Quantitative evaluation of flatfish behavior during capture by trawl gear

The effect of net spread on the capture efficiency of a demersal survey trawl used in the eastern Bering Sea

“…This behavior was different from the majority of flatfishes, which entered the net by flipping over the footrope in an inverted or sideways orientation at a mean height of only 35 cm above the footrope. Since Bublitz (1996) was not able to distinguish among the different species from the video images, it is not clear which species exhibited these behaviors. However, if Alaska plaice tend to rise before the approaching net, their catch rates will be less affected by an elevated footrope than species that do not engage in this behavior.…”

“…One possible explanation is that this species may exhibit a different behavior than the other two species of flatfish when entering the net at the footrope. Bublitz (1996) described two distinct behavior patterns among flatfishes during trawl entry. In one of these, exhibited by 20% of the fish, the fish rose slowly in front of the approaching net to a mean height of 60 cm above the footrope.…”

Quantitative analysis of the behaviour of the flatheads (Platycephalidae) during the trawl capture process as determined by real-time multiple observations

“…The use of trawl-monitoring instrumentation and underwater cameras are primary technologies that are used to obtain relevant information about fish behaviour (Isaksen and Valdemarsen, 1994;Bublitz, 1996;Weinberg and Munro, 1999;Kim and Wardle, 2003;Reid et al, 2007). However, there are few studies available in the literature that examine the behaviour of fish from the initiation of escape response to an approaching trawl to the retention by the codend.…”

“…In turn, they are important morphological factors that determine the success or failure of target and non-target fish in evading capture and the quality of size-selectivity at every stage of the capture process (Bublitz, 1996;Kim and Wardle, 2003). The use of trawl-monitoring instrumentation and underwater cameras are primary technologies that are used to obtain relevant information about fish behaviour (Isaksen and Valdemarsen, 1994;Bublitz, 1996;Weinberg and Munro, 1999;Kim and Wardle, 2003;Reid et al, 2007).…”

Availability of deep-water fish to trawling and visual observation from a remotely operated vehicle (ROV)

“…Gear efficiency, defined as the probability that an individual that encounters the gear ends up in the catch, is determined by mesh size and reactions to the approaching gear. Most of the information on the different components of catchability comes from field studies of a few continental shelf species, in particular cod, haddock and some flatfish (Parrish et al 1962, Hemmings 1973, Walsh 1991, Wardle 1993, Engås 1994, Godø 1994, Bublitz 1996. Laboratory studies have contributed to our understanding of fish reaction to gear, with respect to swimming ability (Harden Jones 1963, He 1993, hearing spectra (Chapman 1973, Hawkins 1973 and vision (Muntz 1983).…”