Mining the behavioural reality of fish-fisher interactions to understand vulnerability to hook-and-line fishing

PhD thesis

Capturing a fish with hook-and-line angling depends on the behaviour of the fish. Selective capture based on heritable behavioural traits may have ecological and social ramifications for both fish populations and fishing communities, but the behavioural components of angling vulnerability are not clear-cut. Vulnerability to angling can be conceptualized as a threefold combination of the internal state of the fish (e.g., hunger, or aggression), the encounter with the gear and the quality of the gear itself which are modified by traits of the environment and the fish. Accordingly, greater activity and space use is expected to increase vulnerability via an elevated encounter probability with fishing gear. However, behaviourally selective angling may also interact with the searching ability, lure choice and general angling skill of the anglers. My objective was to better understand the role of movement and space use behaviours in driving angling vulnerability through empirical tests in the wild. I formed my hypotheses from clear simulation based predictions made by Alós et al., (2012). I measured the behaviour and angling vulnerability of four species (viz. carp, Cyprinus carpio tench, Tinca tinca, perch, Perca fluviatilis, and northern pike, Esox lucius) using high resolution acoustic telemetry in a wholelake study system. Angling gear and technique were standardized and perch specifically were targeted by volunteer anglers in individual GPS tracked boats to understand how angler skill affects the behavioural basis of vulnerability. I have therefore contrasted behaviourally selective angling in benthivorous cyprinids (carp and tench) targeted from fixed angling sites, an active social top predator (perch) targeted by freely searching anglers and an ambush predator (northern pike) also targeted by freely searching anglers. I found no evidence for selection by angling against repeatable carp, tench or perch activity or movement traits as encounter was unrelated to angling vulnerability. In the case of perch, vulnerability strongly related to habitat choice as shown by a clear latitudinal division of captured and uncaptured perch. Angler skill level did not modify which perch behaviours were captured, but the higher skilled perch anglers enacted a greater mortality on the population and therefore stronger selection. Finally, large pike with larger activity space sizes were more vulnerable to angling and an encounter effect cannot be ruled out. In conclusion, the critical behaviours distinguishing angling vulnerability, upon which selection should be expected, frequently operate after a fish-fisher encounter, but the importance of fish-fisher encounters for vulnerability may be species and fishery specific.

Monk, C. T. (2018). Mining the behavioural reality of fish-fisher interactions to understand vulnerability to hook-and-line fishing. Dissertation, Humboldt-Universität zu Berlin

Published : 2018
Appeared in : Dissertation, Humboldt-Universität zu Berlin