An experimental evaluation of the effect of escape gaps on the quantity, diversity, and size of fish caught in traps in Montserrat

• Published in: PloS one Vol. 16; no. 12; p. e0261119
• Main Authors: Flower, Jason, Estep, Andy, James, Keinan, Ramdeen, Robin, Runge, Claire A, Thomas, Lennon, Lester, Sarah E
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 10-12-2021; Public Library of Science (PLoS)
• Subjects: Animals; Biology and Life Sciences; Biomass; Body Size; Chi-square test; Climate change; Commercial fishing; Coral reef ecology; Coral Reefs; Earth Sciences; Ecology and Environmental Sciences; Environmental aspects; Environmental science; Fish; Fish industry; Fish traps; Fisheries; Fisheries management; Fishes; Fishes - physiology; Fishing; Fishing equipment; Fishing gear; Hauling; Identification and classification; Methods; Observations; Physical Sciences; Protection and preservation; Research and Analysis Methods; Selectivity; Species diversity; Species richness; Statistical analysis; Sustainability; Traps; Volcanoes; West Indies; West Indies; United States; La Jolla California; Santa Barbara California; California; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0261119

Coral reef fisheries are vital to the livelihoods of millions of people worldwide but are challenging to manage due to the high diversity of fish species that are harvested and the multiple types of fishing gear that are used. Fish traps are a commonly used gear in reef fisheries in the Caribbean and other regions, but they have poor selectivity and frequently capture juvenile fish, impacting the sustainability of the fishery. One option for managing trap fisheries is the addition of escape gaps, which allow small fish to escape. We compared catches of traps with and without two 2.5 cm (1 inch) escape gaps on the Caribbean island of Montserrat. No significant differences were found in the mean fish length, total fish biomass, number of fish, fish species richness, and Shannon diversity index between hauls of the two trap designs, though traps with escape gaps did catch larger proportions of wider-bodied fish and smaller proportions of narrow-bodied fish. Furthermore, traps with gaps caught a smaller proportion of small-sized fish and fewer immature fish (though differences were not statistically significant). Linear mixed effect models predict that soak time (the length of time between trap hauls) increases the mean catch length, total catch biomass and total number of species in the catch. The relatively modest evidence for the effect of the gaps on catch may be explained by the long soak times used, which could have allowed most smaller-sized fish to escape or be consumed by larger individuals before hauling in both traps with and without escape gaps. Despite the small differences detected in this study, escape gaps may still offer one of the best options for improving sustainability of catches from fish traps, but larger escape gaps should be tested with varying soak times to determine optimum escape gap size.