Scavenging deep demersal fishes of the Porcupine Seabight, north-east Atlantic: observations by baited camera, trap and trawl

Abstract

Demersal fishes on the continental rise and slope were sampled by trawl, baited trap and a baited camera. Seventy-one different species were trawled, but only 18 species approached baits. At rise soundings (4100 m to 2250 m) Coryphaenoides (Nematonurus) armatus was dominant at baits and comprised 41·5% of the trawl catch. On the slope (<2250 m) Synaphobranchus kaupi was dominant at baits and comprised 32·7% of the trawl catch. At 1500–2501 m Antimora rostrata competed at baits and comprised 5–10% of trawl catches. At 1500–1650 m Centroscymnus coelolepis also consumed baits but was not captured by trawl. For C. (N.) armatus abundance was proportional to tarr2 (where tarr= arrival time), demonstrating that arrival time of the first fish at baits provides an estimate of population density. Maximum estimated abundance at 2897 m was 877 km-2, more than five times the abundance on the abyssal plain. Halosauropsis macrochir, Lepidion eques, Coryphaenoides guentheri, Gadiculus argenteus and Coryphaenoides rupestris were important in trawl samples but absent or rare at baits.

Trends in body size across an environmental gradient: A differential response in scavenging and non-scavenging demersal deep-sea fish

“…Small individuals of A. rostrata and C. armatus are not attracted to baited cameras at depths, where they are abundant in trawls (Priede et al 1994;Collins et al 1999) and this is supported by the limited diet data (Mauchline & Gordon 1984;Martin & Christiansen 1997). Small S. kaupi are attracted to baited cameras (Priede et al 1994), but diet studies do indicate an increase in dependence on scavenging in larger fish (Gordon & Mauchline 1996). This supports the prediction that at a particular food density, there will be a threshold minimum size necessary to support a scavenging lifestyle.…”

Large decline in the abundance of a targeted tropical lethrinid in areas open and closed to fishing

“…Relative abundance counts for Lethrinus miniatus from each stereo BRUV deployment were obtained by examining footage from the right camera only. Relative abundance is defined as the maximum number of L. miniatus (MaxN) present in the field of view of the right camera at the same time (Priede et al 1994, Cappo et al 2004). This measure avoids repeated counts of the same individual and gives a conservative measure of relative abundance, as often only a portion of the total number of individuals in the area may be viewed at one time (Willis et al 2000).…”

Juvenile gadoid habitat and ontogenetic shift observations using stereo-video baited cameras

“…All epibenthic and demersal fauna identified were quantified to the lowest taxonomic level possible. The maximum number of individuals of the same species appearing in a frame at the same time (MaxN) was used as a measure of relative abundance (Priede et al 1994, Watson et al 2005, Cappo et al 2006. MaxN avoids repeat counts of individuals reentering the field of view (Priede et al 1994, Watson et al 2005.…”