Observed Mortality of Rainbow Trout Caught by Different Angling Techniques in Lake Taupo, New Zealand

Abstract

Angling mortality was assessed for Lake Taupo wild rainbow trout Oncorhynchus mykiss caught by four different trolling techniques and released. Observed cumulative mortalities 48–53 h after hooking were 15.3% for downrigger, 14.0% for wire line, 7.8% for lead line, and 2.2% for harling. Both immediate and delayed mortalities for each method are discussed. Ninety‐three percent of the total mortality occurred within 26 h after release. Hooking injuries, playing time, transit time, depth at capture, and fish length were not significant causes of mortality. Potential sources of bias in mortality rate estimates are discussed.

Changes in blood cortisol, glucose and lactate in carp retained in anglers' keepnets

“…Physical and physiological factors of concern include the extent of exertion during playing and landing, the physical effect of hooking and handling the fish, exposure of fish within keepnets to harmful deterioration in water quality, and the possible initiation of a physiological stress response consequent to the combined effects of capture, handling, restraint and confinement. Some information is available regarding the welfare of individual fish and the effects of angling pressure on populations of fish (Brana et al, 1992;Brobbel et al, 1996) and there are limited data available concerning mortality arising from hook damage (Bugley & Shepherd, 1991;Dedual, 1996;Dextrase & Ball, 1991;Muoneke & Childress, 1994;Malchoff & Heins, 1997) and the recovery of rod-caught fish post-capture (Ferguson & Tufts, 1992;Pankhurst & Dedual, 1994;Wilkie et al, 1996). However, the species and conditions employed in these studies are not strictly relevant to United Kingdom non-salmonid fisheries, in which catch-and-return angling is prevalent.…”

Injury and immediate mortality associated with recreational troll capture of bull trout (Salvelinus confluentus) in a reservoir in the Kootenay-Rocky Mountain region of British Columbia

“…Interestingly, a mortality rate of <1% represents one of the lowest mortality rates observed for any freshwater fish (Reviewed in Muoneke and Childress, 1994;Bartholomew and Bohnsack, 2005;Arlinghaus et al, 2007), and particularly low for salmonids (Taylor and White, 1992). One of the only other studies to evaluate immediate hooking mortality for lentic salmonids captured while trolling revealed that mortality rates ranged between 0 and 11.5% for four different trolling methods targeting rainbow trout in Lake Taupo, New Zealand (Dedual, 1996). Although none of the techniques are directly comparable to those used in the present study, they emphasize that subtle differences in technique can alter mortality estimates.…”

“…In the present study fish were captured at relatively shallow depths and no evidence of barotrauma was observed. By contrast, the only other freshwater trolling that involved anglers targeting salmonids recorded barotrauma in fish caught from greater depths (Dedual, 1996). Fish that fought for longer periods were more likely to lose equilibrium upon landing, but those also tended to be the largest fish.…”

“…Although none of the techniques are directly comparable to those used in the present study, they emphasize that subtle differences in technique can alter mortality estimates. In the Dedual (1996) study, the variation in mortality among techniques was attributed primarily to barotraumas, with fish captured using harling (i.e., trolled flies) techniques on the surface having no mortality and those captured at depths exceeding 35 m via downrigger experienced 12.5% immediate mortality. Fish in the present study were captured at depths of 10 m or less which is on the shallow side of the depth ranges used in the Dedual (1996) study.…”

“…While casting is a popular activity for larger lentic-dwelling populations of salmonids (e.g., Holtby et al, 1992), it is also common to troll using artificial lures. Furthermore, there have been relatively few studies that have examined different hook type (i.e., barbed vs. barbless, single vs. multiple hooks) issues in freshwater trolling-based fisheries (see Dedual, 1996).…”