Behavior-dependent selectivity of yellowtail flounder (Limanda ferruginea) in the mouth of a commercial bottom trawl

Abstract

Abstract-To improve the efficiency of a commercial bottom trawl for catching yellowtail flounder (Limanda ferruginea), we studied the behavior of individuals in the middle of the trawl mouth. Observations were conducted with a high-definition camera attached at the center of the headline of a trawl, during the brightest time of day in June 2010 off eastern Newfoundland. Behavioral responses were quantified and analyzed to evaluate predictions related to fish behavior, orientation, and capture. Individuals showed 3 different initial responses independent of fish size, gait, and fish density: they swam close to (75%), were herded away from (19%), or moved vertically away from (6%) the seabed. Individuals primarily swam in the direction of initial orientation. No fish were oriented against the trawling direction. Fish in the center of the trawl mouth tended to swim along the bottom in the trawling direction. Only individuals that were stimulated to leave the bottom were caught. Individuals in peripheral locations within the trawl mouth more often swam inward and upward. Fish that swam inward were twice as likely to be caught. Fish size, gait, and fish density did not influence the probability of capture. A trawl that stimulates yellowtail flounder to orient inward and leave the bottom would increase the efficiency of a trawl.

A physiological perspective on fisheries‐induced evolution

“…The relevance of this swim performance‐based mode of selectivity is dependent on fish engaging in an optomotor response (a reflexive behaviour thought to reorient a swimming fish after displacement from its desired horizontal course; Kim & Wardle, ) in which fish swim to maintain station with the trawl, often oriented adjacent to the trawl doors, until they drop back within the net. While this is often observed (Kim & Wardle, ; Rose, ), individual variation in the response to gears is also frequent (Underwood, Winger, Fernö, & Engås, ; Yanase, Eayrs, & Arimoto, ) and often predicts the chances of capture for individual fish. Whether these behavioural responses correlate with heritable physiological traits remains unclear, although individual's orientation prior interaction with the trawl gear, and density of conspecifics, can influence fish responses to trawls (Rose, ; Underwood et al., ).…”

“…While this is often observed (Kim & Wardle, ; Rose, ), individual variation in the response to gears is also frequent (Underwood, Winger, Fernö, & Engås, ; Yanase, Eayrs, & Arimoto, ) and often predicts the chances of capture for individual fish. Whether these behavioural responses correlate with heritable physiological traits remains unclear, although individual's orientation prior interaction with the trawl gear, and density of conspecifics, can influence fish responses to trawls (Rose, ; Underwood et al., ). This would suggest that responses to trawls are influenced by external environment, which could dampen selection on traits correlated with swim performance.…”

Behavioural responses to human‐induced change: Why fishing should not be ignored

“…Exceptions that did look at differences in behaviour between captured fish and escapees in natural settings are Underwood, Winger, Fernö, and Engås's () study on yellowtail flounder, Limanda ferruginea , in Newfoundland and Kim and Wardle's () study on haddock, saithe, mackerel, cod and flatfish. Yellowtail flounders exhibited three different behavioural responses to an approaching trawl resulting in different catchability.…”

Development of a Video Trawl Survey System for New England Groundfish

“…Similarly, Albert et al (2003) classified fish in front of a survey trawl as "certain Greenland halibut," "certain flatfish," or "uncertain flatfish." Underwood et al (2011Underwood et al ( , 2015 classified flatfish in their video as either Yellowtail Flounder or "unidentified flatfish" and used the pointed snout of the Yellowtail Flounder as an identifying characteristic. Underwood et al (2011) achieved 72% and 46% classification accuracy for Yellowtail Flounder using an HD and standard-definition (SD) camera, respectively.…”

“…Optical approaches have been used to examine the behavior of fish in and around otter trawls and to estimate the efficiency of trawls (e.g., Godø et al 1999;Albert et al 2003;Piasente et al 2004;Churnside et al 2012;Bryan et al 2014;Underwood et al 2015). Recent studies have used cameras to identify, measure, and quantify fish passing through a trawl net.…”