Drivers of spatiotemporal variability in bycatch of a top marine predator: First evidence for the role of water turbidity in protected species bycatch

1. Bycatch of protected species in static net fisheries is a global
conservation concern and is currently considered the dominant
anthropogenic threat to many marine mammal species worldwide. Effective
bycatch mitigation remains challenging, contingent on an understanding of
the underlying mechanisms that cause individuals to become entangled. 2.
We combined data collected by scientific observers and fishers to identify
predictors of seal bycatch in static net fisheries along the west,
southwest, and south coasts of Ireland. We first analysed the broad
regional and seasonal trends in seal bycatch before identifying
environmental variables that could potentially explain these patterns. 3.
Based on negative binomial generalised linear mixed effects models, the
rate of seal bycatch significantly varied with season and region, and
decreased at greater distances to major seal colonies and lower water
turbidity. 4. Synthesis and applications. Our results suggest that
distance to major seal colonies was a significant driver of the observed
regional differences in seal bycatch rates, and water turbidity a major
driver of seasonal trends. These findings will enable us to identify
future bycatch risk and target mitigation measures accordingly. This is
the first study to identify the effect of water turbidity on bycatch of a
protected marine species. Increasing net visibility in turbid waters may
provide a novel approach to mitigating against protected species bycatch
in static net fisheries.05-Nov-2019