Live Sharks Research Articles

Physiological assessment of the effects of experimental capture and transport in Pacific spiny dogfish

Sharks are collected from the wild as live specimens for display in aquariums and use in research. The methods by which live sharks are captured and transported can be associated with sub-lethal physiological outcomes or even mortality, which requires evaluation to determine optimal collection and transport methods for a given species. The present study evaluated the primary (i.e., endocrine) and secondary (i.e., biochemical) stress responses and mortality in Pacific spiny dogfish ( Squalus suckleyi) following capture and subsequent transport between experimental rod-and-reel angling and longline fishing. Dogfish were resilient to transport following capture by either method, exhibiting no at-vessel mortality and 0.03% delayed mortality. Longline captured dogfish exhibited signs of primary (i.e., elevated corticosterone) and secondary (i.e., elevated plasma potassium, osmolality, glucose, and lactate; decreased blood pH) stress responses, whereas dogfish that experienced rod-and-reel capture and transport only exhibited a secondary stress response (i.e., elevated plasma potassium, osmolality, and lactate; decreased blood pH). Together, these data demonstrate that Pacific spiny dogfish are robust to capture and transport using experimental hook-and-line fishing techniques.

PENGATURAN PEMANFAATAN PERDAGANGAN JENIS IKAN DILINDUNGI/APPENDIKS CITES DI WILAYAH KERJA LPSPL SERANG

The Convention on International Trade in Endangered Species (CITES) of Wild Fauna and Flora which has been ratified through Presidential Decree No. 43 of 1978, is the nation's commitment to the conservation of endangered, endemic, and protected fish species. Trading traffic of protected fish species/CITES Appendix in of the Coastal Resources Management Regional Office (LPSPL) Serang working area is quite high, so it is necessary to control the utilization of protected fish species to maintain the sustainability of fish resources. The method of collecting data is through recording and direct interviews with service officers and treasurers of LPSPL Serang, as well as secondary data from service databases on traffic activities for protected fish species/CITES Appendix during Semester I (January-June) year 2022. Based on data collected, 53 domestic recommendation letters have been issued consisting of 30,909.80 kg of shark products, 104.50 kg of ray fins, 1,308 kg of sea cucumbers, and 12,009 pcs of soft coral and anemone; Foreign recommendation letters totaling 1,317 recommendations consisting of 2,335,464.01 kg of shark products and 283 live sharks, 468,387.55 kg of ray products and 21 live rays, 24,121.86 kg of sea cucumbers, and 295,408 pcs of soft coral and anemone; Documents for transport of fish species consisting of 28 documents consisting of 53,595 arowanas and 3,752.79 kg of shark and ray fins in the CITES Appendix; Letters of transport for tentengan fish types consisting of 228 documents of 359 arowanas. Total value of PNBP obtained is Rp 1,312,204,811.

Frequency Domain Transformations and CNNs to Predict Unlabeled Shark Behavior With GPS Data

This paper provides a comprehensive analysis of frequency domain transformations applied to convolutional neural networks (CNN) to model and predict unlabeled shark behavior in the open ocean with GPS position data. The frequency domain-based CNN networks are compared against the time domain CNN to contrast the two CNN architectures. The shark behavior data were obtained through two datasets where tri-axis accelerometer data were collected from live sharks. The first dataset was from the CSULB Shark Lab and consisted of labeled shark behavior into four shark behavioral categories. The second dataset used in this study was unlabeled and recorded from sharks in the open ocean and had GPS positioning data and depth data points. Findings show that the CNN architecture based on the frequency domain slightly outperforms time-based CNNs for classifying California horn shark behavior. Through spectral density analysis, prominent features are extracted and allow for distinguishing the shark behaviors.

An overview on elasmobranch release as a bycatch mitigation strategy

AbstractSharks and rays are among the most threatened vertebrates, mostly due to commercial fisheries. Data on incidental capture is sparse, but it is estimated that about 50% of reported global catches of elasmobranchs are from bycatch. Elasmobranchs are captured in a variety of fishing gear throughout the world. One promising strategy to minimize incidental catches is the release of live sharks and rays. However, so far, no critical analysis had been carried out to assess the importance of release as a measure to mitigate the impacts of bycatch. Results indicated that despite onboard releases being cited in Plans of Action (along ZEEs) and recommendations/regulations of Regional Fisheries Management Commissions (in international waters), this measure is treated as secondary and has voluntary adherence, which can significantly reduce its efficiency. Moreover, among the Best Fishing Practice Manuals currently available, although release is cited as a priority, most of them do not consider the dynamics of the location/fishing modality for which it was developed. A change on how release is perceived is needed to prioritize this conservation strategy, as well as its potential as a social tool to reduce the impacts of bycatch on sharks and rays.

Effects of delayed phlebotomy on plasma steroid hormone concentrations in two elasmobranch species

Measuring circulating concentrations of steroid hormones can be used as a method for determining reproductive maturity and cycles in elasmobranchs. However, it is unknown how long steroid hormones remain stable in elasmobranch blood following capture, and thus how quickly these samples should be collected for the results of subsequent steroid hormone analyses to be accurate. The objectives of this study were to determine if the sex steroid hormones progesterone, testosterone and estradiol would remain at stable concentrations in the blood of the Spiny Dogfish (Squalus acanthias Linnaeus, 1758) and the Atlantic Sharpnose Sharks (Rhizoprionodon terraenovae Richardson, 1836) that were captured, left on deck and un-refrigerated for 24 hr. Blood samples were serially drawn from five initially live sharks over a period of 24 hr. While concentrations of all three hormones did significantly fluctuate over the sampling period in both species, the resulting hormone concentrations from each sampling period still fell within the range of previously reported values for each species in their respective reproductive stage. Additionally, no significant changes in hematocrit were detected in either species over the 24-hr period. This research represents an extreme situation in which sharks were left on deck and un-refrigerated, and suggests that even when subjected to these conditions steroid hormone concentrations may fluctuate, but the resulting values may still be useful for assessing reproductive stage.

Sharks in the jungle: real and imagined sea monsters of the Maya

Abstract

Comparison of fin and muscle tissues for analysis of signature fatty acids in tropical euryhaline sharks

Fatty acid (FA) analysis can provide an effective, non-lethal method of elucidating the trophic ecology of fish. One method utilised in the field is to collect biopsied muscle tissue, but this can be problematic in live sharks due to a thick dermal layer with extensive connective tissue. The aim of this research was to determine whether fin and muscle tissue yield similar FA profiles in three species of tropical euryhaline sharks: Carcharhinus leucas, Glyphis garricki and Glyphis glyphis. Fatty acid profiles were detectable in fin clips as small as 20mg (~5mm×6mm) and muscle biopsies >10mg mass. Overall profiles in relative (%) FA composition varied significantly between fin and muscle tissues for C. leucas and G. garricki (global R-values=0.204 and 0.195, P<0.01), but not G. glyphis (global R-value=0.063, P=0.257). The main FAs that contributed to these differences were largely 18:0 for C. leucas, 20:4ω6 for G. garricki and 20:5ω3 for G. glyphis, which reflect the different physiological functions and turnover rates of the two tissues. Notably, no significant differences were detected between tissue types for the major classes of FAs and abundant dietary essential FAs. It was concluded that FA profiles from either fin clips or muscle tissue may be used to examine the trophic ecology of these tropical euryhaline sharks when focusing on dietary essential FAs. Given that some non-essential FAs were different, caution should be applied when comparing FA profiles across different tissue types.

A new metric for measuring condition in large predatory sharks.

A simple metric (span condition analysis; SCA) is presented for quantifying the condition of sharks based on four measurements of body girth relative to body length. Data on 104 live sharks from four species that vary in body form, behaviour and habitat use (Carcharhinus leucas, Carcharhinus limbatus, Ginglymostoma cirratum and Galeocerdo cuvier) are given. Condition shows similar levels of variability among individuals within each species. Carcharhinus leucas showed a positive relationship between condition and body size, whereas the other three species showed no relationship. There was little evidence for strong differences in condition between males and females, although more male sharks are needed for some species (e.g. G. cuvier) to verify this finding. SCA is potentially viable for other large marine or terrestrial animals that are captured live and then released.

Shark bycatch and mortality and hook bite-offs in pelagic longlines: Interactions between hook types and leader materials

This study addressed the influence of hook type (circle vs J-hook) and leader material (nylon vs wire) on longline catch and mortality rates of target and bycatch species in a pelagic longline fishery targeting swordfish, Xiphias gladius, and tunas. A total of 603 individuals (53% classified as bycatch) were caught on 17,000 hooks. Sharks constituted 45% of the bycatch. Bite-offs (i.e. missing hooks) corresponded to ∼33% of the shark catch and occurred mostly on nylon leaders (97%). Hook type had no significant effect on catchability or mortality of any species or groups. However, nylon leaders caught more bigeye tuna, Thunnus obesus and all target species combined, while wire leaders caught more blue shark, Prionace glauca and all sharks combined. If bite-offs were assumed to be undetected sharks, differences in shark catchability between leader types disappear. Moreover, significant differences in blue shark catch rate between leader types was found in J-hook treatments only. Higher proportions of live sharks were found on wire leaders. The catch and mortality rates of sharks in longline fisheries may be underestimated when monofilament leaders are used. This study highlights the need for understanding the role of every longline component in gear performance analysis.

Reducing the environmental impact of shark-control programs: a case study from KwaZulu-Natal, South Africa

Large-scale shark-control programs at popular beaches in New South Wales and Queensland, Australia, and KwaZulu-Natal (KZN), South Africa, provide protection against shark attack. Although these programs have enhanced bathing safety, reducing the environmental impacts of decades of fishing for large sharks and the associated by-catch remains a challenge. Over the past three decades, there have been several interventions to reduce such impact in the KZN program. The first was the release of all live sharks, including those species known to be responsible for fatal shark attacks. Measures to reduce catches of sharks associated with the winter influx of shoals of sardines, Sardinops sagax, have been increasingly successful. In addition, extensive removal of nets has resulted in a major reduction in effort. Collectively, these initiatives reduced mortalities of sharks by 64%. Baited lines, termed drumlines, were introduced at 18 beaches, where they replaced some of the nets. The former had a far lower by-catch of rays, turtles and cetaceans and significantly lower catches of certain shark species. Replacement of some nets with drumlines is planned for the remaining beaches. Only two attacks, both non-fatal, have occurred at protected beaches in KZN over the past three decades, indicating that the program has maintained its public safety mandate while it has succeeded in reducing its impact on the environment.

Demographic analyses of the dusky shark, Carcharhinus obscurus, in the Northwest Atlantic incorporating hooking mortality estimates and revised reproductive parameters

Demographic analyses were conducted for the dusky shark, Carcharhinus obscurus, in the Northwest Atlantic. Fishery-independent, fishery-dependent, and previously published data were used to estimate age specific by-catch mortality and reproductive cycle for incorporation into the analyses. Correspondence analyses were conducted for viability (dead or alive), shark length, month, soaktime, and region. Dead sharks were associated with small size, long soak times, and the spring season, while live sharks were associated with large size and shorter soak times. Data on reproduction suggested a 3-year reproductive cycle consisting of a 2-year gestation period and a 1-year resting period. Litter sizes ranged from 3–12 embryos. Decreasing age-specific fishing mortality and a 3-year reproductive cycle were used in age structured life tables which incorporated stochasticity in life history parameters through Monte Carlo simulation to estimate annual population growth. Demographic analyses showed that the dusky shark population would decline even at low levels of fishing mortality despite low natural mortality for neonates. The demographics of this species make it among the most vulnerable to excessive fishing mortality, and suggest stringent regulatory measures may be required to recover collapsed populations.

International shark fin markets and shark management: an integrated market preference–cohort analysis of the blacktip shark ( Carcharhinus limbatus)

The increasing demand for shark fins in Asia, and the publicity resulting from finning and discarding live sharks, has generated concern regarding the sustainability of the world's shark populations. These concerns can be attributed to the shark's life history, which is characterized by a pattern of slow growth, late maturity, few offspring, and long life, making populations vulnerable to overexploitation. Once overexploited, shark stocks will be slow to recover due to these constraints. Despite an increase in consumption and trade of shark fins and other shark products, and the vulnerability of shark populations once overexploited, little effort has been expended to understand the biology and economics of sharks and shark fisheries until recently. This study adds to the understanding of linkages between shark product markets, specifically shark fins, and the biology of shark populations by explicitly incorporating multi-attribute market information into bioeconomic modeling. Results from conjoint analysis of the Hong Kong dried, processed end-user markets is incorporated into a blacktip shark ( Carcharhinus limbatus) cohort model to estimate the optimal harvest size and age that maximize economic value. Results show that optimal harvest sizes and ages for all mortality and discount factor scenarios are greater than the maturation sizes and ages for both male and female blacktip. Policy implications for this study are also discussed.

Threatened Fishes of the World: Carcharias taurus (Rafinesque, 1810) (Odontaspididae)

Threatened Fishes of the World: Carcharias taurus (Rafinesque, 1810) (Odontaspididae)