So Long and Thanks for All the Fish: Overexploitation of the Regionally Endemic Galapagos Grouper Mycteroperca olfax (Jenyns, 1840).

Paolo Usseglio,Anna Schuhbauer,Johanna Zimmerhackel,Tyler Eddy,Pelayo Salinas-De-León,Alan M Friedlander,Haruko Koike,Benjamin Ruttenberg

doi:10.1371/journal.pone.0165167

Abstract

The regionally endemic Galapagos Grouper, locally known as bacalao, is one of the most highly prized finfish species within the Galapagos Marine Reserve (GMR). Concerns of overfishing, coupled with a lack of fishing regulations aimed at this species raises concerns about the current population health. We assessed changes in population health over a 30-year period using three simple indicators: (1) percentage of fish below reproductive size (Lm); (2) percentage of fish within the optimum length interval (Lopt); and (3) percentage of mega-spawners in the catch. Over the assessed period, none of the indicators reached values associated with healthy populations, with all indicators declining over time. Furthermore, the most recent landings data show that the vast majority of the bacalao caught (95.7%,) were below Lm, the number of fish within the Lopt interval was extremely low (4.7%), and there were virtually no mega-spawners (0.2%). Bacalao fully recruit to the fishery 15 cm below the size at which 50% of the population matures. The Spawning Potential Ratio is currently 5% of potential unfished fecundity, strongly suggesting severe overfishing. Our results suggest the need for bacalao-specific management regulations that should include minimum (65 cm TL) and maximum (78 cm TL) landing sizes, slot limits (64–78 cm TL), as well as a closed season during spawning from October to January. It is recognized that these regulations are harsh and will certainly have negative impacts on the livelihoods of fishers in the short term, however, continued inaction will likely result in a collapse of this economically and culturally valuable species. Alternative sources of income should be developed in parallel with the establishment of fishing regulations to limit the socio-economic disruption to the fishing community during the transition to a more sustainable management regime.

Highlights

Overexploitation of numerous fisheries stocks is occurring worldwide [1],while the Galapagos Archipelago is often thought as a veritable Eden teeming with charismatic fauna, it has been far from spared by overfishing, as exemplified by the sea cucumber and lobster fisheries [2,3,4].Fisheries in the Galapagos started as early as the 18th century with the targeting of marine mammals [5]
The Galapagos National Park Directorate (GNPD) granted permissions PC-19-11, PC-24-13, and PC-25-14 approving this research, animal use approval was granted by the Animal Care & Use Committee, University of Hawai‘i, under protocol number 11–1284
Under Froese’s framework, in a healthy stock it would be expected that: (1) all fish caught are larger than the size at first maturity; (2) a very large percentage of the catch within the optimum length interval; and (3) values of percentage of mega-spawners in the landings to be ~ 30–40% in a population where there are no regulations regarding maximum landing size [35], such as is the case for bacalao in the Galapagos Marine Reserve (GMR). In addition to these indicators we looked at mean length in catch, as it has been shown to be inversely correlated with fishing mortality [37]

Summary

Introduction

Overexploitation of numerous fisheries stocks is occurring worldwide [1],while the Galapagos Archipelago is often thought as a veritable Eden teeming with charismatic fauna, it has been far from spared by overfishing, as exemplified by the sea cucumber and lobster fisheries [2,3,4].Fisheries in the Galapagos started as early as the 18th century with the targeting of marine mammals [5]. Prompted mainly by the profitability of the sea cucumber and lobster fisheries, the artisanal fishing sector in the Galapagos grew dramatically by 325% to almost 1000 fishers between the years 1971 and 2000 [7]. This growth in the fishing sector was paralleled by immigration from mainland Ecuador, resulting in a rapid population increase from 1,500 people in the 1950s, to over 25,000 in 2010 [8]. Overfishing of both sea cucumbers and lobsters led to a decrease in the number of fishers since the year 2000, to an estimate of ~400 active fishers in 2012 [9,10]

Methods

Results

Conclusion