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Master's Candidate- California State Northridge
Master's Scholarship Recipient, 2018
Afraid to reproduce? Measuring fish reproduction in risky environments
I have spent the past two summers studying the reproductive behavior of bluebanded gobies, Lythrypnus dalli. This species is highly abundant at Santa Catalina Island, CA, and female gobies reproduce by laying nests of eggs, which has allowed me to directly examine their reproductive responses to environmental conditions. Bluebanded gobies are constantly threatened by a suite of natural predators, particularly the kelp bass, Paralabrax clathratus, and it has been shown that gobies alter their behavior in response to this piscivore. My research aims to assess the short and long-term effects of risk on bluebanded goby reproduction through a series of caging experiments. This work has the potential to improve our understanding of how sublethal effects of predators, which are often overshadowed by lethal effects alone, may shape prey communities and behavior.
To test the effects of predators on reproduction in bluebanded gobies, I ran a manipulative experiment in Big Fisherman Cove, a marine reserve at USC’s Wrigley Marine Science Center (WMSC). I constructed a series of subtidal rocky reefs, stocked them with populations of 20 bluebanded gobies, and covered them with one of three cage types to simulate risk levels perceived by the gobies: large exclusion cages (low-risk environment), small exclusion cages (medium-risk environment), and small cages with side panels removed to allow for predators to move freely on and off the reefs (high-risk environment). I also stocked each reef with artificial nests (short PVC tubed lined with acetate), where female gobies laid eggs to later be fertilized and guarded by males. I performed SCUBA surveys twice a week for one month, during which I checked each nest for eggs and photographed the nests when eggs were present. I uploaded those nest photos to my computer and counted the eggs to compare reproductive output among the three treatments.
Though my analyses are ongoing, I’ve found that gobies lay the same amount of eggs on each reef, regardless of risk level, and that this pattern persists over time. These results are consistent with our behavioral observations, where gobies exhibited similar risk response behaviors for exposure times and foraging rates, even when subjected to different risk levels. Interestingly, egg production varied over time, with maximum output mirroring the natural reproductive cycle for this species. These findings posit that predation risk is having less of an impact on prey populations than has been suggested in other marine systems, at least in this species of reef fish. As mentioned previously, this study was conducted in a marine reserve, where predators reach high, natural abundances not achieved in unprotected areas. As such, we may have seen a different result had this study taken place outside of the reserve, where predator presence, both lethal and sublethal, has been altered by anthropogenic activities.
The AAUS scholarship has benefitted my thesis project immensely. Without this financial support, I would not have had the opportunity to gain invaluable field research, mentorship, and outreach experience at Catalina Island. Having the means to conduct research remotely allowed me to interact and foster professional relationships with top scientists and public stakeholders. I am grateful for AAUS and its continued support of graduate research. Thank you to all the fantastic volunteer divers and undergraduate researchers that have helped me carry out this project, and to my faculty mentors for their time and support during my thesis work. After my Master’s I hope to pursue more studies involving fitness responses and life history strategies of marine critters in a PhD program.
Lastly, if you are an undergraduate or graduate student interested in conducting field research at WMSC, check out their fellowship opportunities at this link: https://dornsife.usc.edu/wrigley/wrigleysummerfellowship/
Biological Science Master’s Candidate-Cal Poly, San Luis Obispo
Master's Scholarship Recipient, 2016
“Crunch... crunch... crunch.” I will never forget the first time I heard the unforgettable sound of a parrotfish grazing on coral reefs. Nearly two years after hearing that sound for the first time, I, along with my research team and hundreds of pounds of scientific dive equipment, headed from California to the Caribbean. The island of St. Croix, part of the U.S. Virgin Islands, was our destination; our mission: to get to know these charismatic parrotfishes on a more personal level. Our focus was to study the feeding behavior of the resident parrotfish species, who are important herbivores in coral reef systems.
Herbivory on coral reefs is a recent focus of research, as herbivores often consume algae in a way that is beneficial to the growth and recovery of live coral. Parrotfishes are an abundant herbivore on coral reefs and provide a plethora of positive impacts, particularly by consuming a significant amount of algae on the reefs. Interestingly, each parrotfish species, which come in an assortment of colors from stunning greens and blues (Image 1) to rainbow sherbet (Image 2), plays a unique role in their community. For example, the Queen parrotfish, Scarus vetula eats mostly small turf algae on complex reef structure, while the Yellowtail parrotfish, Sparisoma rubripinne prefers a bushy, brown macroalgae on a range of substrate types. Our current knowledge of parrotfish behavior comes from studies conducted in locations that have an abundance of each key parrotfish species. However, in some locations such as St. Croix, these fishes are an important source of nutrition, income and cultural value to the local fishing community and are thus subject to high fishing pressure and species loss.
My project as a California Polytechnic State University Master’s student in the Ruttenberg lab, supported by the Kevin Gurr Scholarship, was to determine whether fishing pressure and subsequent species loss has had an effect on parrotfish feeding behavior, and ultimately their positive impact on the coral reefs. We gathered feeding behavior data by using SCUBA and followed individual parrotfishes of each species for 20 minutes at three sites around the island (Image 3). During this time we recorded data such as what food each fish ate and how many bites it took, all while towing a surface float with a GPS unit to track how far the fish traveled (Image 4). A highlight of this study was to be able to dive the beautiful Buck Island Reef National Monument (Image 5). I was prepared for this challenging data collection technique thanks to my rigorous AAUS scientific diving training through the University of North Carolina Chapel Hill and experience as a dive technician prior to my graduate studies.
Although research is still ongoing, my data so far has shown that, broadly, parrotfish species in St. Croix play similar roles to the same species in other Caribbean locations. At a higher-resolution, we do see fine-scale differences in feeding behavior, but we are still working to determine if fishing pressure, species loss, or other environmental variables caused such differences. We also found that three key parrotfish species typically found throughout the Caribbean were absent from the reefs on St. Croix. Similar to the dysfunction and loss of productivity if a restaurant were to lose entire positions such as cooks, servers, and receptionists, this absence indicates the loss of important roles from these St. Croix reefs and potential decline in reef condition if these roles remain unfilled
The Kevin Gurr scholarship not only provided me the means to conduct a dive-intensive field season in the Caribbean to answer important ecological questions, but also gave me the opportunity to develop important relationships with members of the St. Croix fishing community, National Park Service and the University of the Virgin Islands. Over the course of three seasons in St. Croix, I developed relationships of trust and respect with local fishermen who granted me rare access in personal interviews to the family traditions and food-dependence associated with parrotfish and other species. Through conversations with these individuals, I learned the importance of incorporating both cultural and ecological value into metrics for fisheries management in collaboration with local residents. I hope to maintain the relationships that I made through this project and continue to promote discussions between the fishing community, scientists, and policymakers on how to manage the parrotfish fishery in St. Croix in a way that will result in measurable success for all stakeholders.
So, the next time you have the opportunity to snorkel or dive on a coral reef, take the time to listen for that unmistakable “crunch,” and observe the parrotfishes that are crucial to maintain the health of our beautiful coral reefs. You never know what interesting behavior you might witness!
Thank you AAUS for awarding me the Kevin Gurr scholarship and the opportunities that came from it.
Texas A&M University Galveston
PhD Scholarship Recipient, 2016
Jacque Cresswell is a PhD candidate in the Marine Biology Program at Texas A&M University’s Galveston campus. The AAUS Kathy Johnston Scholarship helped support her research on the benthic ecology of Bermuda’s underwater caves. Her main objectives are to complete a modern ecological analysis of benthic foraminifera and to investigate environmental change and primary succession of benthic foraminifera in the Palm Cave System in Bermuda. Specifically, she is exploring the impact of Holocene sea-level rise on the benthic environment in the Palm Cave System. Jacque is comparing microfossil data collected from surface sediment samples to cave sediment cores to analyze the changes in diversity and abundance of benthic foraminifera over time. Benthic foraminifera are single-celled protists that secrete a calcium carbonate shell which remains in the sediment long after the organism has died. Their fossil remains are widely used to reconstruct environmental change in the marine realm and also show excellent promise as environmental indicators for underwater caves.
The underwater caves of Bermuda have limited dry access. Therefore, SCUBA diving played a critical role in the execution of this research. Over a seven-day sampling trip, advanced cave diving techniques were used to collect 50 surface sediment samples, ten sediment cores, and hydrographic data (i.e., pH, salinity, dissolved oxygen, and temperature) from the Palm Cave System. Samples were then taken to Texas A&M University’s Galveston campus, where they are currently being processed and analyzed. Additional SCUBA diving will be necessary to collect more sediment samples. Such an extensive sample collection has greatly increased the impact of Jacque’s research and would not have been possible without the support of the Kathy Johnston Scholarship.