Combining in-trawl video with observer coverage improves understanding of protected and vulnerable species by-catch in trawl fisheries

Genetic isolation between coastal and fishery‐impacted, offshore bottlenose dolphin (Tursiops spp.) populations

“…Finally, underwater video footage collected inside trawl nets (Jaiteh et al . ), as well as photo‐identification data from around trawlers (Allen ), suggests that a community of dolphins within the broader population may show fidelity to foraging around trawlers. Estimating the number of individuals interacting with the trawlers is also required to better assess the level of impact this putative community faces.…”

“…This might also allow: the detection of any changes in population size due to fishery-caused mortalities (c.f., Garza & Williamson 2001); the determination of whether closely related individuals are subject to incidental capture (c.f., Mendez et al 2010), which can exacerbate the demographic impacts of bycatch in highly social species, such as delphinids (Wade et al 2012); and, the definition of appropriate management units for pelagic dolphins across northern Australia (c.f., Bilgmann et al 2014). Finally, underwater video footage collected inside trawl nets (Jaiteh et al 2014), as well as photo-identification data from around trawlers (Allen 2015), suggests that a community of dolphins within the broader population may show fidelity to foraging around trawlers. Estimating the number of individuals interacting with the trawlers is also required to better assess the level of impact this putative community faces.…”

Underwater observations of seal–fishery interactions and the effectiveness of an exclusion device in reducing bycatch in a midwater trawl fishery

“…The present study successfully applied underwater video technology to describe the behaviour of fur seals in the trawl gear, evaluate the outcomes of individual interactions and assess the effectiveness of a simple modification of the exclusion device in mitigating mortalities. There are relatively few other studies that have directly examined the nature of the interactions and, where information is available, it has tended to be based on relatively few observations (Wilkinson et al 2003;Northridge et al 2005;Hamer and Goldsworthy 2006;Jaiteh et al 2013Jaiteh et al , 2014Wakefield et al 2014).…”

“…This has clear ramifications for the reporting of bycatch -even with a high level of observer coverage most, if not all, of the interactions would have gone undetected. Jaiteh et al (2014) also noted this issue in respect to the dolphin bycatch in a demersal trawl fishery employing a bottom opening escape hatch. Dropout or the passive ejection of mortalities through escape openings is not, however, limited to bottom opening configurations and has been reported for top opening escape hatches (Wakefield et al 2014;Robertson 2015).…”

Camera technology for monitoring marine biodiversity and human impact

“…A combination of onboard video observations and in‐trawl video systems can improve bycatch estimates (Jaiteh et al . ), thereby providing crucial information toward effective management, although this is complicated in part by unseen underwater gear‐related injury and death to fish. Trawl fisheries in particular also discard large quantities of undesirable (or unlandable) catch, which not only has direct negative consequences for target and non‐target stocks but may also have ecosystem‐level effects (Bicknell et al .…”