Research Article: Historical changes (1905-present) in catch size and composition reflect altering fisheries practices on a small Caribbean island

Date Published: June 13, 2019

Publisher: Public Library of Science

Author(s): Mark J. A. Vermeij, Kelly R. W. Latijnhouwers, Faisal Dilrosun, Valérie F. Chamberland, Caroline E. Dubé, Gerard Van Buurt, Adolphe O. Debrot, Heather M. Patterson.

http://doi.org/10.1371/journal.pone.0217589

Abstract

Effective assessments of the status of Caribbean fish communities require historical baselines to adequately understand how much fish communities have changed through time. To identify such changes and their causes, we compiled a historical overview using data collected at the beginning (1905–1908), middle (1958–1965) and end (1984–2016) of the 20th century, of the artisanal fishing practices and their effects on fish populations around Curaçao, a small island in the southern Caribbean. We documented historical trends in total catch, species composition, and catch sizes per fisher per month for different types of fisheries and related these to technological and environmental changes affecting the island’s fisheries and fish communities. We found that since 1905, fishers targeted species increasingly farther from shore after species occurring closer to shore had become rare. This resulted in surprisingly similar catches in terms of weight, but not composition. Large predatory reef fishes living close to shore (e.g., large Epinephelid species) had virtually disappeared from catches around the mid-20th century, questioning the use of data from this period as baseline data for modern day fish assessments. Secondly, we compared fish landings to in-situ counts from 1969 to estimate the relative contributions of habitat destruction and overfishing to the changes in fish abundance around Curaçao. The decline in coral dominated reef communities corresponded to a concurrent decrease in the abundance and diversity of smaller reef fish species not targeted by fishers, suggesting habitat loss, in addition to fishing, caused the observed declines in reef fish abundance around Curaçao.

Partial Text

Historical accounts by the earliest European explorers of Caribbean waters report large abundances of manatees, large sharks, sea turtles and monk seals that are unimaginable given the current state of these ecosystems (e.g., [1–3]). The unprecedented depletion of nearshore marine life around Caribbean islands is arguably best illustrated by the changes in their fish communities. Unsustainable human exploitation has resulted in present day fish communities that differ markedly in composition and abundance from fish communities observed only decades ago [2, 4–8]. Larger (predatory) fish have become especially rare and no longer affect other reef community members through behavioral and trophic interactions, a phenomenon referred to as “ecological extinction” [9, 10]. The disappearance of large fish has been linked to an increase in former prey species (prey release) [10, 11], including those that can feed on or destroy living corals (e.g., [12, 13]), an increase in disease prevalence in fishes as infected hosts are no longer effectively culled [14] and reductions in reef accretion due to the historical overfishing of parrotfishes [15]. Therefore, over-exploitation of (predatory) fishes has resulted in cascading effects that have affected the functioning of reef ecosystems as a whole [9, 16, 17].

Marine species in the waters around Curaçao, adjacent islands and the rest of the Caribbean have been subject to exploitation by humans for millennia [2, 25, 53]. Even in pre-Columbian times, exploitation of marine organisms, especially large fishes and turtles, was already unsustainable on several Caribbean islands [5], but it was not until after the arrival of Europeans in the region that increasing human population size and technological developments translated into major overfishing, particularly during the 20th century (e.g., [3, 54, 55]).

The average CFM has remained surprisingly constant over the last century on Curaçao when considering landing sizes for handline fisheries. However, information in total landings, as volumes, proved to be misleading as fishers targeted new species through time after earlier targeted species had become rare, a phenomenon known as “sequential overfishing”. Total landings seem therefore only appropriate for species-specific fisheries (e.g., herrings, sardines) whereby fishers do not compensate losses in one species by shifting to others (e.g. spearfishers) or by expanding the area where harvesting takes place (e.g., line fishing). Our study demonstrates how understanding the historical changes in fish community structure clearly requires a context broader than fishing alone, given the decline in certain reef fishes such as cardinal and hawkfishes that are not targeted by fishing, but with a strong dependence on live coral which has decreased enormously in the Caribbean over the last decades. This information is important when designing management strategies on small islands like Curaçao, because the amount of local support for such actions increases as persons or processes responsible for an undesired decline in marine resource (such as reef fish) are correctly identified. Fishers are probably more likely to support restrictive management action (i.e., local no-take zones) as they often feel they are singled out and accused of being solely responsible for decreases in fish abundance. New and existing regulations aimed at improving the health of Curaçaoan fish communities through land- and ocean-based regulations are, however, unlikely to achieve these improvements given the weak enforcement of fisheries regulations on Curaçao [34]. While certain fish species have declined almost solely due to overfishing (e.g., large grouper species), habitat degradation has resulted in the reduced abundance of especially obligate coral-associated fishes around small Caribbean islands such as Curaçao.

 

Source:

http://doi.org/10.1371/journal.pone.0217589

 

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