Mustelus Henlei Research Articles

Sharkaeology: Expanding Understandings of Historical Chinese Diaspora Shark Fisheries in Monterey Bay, California, through the Genetic Species Identification of Archaeological Chondrichthyes Remains

Prior to burning down in 1906 CE, Point Alones in the Monterey Bay region of Central California was home to one of the largest Chinese fishing communities in the United States of America. Both historical records and the recovery of numerous cartilaginous fish (Chondrichthyes) vertebrae during archaeological excavations of the village indicate sharks were among the taxonomic groups being regularly harvested by its inhabitants. However, as shark vertebrae are difficult to identify past the family-level using conventional morphology-based approaches, our understanding of the Point Alones shark fishery remains incomplete. In this study, we address this issue by using ancient DNA analysis to assign species-level identifications to a sample of 54 shark vertebrae from the site. We successfully amplified a 173 bp fragment of the mitochondrial cytochrome c oxidase I gene from 47 of the 54 analyzed specimens (87.03%). Our results indicate that Tope Shark (Galeorhinus galeus; n = 39) was the primary focus of the site’s shark fishery, with Brown Smooth-Hound (Mustelus henlei; n = 7) and Leopard Shark (Triakis semifasciata; n = 1) also harvested to a lesser extent. All three of these species are found locally in the waters overlying the continental shelf, suggesting Chinese fishers were harvesting sharks from these coastal environments. While some of the sharks caught by fishers from Point Alones were likely being consumed at the village, historical records suggest a significant number of fins from harvested Tope Sharks were also likely being exported to China and other diaspora communities.

Ontogenetic morphometry of the brown smoothhound shark Mustelus henlei with implications for ecology and evolution.

The central tenet of ecomorphology links ecological and morphological variation through the process of selection. Traditionally used to rationalise morphological differences between taxa, an ecomorphological approach is increasingly being utilised to study morphological differences expressed through ontogeny. Elasmobranchii (sharks, rays and skates) is one clade in which such ontogenetic shifts in body form have been reported. Such studies are limited to a relatively small proportion of total elasmobranch ecological and morphological diversity, and questions remain regarding the extent to which ecological selection are driving observed morphometric trends. In this study, we report ontogenetic growth trajectories obtained via traditional linear morphometrics from a large data set of the brown smoothhound shark (Mustelus henlei). We consider various morphological structures including the caudal, dorsal and pectoral fins, as well as several girth measurements. We use an ecomorphological approach to infer the broad ecological characteristics of this population and refine understanding of the selective forces underlying the evolution of specific morphological structures. We suggest that observed scaling trends in M. henlei are inconsistent with migratory behaviour, but do not contradict a putative trophic niche shift. We also highlight the role of predation pressure and sex-based ecological differences in driving observed trends in morphometry, a factor which has previously been neglected when considering the evolution of body form in sharks.

Trophic structure and biomagnification of cadmium, mercury and selenium in brown smooth hound shark (Mustelus henlei) within a trophic web

Stable isotopic values of carbon (δ13C) and nitrogen (δ15N) were used to characterize the trophic structure and biomagnification of Cadmium (Cd), Mercury (Hg) and Selenium (Se) in a trophic web of 18 taxa namely zooplankton, crustaceans, mollusks, fishes, and Mustelus henlei shark collected off the western coast of Baja California Sur, Mexico. Isotopic results indicated interspecies variations in the trophic web structure with mean δ13C values of – 20.0‰ (zooplankton) < − 18.2 ‰ (M. henlei) < − 14.1 ‰ (Thaisella kiosquiformis, mollusk). In general, δ15N and δ13C values increased from primary consumers (zooplankton) to predators, following the isotopic patterns of other trophic webs. The concentrations of Cd, Hg and Se were relatively less in most of the organisms except mollusks that presented high concentrations of Cd. The biomagnification factors of the trophic web showed biodilution of Cd (Food Web Magnification Factor, FWMFCd = 0.2), biomagnification of Hg (FWMFHg = 3.34) and Se (FWMFSe = 1.45) respectively. However, the concentrations of Se did not increase consistently from the lower trophic levels to the higher ones. This study documents the dynamics of a marine trophic structure and demonstrates that biodilution/biomagnification processes of metal contaminants are largely species specific and are closely related to physical - chemical and food web structure.

Mercury maternal transfer in two placental sharks and a yolk-sac ray from Baja California Sur, Mexico

Total mercury (THg) concentrations were measured in muscle and liver of two placental viviparous sharks, the Pacific sharpnose shark (Rhizoprionodon longurio) and the brown smooth-hound (Mustelus henlei); as well as in the muscle, liver, and yolk of the yolk-sac viviparous speckled guitarfish (Pseudobatos glaucostigmus) in Baja California Sur. The aim was to determine which factors could be involved in maternal transfer and resultant maternal and embryonic THg concentration. Higher THg concentrations were found in pregnant females compared to embryos paired tissues. THg concentrations of embryo tissues decreased with total length (TL), except for the muscle of the Pacific sharpnose shark. THg concentrations of embryo muscle was positively related to THg concentration in the muscle of pregnant females. Embryos TL, muscle THg concentration of pregnant females, percentage of THg concentration in embryos, along with the reproductive strategy are relevant factors required to improve our understanding of THg concentration in embryo tissues.

Regional variation in multiple paternity in the brown smooth‐hound shark Mustelus henlei from the northeastern Pacific

Multiple paternity (MP) in the brown smooth-hound shark (Mustelus henlei) was assessed in 15 litters (15 mothers and 97 embryos) collected in the northern Gulf of California of which 86.7% were sired by more than one male (i.e., from 2 to 4 sires). When taken together with results from previous studies, this record indicates that there is regional variation in MP in M. henlei in the northeastern Pacific. This pattern is associated with variations in the reproductive traits of each population (e.g., female size and litter size). In the Gulf of California, the results of a generalized linear model (GLZ) indicated that the litters of larger females had a higher probability of MP compared to those of smaller females.

Global assessment of shark strandings

AbstractMarine wildlife stranding is a global phenomenon, and for some taxonomic groups, these events are well monitored and documented. Although sharks are among the most threatened vertebrates, strandings have historically been neglected, with little information on this topic currently available. To address this knowledge gap, a systematic review on scientific publications from indexed databases, multimedia material and citizen science databases was performed. A total of 3150 reports were recovered, with strandings dating back to 1880 including 89 species of sharks from 22 families. Both single/small‐scale and mass stranding events were observed. Species ranged from coastal to oceanic, with reports for small‐, medium‐ and large‐sized sharks. Leopard (Triakis semifasciata, Triakidae), brown smooth‐hound (Mustelus henlei, Triakidae) and salmon sharks (Lamna ditropis, Laminidae) were the species with most records. Females stranded significantly more than males, but juveniles and adults were affected in the same proportion. Shark strandings were reported for 47 countries, and the United States was the most representative location, highlighting the states of California and Oregon. Survival rates were extremely low, indicating that stranded sharks are more vulnerable that other taxonomic groups. Potential and putative causes were identified, being similar to those suggested for marine mammal strandings. Our results indicate that although they occur to a lesser extent when compared to mammals, shark strandings are neglected, and urgent measurements are necessary to better understand, document and to properly respond to these events.

Species-Specific Nuclear Genetic Markers for the Detection of Hybridization between the Grey Smoothhound (Mustelus californicus) and the Brown Smoothhound (Mustelus henlei)

Many species retain the physiological capacity to hybridize over long periods of evolutionary time. Hybridization has been reported for sharks and may be the reason for uncertainty regarding phylogenetic relationships within the genus Mustelus. Because of similar life histories and morphologies, limited genetic divergence (both nuclear and mitochondrial DNA), and the degree of uncertainty regarding their phylogenetic relationship, 32 allozyme loci were used to determine the levels of genetic diversity for the Grey Smoothhound, Mustelus californicus, and the Brown Smoothhound, M. henlei, and to detect species-specific nuclear markers capable of determining the existence of hybridization within northeastern Pacific Mustelus. Tissue extracts from 26 adult M. henlei collected from Santa Catalina Island, California and 17 M. californicus collected from Marina Del Rey, California were subjected to starch gel electrophoresis. Gene products of the 32 loci were resolved for all specimens of both species. All 32 loci were monoallelic in M. californicus, whereas four polyallelic loci, three diallelic and one triallelic, were resolved in M. henlei. Nine of the 32 loci exhibited complete allelic divergence between the two species (i.e., no shared alleles) and can serve as diagnostic markers to reveal potential F1 and F2 hybrids.

Mercury concentrations and trophic relations in sharks of the Pacific Ocean of Colombia

Sharks are fished for human consumption in Colombia, and fins are exported illegally to international markets. The goal was to identify differences in total mercury (THg) concentrations in fins and muscles of shark species seized in the Buenaventura port (Colombian Pacific), and to assess potential human health risks related to shark consumption. Seven species were considered in this study: Pelagic Thresher (Alopias pelagicus), Pacific Smalltail Shark (Carcharhinus cerdale), Brown Smoothhound (Mustelus henlei), Sicklefin Smoothhound (Mustelus lunulatus), Scalloped Bonnethead (Sphyrna corona), Scalloped Hammerhead (Sphyrna lewini), and Bonnethead Shark (Sphyrna tiburo), and THg was analyzed in shark tissues. 24% muscle samples concentrations were above international recommended limits for human consumption, especially for A. pelagicus and S. lewini. Stable isotopes (δ13C and δ15N) analysis showed a foraging overlapping in coastal habitats, where overfishing usually occurs. This study provides useful scientific information to develop management plans for sharks in Colombia and neighboring countries.

Mercury and selenium concentrations in different tissues of brown smooth-hound shark (Mustelus henlei) from the western coast of Baja California Sur, Mexico

A study on mercury (Hg) and selenium (Se) concentrations in the liver and muscle of brown smooth-hound shark Mustelus henlei and its principal prey items, was conducted in the western coast of Baja California Sur, Mexico. Average Hg concentrations were found to be high in the muscle than in the liver; however, Hg concentrations were below the maximum permissible limits, and hence, the consumption of this species does not constitute a risk to human health. The mean Se concentrations were higher in the liver than in the muscle. The results of Hg: Se molar ratio revealed that Se counteracts the toxicity of Hg in hepatic tissues, whereas the contrary occurs in the muscle. Significant differences in Hg and Se accumulation were observed between females and males. Biomagnification factor values >1 demonstrate a biomagnification process from its principal prey species (i.e., red crab, Pleuroncodes planipes and Pacific mackerel, Scomber japonicus).

Stable isotopic inferences on trophic ecology and habitat use of brown smooth-hound Mustelus henlei in the west coast of Baja California Sur, Mexico

The brown smoothhound shark Mustelus henlei is the most important shark species in the artisanal fisheries of the western coast of Baja California Sur, Mexico. Its trophic ecology was analyzed using carbon (13C) and nitrogen (15N) stable isotope analysis in the muscle tissue. The values of δ13C (−18.2 ± 0.6 ‰) and δ15N (17.7 ± 0.9 ‰) suggest that this species feeds in the Gulf of Ulloa throughout the year. The low values of δ13C indicate that the sharks feed in oceanic zones; while the δ15N values suggest that these sharks feed on prey that occupy a high trophic level and/or from a trophic chain with an enriched basal signal. The δ13C and δ15N values of this species do not present significant statistical differences between sexes and size. This study provides new insights regarding the habitat use of M. henlei, characterizing its preference for oceanic zones.

Mercury (Hg) and selenium (Se) content in the shark Mustelus henlei (Triakidae) in the northern Mexican Pacific.

Mercury and selenium were assessed in Mustelus henlei, which is a carnivorous predatory shark that is important for the coastal communities of the northern Mexican Pacific (NMP). Sixty-two individuals were sampled; muscle and liver were isolated and analyzed by atomic absorption spectrophotometry. The mean Hg concentrations (wet weight) obtained for muscle (0.08 ± 0.10μgg-1) and liver (0.09 ± 0.26μgg-1) were below the allowed limits (< 1.0μgg-1 Hg). The average Se concentration was 0.03 ± 0.01μgg-1 in muscle and 0.13 ± 0.05μgg-1 in liver. The Se/Hg molar ratio of muscle was 1.83; however, the selenium health benefit value (HBVSe) was of 0.08. We calculated that an adult man (70kg), an adult woman (60kg), and a child (16kg) could consume 1595, 838, and 223g/week of M. henlei muscle, respectively, without risks to health. In conclusion, the concentrations and molar ratio of Hg and Se in M. henlei muscle mean that consumption of this shark's meat does not represent neither a benefit nor a public health risk.

Bioaccumulation and trophic transfer of Cd in commercially sought brown smoothhound Mustelus henlei in the western coast of Baja California Sur, Mexico

A study on cadmium concentration in Mustelus henlei (liver and muscle) was carried out in an area influenced by natural phosphorite deposits and coastal upwelling. Our results indicate that liver (0.96 μg/g) concentrations were higher compared to the muscle (0.040 μg/g) suggesting it is on the safer level for human consumption. The male/female ratio indicates higher values (based on liver & muscle) in males (0.899 μg/g), which contributes to these differences in concentration. Higher values in the liver (0.96 μg/g) is due to the influence of phosphorite deposits in the region as well as the high metabolic activity. The other important factor responsible for these high Cd values are the prey, which also poses high values and is well supported by the biomagnification (1.08 & 4.57) of this element. The study also benefited in evaluating the environmental conditions for this particular species and elemental concentration in relation to human health.

Primary and secondary nursery areas for leopard and brown smoothhound sharks in San Francisco Bay, California

Primary and secondary nursery areas for leopard and brown smoothhound sharks in San Francisco Bay, California

Reproductive biology of the brown smooth-hound shark, Mustelus henlei (Chondrichthyes: Triakidae), off northwestern Mexico based on macroscopic and histological analyses

The brown smooth-hound shark Mustelus henlei is one of the most abundant species caught by the artisanal elasmobranch fishery off northwestern Mexico. The present study estimates the reproductive parameters for M. henlei using, for the first time, histological analysis and survey data collected from May 2008 to May 2016. Mustelus henlei was reported in the landings from February to November each year (n = 1,469). Total length (TL) varied between 450 and 1,530 mm (average = 753 mm, SD = 111). The sex ratio (male:female) was similar to the 1:1 ratio. Gravid females were caught during April, August, and November. Average fecundity was 9. Length at maturity was 656 mm TL for females and 636 mm TL for males, and length at maternity, estimated for the first time for this species, was 676 mm TL. The first phases of spermatogenesis and oogenesis were identified through histological analysis of gonads from immature individuals. Semen storage was detected in the oviducal gland of females at the terminal zone, whereas in males spermatozeugmata was detected in the seminal vesicles. According to the species reproductive parameters, M. henlei can be categorized as a species of high biological productivity among elasmobranchs and can thus support certain level of fishing pressure off northwestern Mexico if adequate fishing management and regulatory measures are employed. Some of the reproductive parameters that were estimated for this species in the present study were different from those estimated for other stocks from Mexican and United States waters.&#x0D; Key words: reproduction, length at maturity, length at maternity, semen storage, Mustelus henlei.

Temperature effects on the blood oxygen affinity in sharks.

In fish, regional endothermy (i.e., the capacity to significantly elevate tissue temperatures above ambient via vascular heat exchangers) in the red swimming muscles (RM) has evolved only in a few marine groups (e.g., sharks: Lamnidae, Alopiidae, and teleosts Scombridae). Within these taxa, several species have also been shown to share similar physiological adaptations to enhance oxygen delivery to the working tissues. Although the hemoglobin (Hb) of most fish has a decreased affinity for oxygen with an increase in temperature, some regionally endothermic teleosts (e.g., tunas) have evolved Hbs that have a very low or even an increased affinity for oxygen with an increase in temperature. For sharks, however, blood oxygen affinities remain largely unknown. We examined the effects of temperature on the blood oxygen affinity in two pelagic species (the regionally endothermic shortfin mako shark and the ectothermic blue shark) at 15, 20, and 25°C, and two coastal ectothermic species (the leopard shark and brown smooth-hound shark) at 10, 15, and 20°C. Relative to the effects of temperature on the blood oxygen affinity of ectothermic sharks (e.g., blue shark), shortfin mako shark blood was less affected by an increase in temperature, a scenario similar to that documented in some of the tunas. In the shortfin mako shark, this may act to prevent premature oxygen dissociation from Hb as the blood is warmed during its passage through vascular heat exchangers. Even though the shortfin mako shark and blue shark occupy a similar niche, the effects of temperature on blood oxygen affinity in the latter more closely resembled that of the blood in the two coastal shark species examined in this study. The only exception was a small, reverse temperature effect (an increase in blood oxygen affinity with temperature) observed during the warming of the leopard shark blood under simulated arterial conditions, a finding that is likely related to the estuarine ecology of this species. Taken together, we found species-specific differences in how temperature affects blood oxygen affinity in sharks, with some similarities between the regionally endothermic sharks and several regionally endothermic teleost fishes.

Food resource partitioning of the Mustelus lunulatus and Mustelus henlei (Elasmobranchii: Carcharhiniformes)

The feeding habits and trophic ecology of Mustelus lunulatus and Mustelus henlei in the central coast of the Colombian Pacific were evaluated and compared to determine whether there was trophic niche overlap or resource partitioning between these two sympatric shark species. A total of 59 prey items were identified and grouped into 10 taxonomic categories. Mustelus lunulatus fed in large proportion on Stomatopoda and Brachyura, whereas M. henlei fed almost exclusively on Teleostei. Dendrobranchiata, Cephalopoda, Anomura and Polychaeta complemented the diets of both species. There were significant differences in diet between the two species, and there was an ontogenetic diet shift in Mustelus lunulatus, with Stomatopoda being the main prey item of juveniles and Brachyura the main prey item of adults. Dietary overlap (by sex and size) was low between species, but it was high for each species, with significant overlap between juveniles and adults of M. lunulatus and M. henlei, and between males and females of M. henlei. There were differences in the trophic levels of the species, sexes and sizes. This study suggests there is food resource partitioning, and differing ecological function of the two Mustelus species in the food web of the study area.

Mercury levels in muscle tissue of four common elasmobranch species from the Pacific coast of Costa Rica, Central America

Mercury (Hg) is a non-essential and toxic element that is ubiquitous in the marine environment and biomagnifies through food webs. Given the high trophic position of many elasmobranch species, it is important to quantify potentially harmful trace elements like Hg in their tissues, as this is an indicator of the level of contamination in the ecosystem. This study provides the first examination of total mercury (THg) concentrations in muscle tissue of four common demersal elasmobranchs (Mustelus henlei, Raja velezi, Torpedo peruana and Zapteryx xyster) from the Pacific coast of Costa Rica. All four species showed a positive relationship between THg concentration and body size, but THg concentration did not vary with trophic position. Torpedo peruana showed the highest THg concentration (mean ± SD: 0.52 ± 0.25 mg/kg wet weight) but Z. xyster had the highest slope for the THg-size relationship. The THg concentrations found in this study were lower than those reported for similar elasmobranch species in other regions, and only one sample exceeded the concentration limit suggested for human consumption. Our results suggest that THg contamination off the Pacific coast of Costa Rica, and possibly Central America is minimal.

Metapopulation structure informs conservation management in a heavily exploited coastal shark (Mustelus henlei)

The identification of historical, environmental and biological factors influencing metapopulation connectivity is important for informing management policies and for designing conservation areas to protect biodiversity. The brown smooth-hound shark Mustelus henlei is a key component of the Mexican commercial shark fisheries, one of the largest in the world. However, Mexico lacks conservation management policies for this heavily exploited species. We conducted phylogeographic and population genetic analyses using data from mitochondrial and nuclear DNA markers and from oceanographic variables to assess metapopulation connectivity in M. henlei from the Gulf of California and the Pacific coast of Baja California. We report on historical range expansion during the Pleistocene, probably associated with the last stages of formation of the Gulf of California. From a contemporary perspective, there is significant population structure explained by spatial distance (but not by environmental factors), which contrasts with expectations of high dispersal capacity for this shark. Populationand individual-based genetic analyses suggest that both female philopatry and male-biased dispersal impact on metapopulation structure. These results highlight the importance of protecting nursery areas and habitat connectivity for the conservation management of the species. Our study clarifies important biological aspects of the brown smooth-hound shark that have implications for the design of shark management policies and marine protected areas in the Gulf of California, an iconic marine ecosystem of global significance.

Feeding ecology of common demersal elasmobranch species in the Pacific coast of Costa Rica inferred from stable isotope and stomach content analyses

Knowledge of the feeding ecology and trophic interactions of marine species is essential to understanding food web dynamics and developing ecosystem-based management approaches. Given that many top predatory fishes have experienced large population declines from coastal ecosystems, it is critical to understand the role of smaller, mesopredators in coastal food webs. This study used stomach content (SCA) and stable isotope analyses (SIA) of muscle tissue (δ13C, δ15N) to examine the feeding ecology of four common demersal elasmobranchs (Mustelus henlei, Raja velezi, Zapteryx xyster and Torpedo peruana) from the Pacific coast of Costa Rica, Central America. Specifically, we investigated: (i) size- and sex-related changes in diet; (ii) dietary changes between seasons; (iii) dietary changes across depth and latitudinal gradients; and (iv) the degree of diet overlap among species. SCA showed that M. henlei, R. velezi and Z. xyster were feeding on a wide range of teleost and decapod species, whereas teleosts dominated the diet of T. peruana. Torpedo peruana had a lower prey diversity and dietary breath than the other species. Interestingly, SIA revealed a significantly larger isotopic niche breath in Z. xyster, indicating that SIA can provide a broader perspective of diet than SCA. Both SCA and SIA showed relatively low dietary overlap among species, except between R. velezi and Z. xyster which have a similar size, mouth morphology and potentially feeding behaviour. Latitude and size were identified as important drivers of the feeding ecology of elasmobranchs; however, their effect varied considerably among species and was often influenced by other factors such as sex and depth. Season had little influence on elasmobranch diet, but our data suggested that isotopic baseline values differ between geographic regions due to differences in local biogeochemical processes and/or prey availability, and possibly in response to seasonal nutrient fluctuations. This may also indicate that some of these elasmobranchs tend to use more localized habitats along the coast. The present study increased our understanding of the feeding ecology of common demersal elasmobranch species. Moreover, trophic information of elasmobranchs provided an important baseline record to understanding how trawling fisheries may impact demersal ecosystems in Costa Rica and the Central American region.

Comparative study of enzymatic antioxidants in muscle of elasmobranch and teleost fishes

Exercise may cause an imbalance between pro-oxidants and antioxidants. In skeletal muscle, oxygen flow can increase considerably during vigorous exercise. The antioxidant system in athletes contributes to neutralize the concomitant rise in reactive oxygen species (ROS) production. The objective of this study was to compare the antioxidant system in muscle of three species of elasmobranchs and teleosts, considering differences in swimming capacity among species within each group and evolutionary differences between the two groups. Muscle samples were collected from elasmobranchs (Isurus oxyrinchus, Prionace glauca, Mustelus henlei) and teleosts (Totoaba macdonaldi, Kajikia audax and Coryphaena hippurus) in the coast of the Baja California peninsula, Mexico. The enzymatic activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST) was determined by spectrophotometry. The activity of the antioxidant enzymes CAT, GPx and GST was higher in elasmobranchs, as a group, than in teleosts. In fish species with high swimming capacities, P. glauca, K. audax and C. hippurus, antioxidant enzyme activity was higher in comparison with species with lower swimming capacities, M. henlei and T. macdonaldi. It is possible that antioxidant enzymes, particularly SOD, GPx and GST, contribute to avoidance of oxidative damage in teleost and elasmobranch species with higher swimming capacities. The antioxidant enzyme activities in fish appear to depend mainly on their swimming capacity and life style rather than the evolutionary group (elasmobranchs, teleosts).