Adrenocortical color darkness and correlates as indicators of continuous acute premortem stress in chased and purse-seine captured male dolphins

Myrick, Albert C.; Perkins, Peter C.

doi:10.1016/0928-4680(95)00035-6

Cited by 13 publications

(8 citation statements)

References 44 publications

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“…Dolphin mothers that are left behind during the chase may attempt to reunite with their group after the fishery interaction is terminated. However, unlike the stealthy, short duration chases associated with natural predators like sharks, tuna purse-seine chases are noisy and long in duration, including 20 min of chase and a 100 min escape response after being released from the net (Myrick & Perkins 1995). If wild dolphin mothers are only capable of achieving the maximum swim speeds exhibited by the trained dolphins in the kinematic studies, then mothers with a calf in echelon position, mothers with a calf in infant position, and near-term (0−2 wk preparturition) pregnant females, will be separated from the group by 0.73, 2.42, and 1.75 km, respectively, at the end of a 20 min 5 m s −1 chase (Fig.…”

Section: Dolphins Interacting With Etp Tuna Fisherymentioning

confidence: 99%

Altered swimming gait and performance of dolphin mothers: implications for interactions with tuna purse-seine fisheries

Noren¹

2013

Mar. Ecol. Prog. Ser.

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Physical constraints while carrying an infant represent one of many reproductive costs. For bottlenose dolphins Tursiops truncatus, near-term pregnancy and 'carrying' a calf in eche lon position (calf alongside mother's mid-lateral flank) alter maternal swimming gait and performance. As calves mature an alternate form of 'carrying', infant position (calf underneath mother's tailstock) dominates. To complete our understanding of locomotion during motherhood in dolphins, kinematics (peak-to-peak stroke amplitude, A, and tailbeat oscillation frequency, f) and performance (swim speed, V) while 'carrying' a calf in infant position were quantified. The relationship (slope) for A and V differed between solitary swimming and swimming with a calf in infant position (Z = −1.706, p = 0.088) as did the relationship (slope) for f and V (Z = −3.699, p < 0.001). Compared to solitary swimming (2.17 ± 0.02 m stroke −1 ; n = 166), mothers 'carrying' a calf in infant position had diminished distance per stroke (1.82 ± 0.07 m stroke −1 ; n = 27, t = 5.209, df = 191, p < 0.001; means ± SE) concomitant with a significant reduction (54%) in average swim speed (n = 27, 166, T = 629.00, p < 0.001). These results have implications for dolphins that interact with tuna purse-seine fisheries in the Eastern Tropical Pacific (ETP). Dolphins 'carrying' a calf may be unable to achieve speeds sustained by groups evading fishermen. To maintain proximity with the group, mothers may become separated from their calf. Permanently separated dependent calves represent unobserved mortality events, which may partially explain the non-recovery of depleted ETP dolphin populations.

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Section: Dolphins Interacting With Etp Tuna Fisherymentioning

confidence: 99%

Altered swimming gait and performance of dolphin mothers: implications for interactions with tuna purse-seine fisheries

Noren¹

2013

Mar. Ecol. Prog. Ser.

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“…Subsequent examination and sampling of Longissimus dorsi and hypaxial muscle from 65 dolphins killed in ETP tuna purse-seines found "no evidence of myopathy" (Cowan & Walker, 1979), but this sample size is too small to -220 -definitively eliminate the possibility of capture myopathy affecting ETP dolphins at the population level. Another study suggested that examination of adrenal glands might provide a measure of fishery-related stress (Myrick & Perkins, 1995).…”

Section: Research Prior To the Idcpa Programmentioning

confidence: 99%

“…The chase portion of the set typically lasts 30-40 minutes (with a small percentage of chases lasting up to about 80 minutes), encirclement lasts 30-60 minutes (with a very small percentage of encirclements lasting up to about 75 minutes), and length of confinement lasts another 40-60 minutes (with a small percentage lasting up to about 90 minutes) (Myrick & Perkins, 1995), so that time from initiation of chase to release typically ranges between about 1.5 and 2.5 hours (with a potential maximum in a few sets of about 4 hours). Once the dolphins perceive that the backdown channel is ready, they swim out quickly and continue their escape by swimming at even higher speeds (3-4 m/sec) for about 90 minutes before reverting to pre-chase behaviors (Chivers & Scott, 2002).…”

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confidence: 99%

Fishery Effects on Dolphins Targeted by Tuna Purse-seiners in the Eastern Tropical Pacific Ocean

Edwards¹

2007

International Journal of Comparative Psychology

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“…Furthermore, if purse-seine operations are breaking the strong mother-calf bond, disruption of other social bonds may also be occurring. These previously unrecognized unobserved calf deaths, the population consequences of social disruption, as well as the consequences of acute and chronic stress (Myrick andPerkins 1995, Curry 1999), will all need to be considered in a complete assessment of the effects of the fishery on the population dynamics of spotted and spinner dolphins in the ETP.…”

Section: Implications For Dolphin Stock Assessment and Managementmentioning

confidence: 99%

Unobserved Kill of Nursing Dolphin Calves in a Tuna Purse‐seine Fishery

Archer

Gerrodette

Dizon

et al. 2001

Marine Mammal Science

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The kill of dolphins (Stenella attenuata and S. longirostris) in the eastern tropical Pacific tuna purse‐seine fishery has been underestimated because of unobserved deaths of nursing calves due to separation from their mothers during fishing. Based on an analysis of dolphins killed from 1973 to 1990, and depending on the length at which calves are assumed to become independent, there was a deficit of calves relative to the number of lactating females killed in 24%–32% of 1,847 spotted‐dolphin sets and in 13%–19% of 563 spinner‐dolphin sets. We found a deficit of 0.31–0.45 spotted dolphin and 0.15–0.26 spinner dolphin calves per set. If these missing calves were added to the observed kill, it would represent an increase in the kill of 10%–15% for spotted dolphins and 6%–10% for spinner dolphins in the sets we examined. We did not attempt to estimate the actual number of unobserved calf deaths due to purse‐seine fishing on dolphins, either in the sets we examined or in all dolphin sets. The actual number of unobserved calf deaths is likely to be higher than the calf deficit we found. Separation of dolphin mothers from calves could occur at any of several points in the fishing process, but most of these would be invisible to us and not produce a calf deficit. Estimation of the actual number of unobserved calf deaths would require further information on how frequently permanent mother‐calf separations occur, the fraction of calves that survive after separation, the fraction of lactating females set upon that are carrying calves, and the fraction of calves killed that are actually related to lactating females killed in the same set. In any case, the observation of a calf deficit indicates that the reported dolphin kill fails to measure the full impact of purse‐seine fishing on spotted and spinner dolphin populations.

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Adrenocortical color darkness and correlates as indicators of continuous acute premortem stress in chased and purse-seine captured male dolphins

Cited by 13 publications

References 44 publications

Altered swimming gait and performance of dolphin mothers: implications for interactions with tuna purse-seine fisheries

Altered swimming gait and performance of dolphin mothers: implications for interactions with tuna purse-seine fisheries

Fishery Effects on Dolphins Targeted by Tuna Purse-seiners in the Eastern Tropical Pacific Ocean

Unobserved Kill of Nursing Dolphin Calves in a Tuna Purse‐seine Fishery

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