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Length at Maturity Trends for Fishery Species in the Caribbean Region, highlighting Lane Snapper (Lutjanus synagris) in Trinidad

by Mr. Gianluc Robinson 

Overfishing and poor fisheries management may lead to the altering of a fish's life history. Species may sometimes evolve to mature at smaller sizes in response to fishing pressure. This may have deleterious effects on the sustainability of fish populations as bigger individuals contribute higher quantity and quality eggs or sperm toward recruitment. Smaller mature fish may also be more susceptible to changes in environmental conditions and more disadvantaged when competing for resources. The Caribbean and surrounding territories may not have well documented information on length at maturity data for commercially important species to guide fisheries management plans. This study will examine the availability of data in the Caribbean to explore the concept of fishing pressure reducing lengths at maturity.

Fishing regulations throughout the region will also be examined as it relates to minimum catch size limits. It is expected that limited information will be found and that management of these species may be inadequate. Over time, increasing fishing pressure is expected to decrease a population's mean size at sexual maturity (L50) and the size at which all individuals in the population are mature (L100). To further explore this concept, the lane snapper (Lutjanus synagris) was chosen for a case study due to its commercial importance and the availability of previous research on their length at maturity done in 1987 (Manickchand-Dass, 1987).

It is predicted that the L50 and L100 for this study will remain lower than that of past studies (Manickchand-Dass, 1987). Data collection will continue primarily at Tunapuna Fish Market, Trinidad. Total length (TL) will be measured to the nearest millimeter, fish will be weighed to the nearest gram (g) and gonads will be observed macroscopically using an 8-stage model. Additional graphs will be included for further analysis of the data including for length-frequency distribution and frequency of gonad maturity stages within each month.

This study seeks to identify the gaps in data throughout the Caribbean, establish if there is evidence of decreasing lengths at maturity and explore this concept in detail using the lane snapper in Trinidad. The results will suggest a minimum catch size limit for the lane snapper in Trinidad and likely highlight the lack of data on this topic throughout the Caribbean.

Mr. GIANLUC MIKAI ROBINSON is currently an On-the-Job Trainee at The University of Trinidad and Tobago (UTT) working as a Research Assistant in the Geographic Information Systems Unit at the Centre for Marine and Ocean Sciences. He graduated with a Bachelor of Applied Science (B.A.Sc.) in Coast and Ocean Science from UTT in 2018. During his time as an undergraduate student, Gianluc received extensive training and knowledge in the marine environment on various species from highly qualified professors and now current committee members including external advisor, Professor Mark H. Tupper and supervisor, Dr. Kelly Kingon. Gianluc was also the recipient of a sports scholarship for lawn tennis which allowed him to represent UTT in local tournaments.

Gianluc's research is focused on the potential for declining lengths at sexual maturity of marine species throughout the Caribbean region in response to fishing pressure, using the lane snapper as a case study. This dissertation is a continuation of data he worked on during his undergraduate programme. Gianluc hopes to provide updated information on the lane snapper's life history, which may be used as a reference when determining minimum size limits for fisheries management in Trinidad and Tobago. He also hopes that his work will highlight gaps in our local and regional fisheries data, which may be essential for stakeholders to understand before formulating regulations and management plans.

Outside of his academics, Gianluc and his former colleagues from UTT created a local NGO by the name of Sustainable Knowledge and Your Environment (SKYE) where they regularly host educational events for primary and secondary school children on organic food production and environmental sustainability.

Wednesday 31st March, 2021 at 10:00 a.m.