wikimedia.org/wiki/File%3ANereis_virens_und_Nereis_diversicolor.jpg)

The three UK sites surveyed were Fareham Creek, Portsmouth Harbour; Dell Quay, Chichester Harbour; and Pagham Harbour. They were monitored over a period from August to September 2011, using remote closed circuit television recordings. The time for each digger on-site was recorded, and based on the number of times they placed a worm in their collection bucket, the biomass (mass of live worms) collected was estimated. The mean removal rate per bait collector per hour was 228 ± 64 worms. This large amount of collection can lead to things like environmental disturbance (trampling), over-exploitation of collection species, and the depletion of food resources for bird species that consume these worms.

This Japanese coastal bird feeds off a small ragworm, species that are globally collected as bait. When too many worms are removed by collectors, it can have serious consequences for the animals that rely on them for food. (source: https://commons.wikimedia.org/wiki/File%3ACharadrius_mongolus_stegmanni_eating_ragworm.JPG)

This Japanese coastal bird feeds off a small ragworm, species that are globally collected as bait. When too many worms are removed by collectors, it can have serious consequences for the animals that rely on them for food. (source: https://commons.wikimedia.org/wiki/File%3ACharadrius_mongolus_stegmanni_eating_ragworm.JPG)

An investigation as to how long certain species could be kept fresh before being used as bait on fishing trips was also conducted. The amount of time that N. virens could be maintained as viable bait was at the least 2 weeks. Given the average amount of N. virens used on angling trips per week was 0.33 kilograms, that amount of bait could be collected in only 28 minutes during a tidal cycle, based on the mean removal rate per bait collector per hour.

In conclusion, Watson et. al. proved that there needs to be a re-examination of the importance of polychaete bait fisheries worldwide, in order for better conservation initiatives to be launched. Seeing as the majority of these bait fisheries are located in MPAs (marine protected areas), better regulations must be enforced. There are several proposals in the study, such as personal catch limits, surveillance conservation, and stakeholder involvement. Overall, these fisheries are worth a lot more than is currently thought, and the implications of continuing poor management could have serious consequences.

Works Cited

Watson, Gordon J., et al. “Bait worms: a valuable and important fishery with implications for fisheries and conservation management.” Fish and Fisheries (2016).

A novel aspect of goby–shrimp symbiosis: gobies provide droppings in their burrows as vital food for their partner shrimps

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By SRC intern, Andriana Fragola

The goby A. japonica and shrimp A. bellulus symbiosis are a perfect example of a mutualistic relationship between two marine animals. The goby lives in the shrimp’s burrow, which lends it shelter, and the goby warns the shrimp if there is a predatory threat nearby (Kohda et al. 2017). It has been hypothesized that the shrimp actually eats the goby’s droppings as its primary food source (Kohda et al. 2017). Kohda and colleagues conducted a laboratory experiment to replicate this relationship, and examine if this feeding behavior is actually occurring.

Figure1 

Field studies were conducted to examine the goby and shrimp interactive behavior. Between the shrimps, A. bellulus and the gobies A. japonica it was observed that the shrimps were not foraging much outside of their burrow, and the gobies were never really observed defecating outside of their burrow (Kohda et al. 2017). Most burrowing organisms do not defecate inside of their burrows – likely to be an act to keep it cleaner (Kohda et al. 2017). If the shrimp is using the goby’s droppings as a nutritional supplementation, then it would not be an issue of keeping the burrow clean because the droppings would still be removed via consumption by the shrimp (Kohda et al. 2017). The animals were collected at Morote Beach, Ehime Prefecture, Japan and were then studied in a laboratory setting.

The gobies and shrimps were kept in tanks with the burrow being a vinyl tube with one open side up against the glass wall of the tank for visual observation (Kohda et al. 2017). This experiment took place over a 2 week period. The shrimp were weighed prior to and after the experiment to determine if they had lost weight when they had no access to food other than the goby droppings (Kohda et al. 2017). In treatment 1, in order to make the goby feed inaccessible to the shrimp, it was placed on a suspended board away from the entrances of the burrows (Kohda et al. 2017). This way the goby could reach the food by swimming, but the shrimp could not and had to rely entirely on the goby droppings for nutrition. In treatment 2, the gobies and shrimp were kept in different tanks, and the researchers collected the goby faeces and then placed them up at the top of the shrimp’s burrow (Kohda et al. 2017). The shrimps were noted to come to the entrance and collect the faeces and bring them back down into the burrow and eat them (Kohda et al. 2017). A control tank was set up where the shrimp were isolated from the gobies, and were not fed during the entirety of the experiment (Kohda et al. 2017).

Final observations noted that the gobies stayed very close to the burrow unless they were feeding, and were never observed defecating outside of the burrow (Kohda et al. 2017). The shrimp were never noted to forage outside of the burrow unless they were taking algae off of the rocks near the burrow entrance (Kohda et al. 2017). Between the two treatments, there was not a significant difference between body weight of shrimps prior and after the experiment (Kohda et al. 2017). But there was a significant decrease in shrimp body weight in the control groups where they were isolated from the gobies (Kohda et al. 2017). Meaning that the shrimp were able to maintain a stable body weight with only the goby faeces as food (Kohda et al. 2017).

 

Figure2
Understanding behavioral relationships between species is incredibly important for conservation initiatives. Learning that two species heavily rely on each other to thrive is vital in establishing protection for them. In a mutualistic relationship similar to this, both species need to be protected because if one is missing, they cannot perform their usual behaviors, and do not have that resources they typically rely on. For example, the droppings of the goby being a primary food source by the shrimp. This study demonstrated that solely having goby droppings as food is enough to maintain the shrimp’s weight even without other nutritional sources available (Kohda et al. 2017). Therefore the goby is a very beneficial to the shrimp as a partner, and without these mutualistic relationship the shrimp would have a much more limited food supply, and the goby would not have a burrow to reside in.

Works cited
Kohda, M., Yamanouchi, H., Hirata, T., Satoh, S., & Ota, K. (2017). A novel aspect of goby–shrimp symbiosis: gobies provide droppings in their burrows as vital food for their partner shrimps. Marine Biology, 164(1). doi:10.1007/s00227-016-3060-2

Use of local ecological knowledge to investigate endangered baleen whale recovery in the Falkland Islands

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By SRC intern, Molly Rickles

In this study, Frans and Auge looked at baleen whale population in the Falkland Islands in the post-whaling era. Due to whaling in the early 1900s, whale populations here have decreased dramatically, but recent observations suggest that their numbers are currently increasing. However, there is a lack of population data, making this study critical.

Methods

The main goal of the research was to understand how well the baleen whale population is doing post-whaling in the Falkland Islands. To do this, the scientists used LEK, or local ecological knowledge. In this method, interviews were conducted with local Falkland residents to determine how often whales are sighted off the coast. The residents were asked to draw pictures on a map of where they saw the whales. Each interview was given a reliability rating based on how confident and detailed the account was. This data was used to supplement the existing International Whaling Committee data from the whaling era. With the combined data, the researchers aimed to look at when the whale sightings were most common and to determine the most common places where the whales were seen.

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Results

Over the course of the study, 3,842 whale sightings were recorded and Falkland residents recorded 631 of those observations. Since LEK is not always a reliable method, it was determined that about 70% of the observations recorded using LEK were reliable, and could be used in the study. It was found that in the 1970’s, no whale sightings were recorded because it was right after the whaling era. By the early 2000’s, the number of whale sightings increased 11-fold, showing a population recovery. Out of all of the baleen whale species, sei whales (Balaenoptera borealis) showed the largest increase since the whaling era, and are currently the most abundant whale species in the Falkland Islands. It was also determined that baleen whales are most common during the summer and fall months, based on recorded sightings.

Outcomes

This study was an important step in understanding baleen whale populations and how they have recovered since the whaling era. Using LEK allowed the scientists to get population data even when there was a lack of empirical data, which is a new technique that hasn’t been used regularly in other studies. This new technique allowed the researchers to determine baleen whale populations in the Falkland Islands, which can be used as a reference for the future of whale conservation. This is especially critical now because of the increasing threats to whales, such as increasing economic development in the Falkland Islands. Since the whales have recovered from the whaling era, it is now important to keep the population healthy, and this study provides an important monitoring tool for future conservation efforts.

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References

Frans, V.F., & Auge, A. A. (2016). Use of local ecological knowledge to investigate endangered baleen whale recovery in the Falkland Islands. Biological Conservation, 202, 127-137. dio: 10.1016/j.biocon.2016.08.017