No evidence from long-term analysis of yellowfin tuna condition that Drifting Fish Aggregating Devices act as ecological traps

Human-induced habitat modifications can severely impact the biology
and behavior of wild species. Drifting Fish Aggregating Devices (DFADs),
used by industrial purse seine tropical tuna fisheries, significantly
increased the number of floating objects found in the open ocean, to
which tropical tuna associate. This habitat change raised concerns over
the risk of modifying the behavior and altering the biology of tuna and
other associated species (the so-called ecological trap hypothesis).
Relying on a time-series from 1987 to 2019 of more than 25,000 lengthweight
samples collected in the western Indian Ocean, we reject the
hypothesis that the body condition (Le Cren’s relative condition factor Kn)
of yellowfin tuna (Thunnus albacares) decreased concurrently with the
increased number of DFADs. This result suggests the absence of negative
long-term impacts of DFADs on the condition of tuna. As other factors
may have counteracted possible negative effects of DFADs, we
recommend a long-term monitoring of habitat, biological and behavioral
parameters of tunas to detect any critical change.