Capture Stress Research Articles

Cognition and animal welfare.

Animals exhibit species-typical adaptations of behavior and may suffer stress in captivity if they are prevented from performing these patterns of behavior. This article considers whether these particular 'needs' rely on cognitive processes or are performed without complex cognition despite their appearance of behavioral complexity. Emotion and cognition in animals are also discussed, particularly whether animals can feel emotions and, if so, what ranges of emotions they might feel. Cognitive capacities that would contribute to suffering include empathy with the suffering of others, memories of negative events and suffering in anticipation of future events. Cognitive bias of individual animals toward positive or negative feelings is related to dominance of the left or right hemisphere, respectively. These biases might be reflected in the animal's preferred limb to pick up food. Hence, limb preference could be a useful measure of cognitive bias. Post-traumatic stress disorder is a cognitive condition that, it is suggested, might involve dominance of the right hemisphere. This debilitating condition is experience-dependent and not infrequently seen in animals in captivity. In conclusion, it is argued that there is an obvious need for more research on cognition as it relates to animal welfare and as a basis for changing legislature to protect animals from suffering. Copyright © 2010 John Wiley & Sons, Ltd. For further resources related to this article, please visit the WIREs website.

Effects of capture stress on free-ranging, reproductively active male Weddell seals

Physiological stress responses to capture may be an indicator of welfare challenges induced by animal handling. Simultaneously, blood chemistry changes induced by stress responses may confound experimental design by interacting with the biological parameters being measured. Cortisol elevation is a common indicator of stress responses in mammals and reproductive condition can profoundly influence endocrine response. We measured changes in blood cortisol and testosterone induced by handling reproductively active male Weddell seals (Leptonychotes weddellii) early and late in the breeding season. Weddell seals have the highest resting cortisol levels of all mammals yet showed a clear, prolonged elevation in cortisol in response to capture. Responses were similar when first caught and when caught a second time, later in the breeding season. Baseline testosterone levels declined over the breeding season but were not altered by capture. Administering a light dose of diazepam significantly ameliorated the cortisol response of handled animals without affecting testosterone levels. This may be an effective way of reducing acute capture stress responses. Male breeding success in years males were handled was no different to the years they were not, despite the acute capture response, suggesting no long-term impact of handling on male reproductive output.

Effects of reproductive stage, GH, and 11-ketotestosterone on expression of growth differentiation factor-9 in the ovary of the eel, Anguilla australis

In order to study the regulation of the growth differentiation factor-9 (gdf9) gene in a primitive teleost with semelparous life history, we cloned a cDNA encoding shortfinned eel Gdf9, expressed a partial peptide in Escherichia coli, and raised an antiserum to evaluate changes in Gdf9 expression during its pituitary homogenate-induced reproductive cycle. The effects of in vivo and in vitro exposure to the androgen 11-ketotestosterone (11-KT), known to affect previtellogenic (PV) oocyte growth, were also determined. Furthermore, we investigated whether Gdf9 expression was metabolically gated by treating PV fish with recombinant GH in vivo. Immunoreactive proteins of ca. 52 and 55 kDa were identified by western blot analysis. Gdf9 message and protein were most abundant in PV oocytes, and peaked slightly earlier for mRNA than for protein. Captivity resulted in reduced gdf9 mRNA levels, which were restored following pituitary homogenate treatment. As oocytes progressed through induced oogenesis, Gdf9 expression decreased. Neither 11-KT nor GH treatment affected gdf9 mRNA levels in PV fish, although GH could partially restore handling- or captivity-induced decreases in gdf9 mRNA levels. Semelparous eels thus show an expression pattern of Gdf9 during oogenesis that is similar to that seen in other vertebrates, that appears responsive to handling or captivity stress, and whose control remains to be elucidated.

Urinary corticosterone metabolite responses to capture, and annual patterns of urinary corticosterone in wild and captive endangered Fijian ground frogs (Platymantis vitiana)

This study was based on the development of a non-invasive glucocorticoid enzyme-immunoassay for the assessment of stress in wild and captive endangered Fijian ground frogs (Platymantis vitiana). Enzyme-immunoassays were developed and validated for the first time to non-invasively measure both cortisol and corticosterone metabolites in frog urine. Frog urine showed parallel displacement with corticosterone but not cortisol standards, therefore corticosterone enzyme immunoassays were used to examine stress in wild and captive frogs. Urinary corticosterone metabolite concentrations increased in frog urine (n = 4) at 6 h, 1 day and 2 days after injection with adrenocorticotropic hormone (0.44 μg g–1 bodyweight), indicating that the corticosterone enzyme-immunoassay could detect changes in circulating corticosterone in frogs. Urinary concentrations of corticosterone were measured in wild frogs (n = 18) after capture in the field. The first measurement beyond the initial sample was at 2–3 h. Mean urinary corticosterone concentrations rose after the initial sample and were significantly elevated in samples collected 3–4 h after capture. This is the first demonstration of a urinary corticosterone response to capture in amphibians. Urinary corticosterone metabolite concentrations for all months combined were lower in captive males than in wild males, and differed between vitellogenic, non-vitellogenic and captive females. Concentrations did not differ between captive and wild females. In conclusion, urinary corticosterone enzyme immunoassays can be used in frogs for assessing stress responses to capture and natural stress profiles of both captive and wild populations.

Sublethal effects of catch-and-release fishing: measuring capture stress, fish impairment, and predation risk using a condition index

Abstract Campbell, M. D., Patino, R., Tolan, J., Strauss, R., and Diamond, S. L. 2010. Sublethal effects of catch-and-release fishing: measuring capture stress, fish impairment, and predation risk using a condition index. – ICES Journal of Marine Science, 67: 513–521. The sublethal effects of simulated capture of red snapper (Lutjanus campechanus) were analysed using physiological responses, condition indexing, and performance variables. Simulated catch-and-release fishing included combinations of depth of capture and thermocline exposure reflective of environmental conditions experienced in the Gulf of Mexico. Frequency of occurrence of barotrauma and lack of reflex response exhibited considerable individual variation. When combined into a single condition or impairment index, individual variation was reduced, and impairment showed significant increases as depth increased and with the addition of thermocline exposure. Performance variables, such as burst swimming speed (BSS) and simulated predator approach distance (AD), were also significantly different by depth. BSSs and predator ADs decreased with increasing depth, were lowest immediately after release, and were affected for up to 15 min, with longer recovery times required as depth increased. The impairment score developed was positively correlated with cortisol concentration and negatively correlated with both BSS and simulated predator AD. The impairment index proved to be an efficient method to estimate the overall impairment of red snapper in the laboratory simulations of capture and shows promise for use in field conditions, to estimate release mortality and vulnerability to predation.

Two Unsuccessful Reintroduction Attempts of Rock Hyraxes (Procavia capensis) into a Reserve in the KwaZulu-Natal Province, South Africa

Rock hyraxes (Procavia capensis) are categorized as ‘Least Concern’ in the 2008 IUCN Red List of Threatened Species. In South Africa they were once listed as vermin in the old Cape Province due to their high population numbers and Impact on grazing. However, about 10 years ago, populations in the KwaZulu-Natal province became locally extinct. This resulted in the recent reintroductions of rock hyraxes, purchased at annual wildlife auctions in the province. Success of these reintroductions was unknown as there had been no post-release monitoring. This study determined the success of reintroducing rock hyraxes, using two source populations, namely rock hyraxes that had been in captivity for 16 months (n = 17) and those from the wild (n = 9). Captive rock hyraxes did not have site fidelity after release and after three months could not be found. All wild rock hyraxes, except one whose fate is unknown, were found dead within 18 days of release. One had an accidental death while the rest were preyed upon. In conclusion, the reintroduction of captive and wild rock hyraxes likely failed due to predation. This may have been a consequence of group disintegration, probably as a result of incorrect group composition, captive stress, and type of release. Suggestions to improve the success of future rock hyrax reintroductions are provided.

Seasonal variation in hormonal responses of timber rattlesnakes (Crotalus horridus) to reproductive and environmental stressors

Data addressing adrenocortical modulation across taxonomic groups are limited, especially with regard to how female reproductive condition influences the sensitivity of the hypothalamus-pituitary-adrenal axis. We investigated seasonal and reproductive variation in basal and stress-induced hormone profiles in a population of free-ranging timber rattlesnakes (Crotalus horridus) in north-central Pennsylvania during spring (i.e., May), summer (i.e., July), and early fall (i.e., September). Baseline corticosterone concentrations varied seasonally and were significantly lower during the summer sampling period in July. We observed a significant negative relationship between baseline corticosterone and testosterone in male snakes, while baseline corticosterone and estradiol tended to be positively correlated in females. Treatment of snakes with 1 h of capture stress significantly increased corticosterone across all seasons. However, there was a significant interaction between corticosterone responses to capture stress and season, suggesting that adrenocortical function is modulated seasonally. Because elevated corticosterone may be associated with reproduction, we asked whether hormonal stress responses vary with female reproductive condition. Although sample sizes are low, reproductive snakes had significantly higher baseline and stress-induced corticosterone concentrations than non-reproductive or post-parturient females. Further, despite similar baseline corticosterone concentrations between non-reproductive and post-parturient rattlesnakes, post-parturient females responded to capture stress with a significantly higher increase in corticosterone. Collectively, these data suggest that the sensitivity of the hypothalamus-pituitary-adrenal axis varies both seasonally and with changing reproductive states.

Plasma Corticosterone Levels of Semipalmated Sandpiper Calidris pusilla Overwintering in a Tropical Coastal Lagoon of Northeastern Venezuela

Semipalmated sandpiper Calidris pusilla arrives on the coasts of Venezuela between the middle of August and early September, staying there until May when birds prepare for vernal migration. To investigate possible relationships between corticosterone levels and body mass changes during preparation for migration, we sampled birds during wintering (January) and vernal premigration (May) over 2 years. Body mass and fat increased significantly from wintering to vernal premigration in both years. Capture stress levels of corticosterone varied between 30 and 150 ng mL(-1), the highest being during wintering. These results strongly suggest that increase in body mass of C. pusilla during preparation for vernal migration in a tropical environment was promoted by a decreased corticosterone secretion response to stress.

Evaluating capture stress and its effects on reproductive success in Svalbard reindeer

Although many ecological studies of wild animal populations rely on capturing individuals at least once, few have investigated either the immediate stress responses of capture, restraint, and handling, or the longer term consequences on reproductive success. In this paper, we assume that the degree of stress increase with the time taken to capture and process an animal prior to release. The influence of time since onset of capture on body temperature and blood chemistry indicators of stress was investigated in 137 adult female Svalbard reindeer ( Rangifer tarandus platyrhynchus Vrolik, 1829) and 63 calves of both sexes captured by net in late-winter 2004 and 2005. In addition, we looked for evidence of negative effects of capture stress on reproductive success in marked animals over the period from 1995 to 2006. Body temperature increased with both chase time and the time the animals were restrained. In the latter case, body temperature increased twice as fast in nonpregnant animals (0.13 °C/min) compared with pregnant animals. Cortisol, glutamate dehydrogenase, and γ-glutamyltransferase all increased with time from onset of capture. However, the relationship for glucose with time since onset of capture increased initially before declining again. We found no evidence of a lower calving success in animals captured the previous winter when compared with animals that had not been captured the previous winter. Likewise, there was no relationship between the strength of the acute stress response (measured as cortisol concentrations) and the probability of pregnant females having a calf at foot the subsequent summer.

Decreases in Shark Catches and Mortality in the Hawaii‐Based Longline Fishery as Documented by Fishery Observers

AbstractThis article summarizes catch data for sharks collected by fishery observers during two periods (1995–2000 and 2004–2006) in the Hawaii‐based pelagic longline fishery, which targets swordfish Xiphias gladius in the shallow‐set sector and bigeye tuna Thunnus obesus in the deep‐set sector. The blue shark Prionace glauca was the predominant shark species caught throughout the study period (84.5% of all sharks). Five other species (bigeye thresher Alopias superciliosus, oceanic whitetip shark Carcharhinus longimanus, shortfin mako Isurus oxyrinchus, silky shark C. falciformis, and crocodile shark Pseudocarcharias kamoharai) were relatively common (1.0–4.1%). Two major developments affected shark catches in this fishery during the study period. The first was the prohibition in 2000 of shark finning under most circumstances. The second development was that management measures were taken in 2000 and 2001 to protect sea turtles (leatherback sea turtles Dermochelys coriacea and loggerhead sea turtles Caretta caretta) and these measures included a closure of the shallow‐set (swordfish‐targeting) sector for more than 3 years. The closure caused decreases in shark catches because the shallow‐set sector was typically characterized by high catch rates. The shallow‐set sector was reopened in 2004. Comparisons of nominal catch per unit effort (number of sharks/1,000 hooks) revealed significant differences in catch rates between the two fishery sectors and the two periods. Blue shark and shortfin mako catch rates were significantly greater in the shallow‐set sector than in the deep‐set sector of the fishery, whereas the opposite was true for the deeper‐dwelling bigeye threshers and crocodile sharks. Catch rates for the blue shark, oceanic whitetip shark, bigeye thresher, and crocodile shark were significantly lower in 2004–2006 than in 1995–2000. For the blue shark in particular, the combination of reduced catch rates, the finning ban, and an apparent capacity to resist the stress of capture on longline gear resulted in low (4%–5.7%) minimum mortality estimates. Therefore, we conclude that the Hawaii‐based pelagic longline fishery has made substantial progress in reducing shark mortality.

Mortalities Associated with Sepsis, Parasitism, and Disseminated Round Cell Neoplasia in Yellow-Lipped Sea Kraits (Laticauda colubrina)

This case series describes multiple mortalities associated with sepsis, neoplasia, and endoparasitism in yellow-lipped sea kraits (Laticauda colubrina) at an exhibit aquarium. Over a 2-yr period, the facility kept 42 L colubrina, of which 38 died and 19 were suitable for necropsy and histopathology. The common clinical syndrome seen in these animals consisted of partial to compete anorexia, increased time spent "hauled-out" on land, intermittent regurgitation, chronic lethargy, and weight loss. Few animals died without premonitory signs. Nutritional support and treatment for presumptive parasitism and sepsis were unsuccessful. The mortality seen in this collection of sea kraits could be placed into three groups; one group of animals (n=9) died of sepsis secondary to necrotizing enteritis or pneumonia; one group (n=6) remained apparently healthy for over 1 yr and then died with multifocal granulomas and sepsis; and the last group (n=3) died as a result of multicentric lymphoid neoplasia with secondary sepsis. The unifying factor in the majority of these cases is the presence of septicemia as the proximate cause of death. Based on the clinical picture, it is presumed that an immunosuppressive event, such as transport, captivity stress, or possible concurrent viral infection, resulted in a septic event and death.

SUBCUTANEOUS ABSCESS DUE TO PSEUDOMONAS AERUGINOSA IN CAPTIVE ASP VIPER ( VIPERA ASPIS )

SUMMARY Abscesses are one of the most frequent clinical ent ities of the captive snakes (Hoppmann and Wilson Barron, 2006). In contrast with the mammals, the reptilian purulent material is caseous, forming hard “cheese-like” plu gs that are nearly impenetrable to antibiotics, making the key to successful treatment of the reptilian abscesses the complete removal of the abscess cavity and surrounding fibro us capsule (Mader, 2006). Many causes are found for abscesses; foreign bodies embedded, p arasites (Mihalca et al., 2007), fungi and bacteria (Kobolkuti and Czirjak, unpublished data) can lead to the formation of the exudates. Bacteria from the genus Pseudomonas are part of the normal flora of the oral cavity and intestinal tracts of the snakes (Blaylock, 2001; Ko bolkuti and Czirjak, unpublished data). Often they are considered opportunistic pathogens, causing different clinical diseases under the stress of the captivity. A case of subcutaneous abscess was described at a c aptive asp viper ( Vipera aspis ). During the examination, the snake showed a well localized 3 cm x 1 cm abscess with a central stub-like scar. After the local anesthesia, all the parts of the abscess were surgically removed. Pseudomonas aeruginosa was isolated in monoculture from the pus and ident ified as casual agent of infection . Based on antibiograme we started a treatment using Enrofloxacin generally (10mg/kgc i.m.). After 5 days of antibiotic and pos t-surgical treatment, the recovery of the animal was 100%. To our knowledge this is the first described case o f Pseudomonas infection in captive asp viper ( Vipera aspis ).

Comparison of Hematological Stress Indicators in Recently Captured and Captive Paedomorphic Mole Salamanders, Ambystoma talpoideum

Abstract Measuring stress in animals is an important component of many research studies, and it has traditionally been performed via sampling levels of corticosterone in plasma. A secondary, “hematological” approach used most commonly by researchers of birds, mammals, and other taxa involves evaluating leukocyte profiles from blood smears. Such research has shown that leukocytes have a characteristic response to stress, although in amphibians this phenomenon is not as well studied. In general, stress can induce a rise in the ratio of neutrophils to lymphocytes. We evaluated the hematological response of paedomorphic Mole Salamanders (Ambystoma talpoideum) to captivity stress, specifically focusing on this parameter, but also examining other white blood cell types. Individuals captured in the wild and held in captivity for ten days before sampling had significantly more neutrophils, fewer lymphocytes, and higher ratios of neutrophils to lymphocytes than those captured from the same locations and sampled wi...

Stress, Metabolism, and Antioxidants in Two Wild Passerine Bird Species

Antioxidants protect against free-radical damage, and free radicals, in turn, are thought to underlie aging. Thus, measuring antioxidants may aid field ecologists in understanding the physiological mechanisms that underlie life-history trade-offs. Antioxidant levels are known to vary markedly in response to the stress of capture in many birds. These changes in antioxidants could result from regulation (e.g., by stress-related hormones) or consumption (e.g., by an increase in free radicals due to increased metabolic rate). Here we experimentally test the effect of increased metabolic rate on circulating antioxidant and corticosterone concentrations in two wild passerine bird species, house sparrows (Passer domesticus) and gray catbirds (Dumetella carolinensis). We increased metabolic rate via exposure to low ambient temperatures overnight in captivity and measured circulating antioxidant capacity, uric acid, corticosterone, and oxygen consumption in cold-exposed and control individuals. Both species showed increases rather than decreases in all antioxidant parameters overnight, contradicting a consumption-by-energy-expenditure hypothesis. Both positive and negative correlations between antioxidant response and corticosterone response were occasionally but not consistently present, refuting a generalized regulation-by-corticosterone hypothesis. High baseline uric acid predicted diminished response of corticosterone and all antioxidants. Thus, high uric acid may reflect recent stress, poor condition, or a compensatory response. Relationships among metabolic rate, antioxidants, and corticosterone differed qualitatively between the species.

Proliferative visceral Isospora (atoxoplasmosis) with morbid impact on the Israeli sparrow Passer domesticus biblicus Hartert, 1904

House sparrows (Passer domesticus biblicus Hartert, 1904) caught in the Jordan valley, the coastal plain, and the desert region in Southern Israel were found massively infected with extraintestinal proliferative stages of Isospora, previously named Atoxoplasma. Infection coincided with Isospora spp. infections in the digestive tract. Prevalence of infection reached 70% among sparrows of all three regions; however, only in the Jordan valley did the severity of the sparrows compromised their survival. Healthy appearing captured birds showed symptoms of "going light" syndrome -- diarrhea, emaciation, and death. Birds succumbed within 48 h to 15 days after confinement to cages. Merozoites accumulated predominantly in the spleen but were rarely found in the peripheral blood. The parasite stages in the visceral leukocytes propagated by merogony and yielded single large waiting-stage merozoites. Visceral infections resulted in multifocal necrosis. Proliferative visceral Isospora infection (atoxoplasmosis) is one of the more severe causes of mortality among captive birds, free-ranging birds appear to coexist with the infection but succumb under capture stress.

Effets de l’acéturate de diminazène et de l’hydrochlorure de mélarsamine sur les modifications des paramètres biochimiques chez des gazelles au front rouge (<em>Gazella rufifrons</em>) expérimentalement infectées avec <em>Trypanosoma brucei</em>

Une étude a été menée pour déterminer les effets chémothérapeutiques de l’hydrochlorure de mélarsamine (Cymelarsan®) et de l’acéturate de diminazène (Bérénil®) sur les paramètres biochimiques sanguins chez des gazelles au front rouge expérimentalement infectées par Trypanosoma brucei. Suite à la parasitémie des gazelles, les observations suivantes ont été faites : une augmentation significative (p < 0,05) de cortisol sérique, de l’alanine aminotransférase, de l’aspartate aminotransférase, de la bilirubine totale, de la créatinine, de l’urée, de l’acide urique et des lipides totaux, ainsi qu’une baisse significative des protéines sériques totales, du niveau de l’albumine et du glucose. En revanche, l’activité de la phosphatase d’alcaline a fluctué autour des valeurs normales (p > 0,05). Ces modifications biochimiques sont revenues à des valeurs proches de celles de la période de préinfection avant la fin de l’expérience chez les gazelles traitées avec 0,3 ou 0,6 mg/kg de poids vif (PV) de Cymelarsan ou 7,0 mg/kg de Bérénil. Les résultats semblent indiquer qu’un stress initial, associé à une augmentation du niveau du cortisol sérique et à son effet immunodépresseur pouvaient être responsable de l’installation et de l’expression clinique de l’infection chez les gazelles au front rouge. Par ailleurs, la sévérité des effets biochimiques produits expérimentalement a montré que la trypanotolérance chez les gazelles sauvages pouvait être compromise, surtout lorsque ces dernières étaient exposées au stress de la captivité. Les résultats ont aussi montré que le Cymelarsan à 0,3 ou 0,6 mg/kg PV et le Bérénil à 7,0 mg/kg PV étaient efficaces pour contrôler la maladie dans les conditions de l’expérience.

Collaborative studies and animal reuse

Toby Pfeiffer, PhD, was well known for her contributions to the field of learnedhelplessness and its relationship to prisoner-of-war captivity stress in humans. She used squirrel monkeys formuchof her research,subjecting them tomild but frequent electrical shocks, such as 0.75 milliamps for 30 s, repeated 20 times in 1 hour. She justified her methodology to the IACUCbynoting that shehad subjectedherself to the same shock intensity and duration and had felt only moderate pain. She said that the monkeys also appeared to have experienced onlymoderate discomfort, as evidenced by the shifting of their position and related evasivemovements,butnovocalizations or other indicators of severe pain. Furthermore, she presented data showing that cortisol levels in shockedmonkeys were only slightly higher than those in unshocked control monkeys. These statements were typically included in all of Pfeiffer’s protocol applications.Her studies includedbehavioral tests followed by euthanasia and subsequent brain structural and biochemical analyses. Pfeiffer’s most recent protocol submission was somewhat different. She planned to use a modified animal shock protocol (fewer repetitions) and then carry out her behavioral testing. Instead of euthanizing the monkeys, however, she proposed sending them to a nearby colleague who would carry out multiple physiological samplings (metabolomics) with equipment available only in his laboratory.As part of his work he would reshock the animals, using the same methodology used by Pfeiffer. Pfeiffer’s protocol went into great detail about the science behind both studies, the methods of transporting the animals, the means of accounting for shipping andother stressors, the need for approval by the receiving university’s IACUC and many other details. Initially, this seemed somewhat reasonable to the IACUC, but after a discussion with Pfeiffer, the committee became firm in its contention that the two studies were independent and could be done with two groups of squirrel monkeys, not just Pfeiffer’s. The committee decided that it was inappropriate to subject the animals a second time to the inescapable electrical shocks. In otherwords, the IACUC concluded that the reuse of the animals was

Annual pattern of fecal corticoid excretion in captive Red-tailed parrots (Amazona brasiliensis)

Annual patterns of fecal corticoid excretion were analyzed in the threatened Red-tailed parrot (Amazona brasiliensis) in captivity. Corticoid concentration over the 15 months of the study (mean +/- standard error, 12.6 +/- 0.32 ng g(-1), n = 585) was lowest around May (the southern Fall), and greatest around September (late winter), just prior to their normal breeding period. Corticoid excretion follows a seasonal pattern best explained by reproductive cycles rather than climate, although climate may be involved in the timing of corticoid excretion. Fecal corticoids also show promise as a tool to measure stress levels. We demonstrate that fecal corticoid measurement is a simple, yet efficient method for monitoring adrenocortical activity in captive, and perhaps wild, parrots. Monitoring adrenocortical activity can inform researchers about imposed stress in captivity, whether pair-bonds are forming in captive birds, and of the timing of breeding both in captivity and in nature.

The Use of Animal-Borne Imaging to Assess Post-Release Behavior as it Relates to Capture Stress in Grey Reef Sharks, Carcharhinus amblyrhynchos

Sharks are subjected to extensive commercial and recreational fisheries worldwide. Current management, which imposes bag limits, minimum sizes, and quotas, mandates the release of large numbers of sharks each year, but little is known of post-release behavior and survivorship. Using animal-borne imaging technology, we examined the effects of handline capture on post-release behavior of six grey reef sharks, Carcharhinus amblyrhynchos, at Johnston Atoll (Central Pacific) as it relates to physical trauma and physiological stress induced by capture. To quantify the extent of physical trauma, 25 grey reef sharks (including these six), ranging from 56–135 cm fork length, were examined for evidence of external tissue damage after 2.0–12.8 minutes of handline capture. In addition, these fish were blood sampled to quantify relative changes in acid-base biochemistry. Although blood lactate increased and blood bicarbonate decreased significantly relative to the duration of the capture event, blood pH did not drop significantly and there was no evidence of respiratory or metabolic acidoses. Post-release behavior, as evidenced by animal-borne imaging, included group (n=3) and solitary (n=2) activities that had been previously described in this species. A single shark exhibited aberrant behavior, which included a two-minute period of disorientation, lack of movement, and loss of equilibrium; this behavior was attributed to extensive physical trauma associated with hook damage. When coupled with quantified information relative to the capture event, we found that animal-borne imaging is a useful tool for collecting direct observations of post-release behavior in sharks so that fishery managers and researchers can better assess the impacts of various capture techniques.

Sex, seasonal, and stress-related variations in elasmobranch corticosterone concentrations

Serum corticosterone was previously studied in numerous elasmobranch fishes (sharks, skates and rays), but the role of this steroid, widespread throughout many taxa, has yet to be defined. The goal of this study was to test whether corticosterone varied in response to acute and chronic capture stress, and across the reproductive cycle in the bonnethead shark, Sphyrna tiburo, and Atlantic stingray, Dasyatis sabina. Serum corticosterone in S. tiburo increased following capture and again 24 h post-capture, possibly caused by interference with 1α-hydroxycorticosterone, the primary stress hormone in elasmobranchs. Higher serum concentrations in males compared to females were observed in both species. Variations in corticosterone also occurred during the reproductive cycle in both species. Consistent with other taxa, elevations in male bonnethead sharks and stingrays coincided with peak testicular development and mating. Elevations in female bonnethead sharks occurred from the time of mating through sperm storage into early gestation. In contrast, corticosterone levels in female stingrays were low during their protracted mating season, but elevated through late gestation and parturition. These results indicate that corticosterone has a limited role, if any, in acute and chronic stress associated with capture in S. tiburo, but likely has physiological functions associated with its glucocorticoid properties across the reproductive cycle of both species.