Elsevier

Biological Conservation

Volume 241, January 2020, 108395
Biological Conservation

Perspective
Should we protect extirpated fish spawning aggregation sites?

https://doi.org/10.1016/j.biocon.2019.108395Get rights and content

Highlights

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    Fish spawning aggregations (FSAs) are disappearing through overfishing.

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    It is currently unclear if there is value in protecting extirpated FSAS.

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    We supplement the best database on FSAs available.

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    Recovery of FSAs is possible in areas with effective management.

Abstract

Some locations have extraordinary ecological and conservation significance and subsequently need protection to guarantee the persistence of species that depend on them. Fish Spawning Aggregation (FSA) sites, where fish congregate to breed, are examples of such places, but are being extirpated worldwide through overfishing. Although transient FSA sites figure prominently as priority areas for conservation, extirpated aggregations, that due to current low abundance at spawning times are no longer recognizable as FSAs, represent a dilemma for managers. Given the limited resources available for conservation actions, should we protect extirpated FSAs or omit them from spatial management plans? Here we present two contrasting points of view, look into the mechanisms associated with the emergence and maintenance of aggregation sites, and review available evidence of recovery in the field. Of the 53 extirpated FSA sites examined, 9 (17%) reported recovery, always after strict management was implemented. All recovered sites were located in the wider Caribbean and western Atlantic. We make the case that extirpated FSAs seem to have the potential to recover and their protection may provide a cost effective way to help rebuild fisheries. It is unclear, however, if a remnant population is needed to allow recovery. Current methods used to monitor and assess FSA status and extirpation are not consistent, hindering site trend analysis, between-site comparisons and meta-analysis. We suggest that monitoring and management should be made more consistent and strengthened to boost FSA recovery.

Section snippets

Fish spawning aggregation sites

Certain places are critical for species to complete their life cycle. Many animals gather in specific places to breed, nest or rear their young, and return to these sites repeatedly for generations. Salmon return to their natal rivers for spawning (Ueda, 2013), turtles use the same beaches for nesting (Broderick et al., 2007) and some penguin species undertake long migrations to find the right place to breed and rear their young (Ancel et al., 2013). These sites are crucial to guarantee the

The value of fish spawning aggregation sites

FSA sites are critical both in an ecological and conservation context. Because many fishes depend on these sites to produce the next generation, FSA sites are crucial for the persistence of fish populations and have a disproportionately large ecological and conservation value (Erisman et al., 2017b).

Due to their spatial and temporal predictability and the high catch rates at spawning sites, transient FSAs (the focus of this article) are the target of both commercial and small-scale fishers, who

Managing FSAs

Effective management measures are urgently needed to protect exploited FSAs, halt their decline, and support fish populations (Erisman et al., 2017b; Johannes et al., 1999). FSAs can be managed using combinations of standard catch and effort controls and seasonal or spatial closures. The appropriate approach depends on intrinsic (biological) and extrinsic (fisheries and socio economic) factors of the specific species and its fishery (Grüss and Robinson, 2015; Sadovy de Mitcheson, 2016). Effort

Extirpated FSAs, a conservation dilemma

Given the limited budget available for conservation actions, the inclusion of extirpated FSA sites in spatial management plans represents a dilemma. Should these sites be included? Although recent FSA literature advocates for the protection of existing aggregation sites (Erisman et al., 2017b) and raised awareness of their alarming decline (Sadovy de Mitcheson et al., 2008), there is currently no guidance on how to proceed when these two issues meet.

While drafting a spatial management plan one

The case for protecting extirpated FSAs: predictable unique sites

Intrinsic environmental characteristics make FSA sites ideal locations to maximize reproductive success. Because of their predictability, such sites should be protected even if aggregations have ceased to form there. As the location of FSAs is temporally stable, with many spanning several decades and others nearly 100 years (Claro and Lindeman, 2003; Colin, 2012a; Craig, 1969), it is therefore likely that extirpated FSA sites will be “found again” or “reform” and become functional if

The case against investing limited resources to protect extirpated FSAs: critical thresholds and loss of recovery potential

Extirpated FSAs might never re-form. Species with characteristic social behavior such as group mating may be at increased risk of extirpation under heavy exploitation due to Allee effects and depensatory dynamics (Sadovy de Mitcheson and Erisman, 2012). Under low densities critical mass that triggers normal courtship rituals and spawning may not be reached (Carolsfeld et al., 1997; Sadovy de Mitcheson, 2016). For example, in the Caribbean, Nassau grouper has not been reported to spawn in

Evidence from field studies

Evidence of recovery of extirpated FSAs is scarce and it has never been summarized in the literature. Although a recent review indicates there is strong evidence of recovery of extirpated aggregations (Erisman et al., 2017b), most of the literature cited reported increases in abundances after protection, rather than recovery after extirpation has occurred, i.e., in Erisman's study, only three examples of recovery after true extirpation are presented (Beets and Friedlander, 1999; Burton et al.,

Discussion

The collected evidence suggests extirpated FSAs do have the potential to recover after spatial closures have been implemented, supporting the continued protection of these sites after extirpation, and their inclusion in future spatial management plans. Although recovery of extirpated sites was overwhelmingly related to the presence of strong management actions, not all protected aggregations exhibited recovery. Lack of recovery in protected FSAs could be associated with several factors,

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

We are grateful to people that contributed to this work providing key insight into some FSA sites and (sometimes obscure) references: Alejandro Acosta, Andres Alegría, Michael Burton, Don DeMaria, Ron Hill, Cristopher Koenig, Ken Lindeman, Brian Luckhurst, Deb Levinson, John Reed. SF was supported in part by the Summit Foundation, MARFund and the Walton Family Foundation. MAP was supported by an Australian Government Research Training Program Scholarship.

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