Abstract
The target species (Aphia minuta and Pseudaphya ferreri) of the transparent goby fishery on Mallorca Island (Balearic Islands, western Mediterranean) are currently discarded when the maximum daily catch is exceeded or when the sorting process is unworkable. The mortality suffered by this discarded fraction remains unknown, although it may be important for resource management. Accordingly, the aims of this study were to (1) assess the environmental drivers of the relative post-release survival of the discarded target species and (2) test the correlations between post-release survival and two behavior-related variables (swimming speed and its increase after a stimulus, assessed via video recording). To do so, mortality of the target species from 47 hauls sampled under normal fishing boat operations was monitored when the gear was onboard and after a few hours. At the reference level (an average depth of 25.7 m and temperature of 15.7 ºC), the immediate survival was 99.9% (95% CI: 97.9 to 100%), but the estimated post-release survival decreased to 47.2% (33.8 to 65.8%). Relative post-release mortality doubled when the water temperature increased by 2.8 ºC or when the fishing depth increased up to 32 m. Furthermore, the swimming speed of the target species was significantly correlated with the estimated post-release survival; thus, this vitality metric may offer a promising strategy for more easily estimating post-release mortality in other fisheries.
Highlights
A large proportion of global commercial fishery catches are discarded and returned to the sea due to regulatory, economic or other reasons [1]
The catch of a given haul was classified into one of three categories according to the fisher’s expertise: 1) more than 90% of A. minuta, 2) more than 90% of P. ferreri or 3) mixed catch
The present study introduces an approach for assessing the relative post-release mortality of two target species (A. minuta and P. ferreri) in the transparent goby fishery and the environmental drivers of post-release fish mortality
Summary
A large proportion of global commercial fishery catches are discarded and returned to the sea due to regulatory, economic or other reasons [1]. Discards constitute a waste of natural resources, and they negatively affect both the sustainability of marine ecosystems and the economic viability of fisheries [2, 3]. The problem of discarding in European fisheries has received increasing public attention [4], and the current Common Fisheries Policy. Post-release mortality of transparent goby fishery: Environmental drivers and vitality metrics (MINOUW). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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