Diversification insulates fisher catch and revenue in heavily exploited tropical fisheries

Abstract

Declines in commercial landings and increases in fishing fleet power have raised concerns over the continued provisioning of nutritional and economic services by tropical wild fisheries. Yet, because tropical fisheries are often data-poor, mechanisms that might buffer fishers to declines are not understood. This data scarcity undermines fisheries management, making tropical fishing livelihoods particularly vulnerable to changes in marine resources. We use high-resolution fisheries data from Seychelles to understand how fishing strategy (catch diversification) influences catch rates and revenues of individual fishing vessels. We show that average catch weight decreased by 65% over 27 years, with declines in all nine species groups coinciding with increases in fishing effort. However, for individual vessels, catch diversity was associated with larger catches and higher fishing revenues and with slower catch declines from 1990 to 2016. Management strategies should maximize catch diversity in data-poor tropical fisheries to help secure nutritional security while protecting fishing livelihoods.

Dependency of Queensland and the Great Barrier Reef’s tropical fisheries on reef-associated fish

“…Thus, the impact of coral loss on recruitment will not be detectable in fishery statistics until several years later when the cohort recruits to the fishery. Loss of habitat complexity may also restructure food-webs in ways that can enhance or diminish the overall productivity of fisheries 49,51 , so overall catch may be stabilized by targeting of multiple species 53 . Fishery independent time-series, such as from underwater visual surveys may therefore be important to combine with fishery dependent datasets to provide reliable warning of changes in the productivity of fisheries (e.g.…”

“…6,14,27,61 . This response diversity gives fisheries resilience to environmental shocks, through the portfolio effect 53 , though overall stability of catches may be eroded 6 . It is not clear whether the GBR's line fishery would benefit from a portfolio effect, because the productivity trends observed in ref 6 were herbivore fisheries, and herbivorous fish are not an important part of the GBR catch.…”

Conservation risks and portfolio effects in mixed‐stock fisheries

“…If stocks also respond differently to specific perturbations, such biodiversity can also provide ecosystem resilience (Cline et al., 2017; Doak et al., 1998; Gunderson, 2000). Accordingly, biological diversity is increasingly viewed as a foundation of sustainable and resilient resource management systems (Biggs et al., 2012; Carpenter et al., 2009; Robinson et al., 2020). Yet, fisheries that catch multiple stocks within a stock complex, whether they be specific populations (Hilborn et al., 2003; Hutchinson, 2008) or species (Hilborn et al., 2012), may over‐exploit the less productive stocks within that complex (Burgess et al., 2013; Connors, Staton, et al.…”

“…For example, aggregate productivity is often positively associated with biodiversity in systems that range from grasslands (Cardinale et al., 2013; Hooper et al., 2005) to marine ecosystems (Dee et al., 2016; Greene et al., 2010; Worm et al., 2006). Given these positive effects of biodiversity, there have been calls for natural resource management systems, such as fisheries, to try to maximize diversity within harvests (Robinson et al., 2020).…”

Morphometrics of 39 fishes from the Seychelles artisanal fisheries

“…balancing fishing effort across a wide range of species. While such a strategy has been shown to ensure local nutritional security and protect fishing livelihoods in data-poor tropical fisheries (Robinson et al ., 2020), it challenges the work of the fishery scientists and managers through the need for basic biological data, and specifically length–weight relationships, for all targeted resources.…”