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Sustainable Fisheries

Queen conch "graveyard" study taking place at CEI

An adult conch in the shallow water High on top of the Bahamian crest is a queen conch—an iconic representation of how truly integrated marine ecosystems are to Caribbean culture. Queen conch (Strombus gigas) is a large gastropod native to the Caribbean and has been a staple in the Bahamian diet for centuries.   Unfortunately, the overfishing of conch has caused massive declines in populations, and conservation efforts are greatly needed to promote a healthy and sustainable conch fishery in the Bahamas.

Selecting conch at random to  be used in a trial

In fisherman lore around the Bahamas it is said to be bad luck to throw knocked conch into the water, as it will scare away living conch—thus, huge conch middens are often found onshore. But, some conch are still tossed overboard at sea, and it is thought this may also be affecting conch populations. The Sustainable Fisheries team, here at the Cape Eleuthera Institute (CEI), is testing avoidance behavior from conch with help of several Island School students. The main question is- do conch flee upon seeing/smelling an injured or dead conspecific, and if so, what sort of cue is triggering movement?

Sustainable Fisheries intern Cara measures the distance moved by a conch in a behavioral trial

So far 40 trials have been conducted, and CEI’s Claire Thomas, Program Manager for Sustainable Fisheries, will be presenting the preliminary results at the Bahamas National Trust Natural History Conference in Nassau this week. As we conduct more trials and gain more insight into potential conch avoidance behavior, there may be implications for new management strategies to better protect this important species—stay tuned for results!

Nassau grouper spawning aggregation expedition

Nassau grouper is an economically important species in The Bahamas. Due to heavy fishing pressure, there have been marked decreases in their population sizes, especially noticeable during their spawning season. The spawning season takes place during the winter months, from December to the end of February, and the aggregations occur during the full moon. Dr. Kristine Stump from the Shedd Aquarium has been monitoring Nassau grouper in The Bahamas to track their movements to spawning aggregations, as well as to quantify the number of Nassau grouper at these historical spawning sites. The researchers that took part in the Nassau grouper work in front of the Shedd Aquarium vessel

This January, the Shedd Aquarium research vessel, The Coral Reef II, travelled to Long Island, to historical spawning sites, with a representative of The Cape Eleuthera Institute on board, to assist Dr. Stump with her research. Throughout the week-long journey, the researchers on board performed dive surveys to quantify spawning stock size at one specific site.  Unfortunately, very few Nassau grouper were aggregating at the site during the times of the surveys; at most 20 were noted on one survey. Illegal fishing was occurring at the time the vessel reached the site, which could explain the decreased abundance of the grouper. Poor weather conditions prevented the researchers from performing surveys on the night of the full moon, so it is unclear if numbers increased during the spawning event. 

Throughout the trip, amidst the dive surveys, Nassau grouper were  implanted with transmitters. These transmitters track the movements of the Nassau grouper from the spawning sites back to their original habitat with strategically placed receivers, in efforts to understand where they come from and how far these fish travel to these spawning sites. At the spawning site, the five receivers were extracted and replaced with new receivers. The data from the receivers showed the movements of the Nassau grouper which will add to Dr. Stump's dataset. Blood samples were also collected from these fish for Krista Sherman from Exeter University, who is using this blood to look at hormone levels and ways of determining sex of grouper non-invasively.

Although the weather failed to cooperate, four fish were implanted with transmitters which will help provide data for the upcoming spawning period, and the receivers have provided Shedd Aquarium with useful data.

 

CEI Research Team presents at conference in Abaco

Last week, researchers from The Cape Eleuthera Institute traveled to Abaco for the 7th Biennial Abaco Science Alliance Conference (ASAC) hosted by Friends of the Environment. Over the course of two days, posters and presentations alike highlighted research findings in natural history and environmental science in The Bahamas. Drawing a diverse audience with scientists from The Bahamas to as far as Canada, local community members and high school students from Abaco, the conference provided a forum for sharing scientific knowledge on the diverse ecosystems of The Bahamas. Dr. Owen O'Shea presenting at the conference.

 

Dr. Owen O’Shea, Research Associate for the Shark Research and Conservation Program, gave an engaging presentation on the ongoing stingray research project at CEI and ecosystem-driven approaches to conservation. Candice Brittain, Applied Scientific Research Department Head, spoke about the recent assessment of the queen conch nursery ground in South Eleuthera. Her presentation was followed by a workshop on conservation of queen conch in The Bahamas, led by the Bahamas National Trust. Georgie Burruss, Research Assistant for the Flats Ecology and Conservation Program, presented new findings on marine debris in the Exuma Sound and plastic ingestion by pelagic sportfish. She also gave a talk on studies conducted by the Flats Program that have aided in developing the Best Handling Practices for bonefish and protection of critical bonefish habitat. Finally, Eric Schneider, graduate student at University of Illinois Urbana-Champaign, presented research he conducted at CEI on temperature change effects on juvenile and adult schoolmaster snapper.

ASAC provided a unique opportunity for networking between the local community, students, and researchers for sharing knowledge on ecosystems across The Bahamas. Researchers from CEI look forward to attending ASAC in 2018!

Conch nursery project update

This semester, the Sustainable Fisheries Team has been surveying the waters of South Eleuthera in search of juvenile queen conch. In 1993, South Eleuthera had the largest surveyed juvenile conch nursery in The Bahamas.  An aggregation of juvenile queen conch piled on top of each other in South Eleuthera

 

On the seashores of The Bahamas, it is common to see conch middens, or large piles of discarded conch shells. When fishermen return from their fishing trips, they take the fleshy meat from inside the shell and then throw that shell away. Recent conch shell midden data shows a significant increase in the harvest of juveniles. In South Eleuthera, 49.2% of the conch shells in one local midden are characterized as juveniles (lack of a flared lip).There has also been a significant decline in the number of adult conch mating aggregations in South Eleuthera.

Understanding if there is still an important juvenile conch nursery in South Eleuthera will help determine the current status of this economically and ecologically important species. Using methods created by researchers at the Shedd Aquarium, snorkelers are towed behind a boat on a manta-tow board with a Gopro attached. Images are taken continuously to document the number of conch, life stage and habitat type throughout the tow. The images are then pieced together to create a visual map of the tow. This methodology allows a rapid, accurate assessment of conch, and also documents the habitat types conch are being found in. The depths and temperature are also recorded for each tow.

During many of the surveys,  only a small number of queen conch were observed, and in some tows no conch were found. But, recently, a high density of juvenile queen conch was discovered. These findings could help inform future sustainable harvesting strategies and conservation management for queen conch.

Our partner, the Shedd Aquarium, have a research team that is currently conducting further research to investigate the dispersal of conch eggs throughout the oceans currents. This further research is vital for understanding the full life cycle of queen conch and the locations of important habitats for this species.

We recommend that you only harvest conch with a fully flared lip with at least a 15mm thickness. This is when conch is considered sexually mature and can reproduce. It is important that species are able to reproduce before they are harvested, otherwise populations will most likely crash and possibly become endangered or even extinct.

A busy week with The Island School Research Symposium and Parent's Week

Last Thursday was The Island School Research Symposium! It is a highlight of Parent's Week, and a time for parents to hear about the good work being done by their sons and daughters. Throughout the semester, The Island School students have collaborated with CEI researchers, contributing to ongoing research projects. They have been studying various ecosystems around Eleuthera, including inland ponds, the pelagic zone, the deep sea, shallow water sandbars, and tidal creeks . Dr. Craig Dahlgren discussing the current state of coral reefs in The Bahamas.

 

In all, nine projects were presented, and Dr. Craig Dahlgren, Senior Research Scientist for the Bahamas National Trust, concluded the event with a talk on the state of coral reefs in The Bahamas. All nine projects are being featured on our Instagram (@CEIBahamas) and Facebook pages, so please check them out for more details on the amazing research done this semester!