Assessing relative post-release mortality for the transparent goby fishery: Environmental drivers and the utility of vitality metrics

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 postrelease mortality in other fisheries.

Validating the growth increment periodicity in the otoliths of three small progenetic gobies

“…According to our results (Table 1), these progenetic gobies are very sensitive to handling caused by fishing and experimental acclimatization, and C. linearis is the most sensitive. Depth and temperature at fishing seem to be the most important environmental drivers in the survival of target species of the transparent goby fishery (Gil et al 2020). Injuries produced by changes in pressure (barotrauma) and temperature shock, especially at temperate and tropical latitudes, have been reported to affect survival of fishes subjected to fisheries activities (Giomi et al 2008, Curtis et al 2015, Gil et al 2020).…”

“…Depth and temperature at fishing seem to be the most important environmental drivers in the survival of target species of the transparent goby fishery (Gil et al 2020). Injuries produced by changes in pressure (barotrauma) and temperature shock, especially at temperate and tropical latitudes, have been reported to affect survival of fishes subjected to fisheries activities (Giomi et al 2008, Curtis et al 2015, Gil et al 2020). Survival at landing and after the first week seems to be affected by these drivers.…”

Estimating post-release mortality of long-line caught tropical tunas in the Pacific Ocean

“…Estimated rates of Frelease vary considerably across taxa, gear types and environments (e.g. Eddy et al, 2016;Ellis et al, 2017;Musyl and Gilman, 2019;Nunes et al, 2019;Gil et al, 2020) and mortality due to the fishing interaction can be immediate or delayed for more than one-month (Swimmer et al, 2006;Musyl and Gilman, 2018;Schweitzer et al, 2020).…”