Testing and implementation of an exclusion device for mitigating the incidental capture of sea lions in the Chilean small-scale trawl hake fishery

Abstract

In recent years, the Chilean hake (Merluccius gayi gayi) trawl fishery has implemented measures to reduce discards, bycatch, and incidental captures. In the past ten years, the incidental capture of South American sea lions (Otaria flavescens) (SASLs) has become a significant concern, particularly for the small-scale fleet operating from San Antonio in central Chile. To address this issue, a sea lion exclusion device (SLED) was introduced for trawl nets. This paper describes an experiment that was designed to assess the effectiveness of SLEDs. Records of the incidental capture of SASLs and mortality from scientific observers monitoring this small-scale trawl fleet were also analyzed. The results of the experiment indicated that SLEDs greatly reduced incidental captures of SASLs without affecting the capture of the target species. However, given that there was only one year of overlap between non-SLED and SLED data, these findings should be interpreted with caution. The data from scientific observers from 2015 to 2022 suggested a consistent decrease in the incidental capture of SASLs with the use of SLEDs, supporting the potential effectiveness of this mitigation measure.