Dynamic enforcement of bycatch via reproductive value can increase theoretical efficiency
Résumé
Managing marine systems is challenging, as many marine species are highly mobile. Albatross exemplify this
paradigm, overlapping multiple threats at sea, including bycatch. The typical characterization of bycatch, the
number of individuals, ignores the long-term, population-wide repercussions of bycatch. Including an estimate of
the reproductive value (RV, the loss of future reproductive contributions, given bycatch) is a complementary
tool, incorporating the population-wide repercussions of bycatch. While bycatch management via dynamic
spatial management allows management boundaries to move, it requires monitoring and enforcement to be
effective. We provide a proof of concept to optimize bycatch enforcement activities by dynamically targeting
areas of concentrated future productivity characterized by RV. This paper examined a population of blackbrowed
albatross (Thalassarche melanophris) as a case study. We calculate RV and apply it to at-sea distributions.
This creates spatiotemporally explicit surfaces used to prioritize times and locations for bycatch mitigation
enforcement. Dynamic enforcement has greater theoretical efficiency than static enforcement, but this difference
decreases with increasing population-wide RV subject to enforcement. Though there are implementation challenges,
many can be reduced with existing tools providing various opportunities. Incorporating RV when
characterizing the impacts of bycatch on a population and strategically applying dynamic bycatch enforcement
based on RV can be a powerful, efficient component of dynamic ocean management.