European spiny lobster recovery from overfishing enhanced through active restocking in Fully Protected Areas

Abstract

Fully protected areas (FPAs) help preserving biodiversity and reversing the global decline of fishery resources. Stocks of the European spiny lobster Palinurus elephas (Fabr. 1787), among the most precious gourmet seafood worldwide, are currently facing a dramatic decline. Previous attempts of recovery based on fishery restrictions or active post-larval restocking in marine reserves provided unsuccessful outcomes. Here we present results of a 5-year restocking program carried through a Collaborative Fishery Research (CFR) project, in three ad-hoc established FPAs replenished using below-legal size wild juveniles. Results showed that Catch per Unit Effort (CPUE) in terms of both density and biomass burst (by ca. 300-700%) just 2 years since FPAs establishment, regardless of location. We also report tangible spillover effects (ca. 30-50% increase in density and biomass CPUE outside the FPAs) by the end of the program. Data from a 15-years lasting monitoring of a pilot FPA established in 1998, where the restocking protocol was conducted and protection kept in force once restocking ceased, demonstrated the persistence in time of restocking' benefits. We foster that creation of FPAs assisted with local restocking under oriented CFR programs can represent an option for the recovery of European spiny lobster stocks from overfishing.

Figure 1

Map of the study area. Yellow dots represent replicates (i.e., set of trammel nets) performed inside FPAs, where fishing activities are prohibited. Blue dots represent set performed outside FPAs, in neighboring fishing grounds comprised within a 5 nautical miles radius from FPAs’ center, where below-legal size lobsters were released. The map was generated using QGIS software, version 2.18. 64 bit; https://www.qgis.org/.

Figure 2

Plot showing annual CPUE (gr/50 m ± s.e.) and nCPUE trends (n. ind/50 m ± s.e.) inside (upper graph) and outside (lower graph) FPAs borders before the beginning (time zero) and during restocking (time 1, 2, 3, 4, 5).

Figure 3

Forest Plot showing cumulative impacts of FPAs (ln–response ratio; mean ± 95% confidence intervals). Red circles: non-significant ratios; green circles: significant ratios; blue circles: overall ratio, across time. Cumulative effects are significant if confidence intervals do not overlap zero.

Figure 4

Forest Plot showing cumulative impacts of restocking in the two FPAs of Castelsardo (ln–response ratio; mean ± 95% confidence intervals). Red circles: non-significant ratios; green circles: significant ratios. Cumulative effects are significant if confidence intervals do not overlap zero.

Figure 5

Forest Plot showing cumulative impacts in Su Pallosu FPA (ln–response ratio; mean ± 95% confidence intervals). Red circles: overall ratio reported in the pilot study started in 1998 and concluded in 2005; green circles: significant ratios from year 2006 to 2013.