Mustelus Research Articles

First fossil record of Mustelus aff. punctulatus Risso, 1826: new evidence for a smooth-hound shark population in the Late Miocene North Sea Basin

Mustelus is a problematic genus in palaeoichthyology. Due to the scarcity of fossil teeth, relative homogeneity in tooth morphology and the lack of published extant dentitions, the early history of smooth-hound sharks remains poorly understood. Recently, two teeth were collected in the Tortonian Deurne Member (Diest Formation) near Antwerp (Belgium). Surprisingly, a detailed SEM-based comparison with the extant North-Eastern Atlantic species (Mustelus mustelus, Mustelus asterias, Mustelus punctulatus) allowed assigning the fossil teeth to Mustelus aff. punctulatus. Today, this species is largely restricted to the Mediterranean and lies at the very base of the placental Mustelus clade evolution. Until now, this species remained unrecognized in the existing fossil record. By (re)evaluating isolated teeth from other upper Miocene localities in the southern North Sea Basin, the existence of a widely distributed population of Mustelus aff. punctulatus for the late Serravallian and the Tortonian can now be postulated. Thereafter, the species disappeared from the North Sea. Until today, no single record of Mustelus punctulatus is known from the Mediterranean predating the Messinian Salinity Crisis. Therefore, it is hypothesized that the current populations have their origin in southward migration from northern, Atlantic populations, and this probably after the “Zanclean Flooding”.

Observations on food and feeding habits of the common smooth hound shark, Mustelus mustelus in the Mediterranean Sea at Alexandria coast, Egypt

Observations on food and feeding habits of the common smooth hound shark, Mustelus mustelus in the Mediterranean Sea at Alexandria coast, Egypt

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.

Feeding habits of Chondrichthian Mustelus Mustelus - Smoothhound : Triakidae- in Syrian marine water

This study was performed on the smoothhound shark: Mustelus mustelus (Linnaeus, 1758), during the period between December 2005 and April 2009, in the Eastern Levant along the Syrian coast. A total of 222 specimens examined (143 females, 79 males) discerned: The monthly sampling showed: the Smoothhound shark, M. mustelus were normally caught throughout the year, mainly in spring and summer, at fishing sites from Raas Albassit to Tartus city (34º. 40΄and 35º.80΄ N, 35º.70΄and 36º.05΄ E) of the Syrian coast, from shallow water to depth 250 m. The coefficient of void of total specimens stomachs was high (C.V=61.7 %), values were almost equal between males and females, the higher value recorded for adult females (C.V =62.5 %). The prey items belong to three collections: (Bony fish, Crustaceans, and Mollusks), bony fish occupy the first position for: Coefficient of feeding (Q=1560.4), Frequency of prey index (91.8 %), Gravimetric percentage of prey index (C.P=38.6 %). Crustaceans came in the first position for Numerical Percentage of Prey Index (C.N=45.6 %).

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.

DNA barcoding reveals overlooked shark and bony fish species in landing reports of small-scale fisheries from northern Peru

Species-level identification of commercially landed fish provides pivotal information for stock assessment and fishery management. However, there is a common lack of species determination in landing records from small-scale fisheries (SSFs) worldwide. Using DNA barcoding analyses, we detected four overlooked bony fish (yellow snapper, union snook, blackspot wrasse, and steeplined drum) and one shark species (the sicklefin smooth-hound) in official landing records of SSFs from northern Peru. Of particular concern is the sicklefin smooth-hound shark Mustelus lunulatus that was found to be overlooked and could mistakenly be landed as the humpback smooth-hound M. whitneyi. Increased efforts should be made to improve species identification capacities in Peruvian fishing landings. There is an urgent need to quantify the catch levels of members of the genus Mustelus to species level. This would contribute to a better understanding of the levels of exploitation in each particular species and to improved management decisions.

Site fidelity and shallow genetic structure in the common smooth-hound shark Mustelus mustelus confirmed by tag-recapture and genetic data.

The common smooth-hound shark, Mustelus mustelus, is a widely distributed demersal shark under heavy exploitation from various fisheries throughout its distribution range. To assist in the development of appropriate management strategies, the authors evaluate stock structure, site fidelity and movement patterns along the species' distribution in southern Africa based on a combination of molecular and long-term tag-recapture data. Eight species-specific microsatellite markers (N=73) and two mitochondrial genes, nicotinamide adenine dehydrogenase subunit 4 and control region (N=45), did not reveal any significant genetic structure among neighbouring sites. Nonetheless, tagging data demonstrate a remarkable degree of site fidelity with 76% of sharks recaptured within 50 km of the original tagging location. On a larger geographic scale, dispersal is governed by oceanographic features as demonstrated by the lack of movements across the Benguela-Agulhas transition zone separating the South-East Atlantic Ocean (SEAO) and South-West Indian Ocean (SWIO) populations. Microsatellite data supported very shallow ocean-based structure (SEAO and SWIO) and historical southward gene flow following the Agulhas Current, corroborating the influence of this dynamic oceanographic system on gene flow. Moreover, no movements between Namibia and South Africa were observed, indicating that the Lüderitz upwelling formation off the Namibian coast acts as another barrier to dispersal and gene flow. Overall, these results show that dispersal and stock structure of M. mustelus are governed by a combination of behavioural traits and oceanographic features such as steep temperature gradients, currents and upwelling systems.

Historical trophic ecology of some divergent shark and skate species in the Dutch coastal North Sea zone

Over the last century the fish community of the Dutch coastal North Sea zone has lost most its shark and skate species. Whether their disappearance has changed the trophic structure of these shallow waters has not been properly investigated. In this study historical dietary data of sharks and skates, being in the past (near)-residents, juvenile marine migrants and marine seasonal visitors of the Dutch coastal North Sea zone were analyzed for the period 1946–1954. Near-resident and juvenile marine migrant species were demersal while all marine seasonal visitors species were pelagic. Based on stomach content composition, the trophic position of four of the various shark and skate species could be reconstructed. The (near)-resident species, the lesser spotted dogfish, the marine juvenile migrant, the starry smooth hound, and the benthopelagic marine seasonal visitor, the thornback ray, had a benthic/demersal diet (polychaetes, molluscs and crustaceans), while the pelagic marine seasonal visitor, the tope shark, fed dominantly on cephalopods and fishes. Diet overlap occurred for fish (tope shark and lesser spotted dogfish), for hermit crabs (lesser spotted dogfish and starry smooth hound) and for shrimps (thornback ray and starry smooth hound). Trophic position ranged from 3.2 for thornback ray preying exclusively on crustaceans to 4.6 for the tope shark consuming higher trophic prey (crustaceans and fish). The analysis indicates that most of the shark and skate species were generalist predators. The calculated trophic positions of shark and skate species indicate that those species were not necessarily at the top of the marine ecosystem food web, but they might have been the top predators of their particular ecological assemblage.

Unusual record of a multiple predation of the Patagonian seahorse Hippocampus patagonicus by the Narrownose smooth-hound Mustelus schmitti in Argentine coastal waters

Seahorses (Genus Hippocampus) are rarely reported as prey items. Their low population numbers, their ability to blend with the environment and their low palatability are the features making them an unsuitable option for predators. Five individuals of the Patagonian seahorse Hippocampus patagonicus were found in the stomach of a single narrownose smooth-hound shark Mustelus schmitti from a sample of 959 stomachs analyzed. This rare record in a single stomach out of hundreds analyzed suggests that these individuals might have clustered in a group which was detected by the opportunistic M. schmitti.

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).

Revision of the genus Mustelus (Carcharhiniformes: Triakidae) in the northern Indian Ocean, with description of a new species and a discussion on the validity of M. walkeri and M. ravidus

The species of Mustelus Linck, 1790 occurring in the northern Indian Ocean are revised and a new species, Mustelus andamanensis sp. nov., is formally described. Previously considered to be conspecific with M. mosis Hemprich & Ehrenberg, 1899, the new species is currently only known from the Andaman Sea. The Red Sea and Arabian Sea populations of Mustelus mosis differ in vertebral counts and degree of coverage of buccopharyngeal denticles in the mouth, but these characters alone are not considered strong enough evidence to separate into two species. Mustelus andamanensis sp. nov. is genetically (based on NADH2 sequences) closest to M. mosis but differs in having a subdivided palatoquadrate (vs. palatoquadrate not divided). The new species is morphologically closest to M. widodoi White & Last, 2006, but differs in several morphological characters and on a molecular level. Mustelus stevensi White & Last, 2008 is confirmed from the northern Indian Ocean for the first time based on a single specimen taken off southeastern Myanmar. Mustelus walkeri White & Last, 2008 is found to be a junior synonym of M. antarcticus Gunther, 1870. The use of buccopharyngeal patterns and vertebral counts in isolation from other morphological differences and molecular data in this genus is also discussed.

The effects of agar addition and ultrasound treatment on thermomechanical and physical properties of smooth hound (Mustellus mustellus) skin gelatin film

This study investigates the effect of agar addition and ultrasound treatment on the properties of edible films made from smooth hound (Mustellus mustellus) skin gelatin. The FTIR spectra showed the classic profile of gelatin spectrum presenting three characteristic absorption peaks related to amide I (1620–1690 cm−1), amide II (1540–1580 cm−1) and amide III (1230–1280 cm−1). The agar addition or ultrasound treatment did not cause important influence on FTIR spectra. Agar addition resulted in an improvement of the film rigidity, since blended films of gelatin:agar (25:75) showed important increase of the film tensile strength (12.3 MPa) and a decrease in elongation at break (135%), as compared to the 100% gelatin-based films. All the films were colorless (∆E < 6.8 and opacity < 2.5) and agar addition resulted in a slight increase of the L* values of the blended films that become more transparent. The ultrasound treatment had no significant effect on the mechanical and color properties. The water contact angle was increased for the blended films, which imply the increase of their hydrophobicity. At 120 s the increase in water contact angle was 11.5 and 36.6% for the gelatin:agar (50:50) and (25:75) films, respectively, as compared to the 100% gelatin-based film that suggested a decrease in surface hydrophilicity of the blended films. Agar addition (gelatin:agar; 25:75) decreased the film water solubility by 34%, which suggested that agar could improve their water resistance. Overall, agar addition improved barrier properties of smooth hound gelatin films encouraging their use as a food packaging material.

Life history of

Mustelus mustelus from the Langebaan Marine Protected Area (LMPA) has been largely protected from fishing activities for the past 30 years; therefore, its biology represents those of an unfished stock. The reproductive biology, diet, growth and maturity of M. mustelus was studied in the Langebaan Lagoon region in the south-western Cape Coast of South Africa between 2007 and 2009. In total, 217 sharks (females: 381–1734 mm total length (TL); males: 467–1267 mm TL) were examined. Sharks in the Bay represented the largest specimens among six regions, globally. Female parturition, ovulating and mating occurred between November and December after a gestation period of 10–11 months. No ontogenetic shift in diet was evident, with the diet predominantly consisting of the following three species of crustaceans; Hymenosoma orbiculare, Upogebia africana and Callichirus kraussi. The von Bertalanffy growth parameters for combined sexes were L∞ = 1594 mm TL, k = 0.15 year–1, t0 = –2.01 year (n = 95). Possible age over-estimation was investigated using micro-computed tomography, which highlighted the existence of false check marks. This study indicated that the LMPA represents a pupping, nursery and feeding ground as well as a refuge area for the largest and oldest recorded smoothhound sharks globally, emphasising its importance in spatial conservation of this species.

Reproductive biology and placentotrophic embryonic development of the smalleye smooth-hound shark, Mustelus higmani, from the south-eastern Caribbean

AbstractThe reproductive biology and embryonic development of Mustelus higmani were examined between January 2015 and December 2016 in the south-eastern Caribbean. Captures comprised 813 females (23.2–72.5 cm TL), and 960 males (22.6–62.5 cm TL). The total length at 50% maturity was estimated as 47.8 and 47.5 cm for females and males, respectively. Uterine fecundity ranged from 1 to 8 embryos and ovarian fecundity between 1 and 9 vitellogenic follicles. The time of parturition and mating season of M. higmani may occur throughout the year, peaking between November and February. The presence of pre-ovulatory ovarian follicles along with advanced embryos indicates an annual reproductive cycle for female M. higmani. The main embryonic development stages were recorded in the samples, from uterine eggs (1 to 6 per female) to term embryos (23.0–26.0 cm TL). The transition between placental pre-implantation and post-implantation occurs when embryos have attained a TL of 5.0–6.0 cm. The observation of abundant uterine histotrophic secretions in late pregnant and post-partum females demonstrates that histotrophy may intensify close to birth in this species. The local population of M. higmani appears to have relatively high productivity; nonetheless, this species is heavily harvested and lacks management measures in the study area.

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.

Environmental influence on the inter-annual demographic variation of the narrownose smooth-hound shark (Mustelus schmitti, Springer 1939) in the Northern Argentine Coastal System (El Rincón, 38–42°S)

ABSTRACT Understanding the environmental influence on the demographic structure of a shark population within a specific ecosystem has direct implications for developing effective management and conservation measures. We studied the physical environment influence on the inter-annual demographic variation of the narrownose smooth-hound shark (Mustelus schmitti) in a key coastal ecosystem. The analyses were based on the size assemblage concept of co-occurring length classes that share common traits. We used bottom-trawl datasets (n = 334) collected over 8 spring periods (1994-2012). The analyses indicated that the population was structured in eight size assemblages that represented its main ontogenetic levels. Those corresponding to sub-adult females, young adult males, and juveniles contributed to most of the population similarity. The population structure presented high (>57.7%) inter-annual dissimilarities and showed three main similarity levels with significant differences associated with a higher abundance and similarity contribution of the main assemblages. All size assemblages were more abundant in shallow (<34.5 m), warmer (>14.9 °C), and fresher (<33.24) waters. Although the temperature variations better explained the spatial distribution of abundance, the inter-annual variation in the population similarity matched the spatial coverage of low salinities (<33.5). Overall, the environmental variation explained the variability in the abundance of size assemblages in consecutive years.

Age, growth, and mortality of starspotted smooth-hound, Mustelus manazo (Bleeker, 1854) in southern West Nusa Tenggara waters

Mustelus manazo (Starspotted smooth-hound shark) is one of the important catch for small scale fisheries in West Nusa Tenggara. This species belongs to the family Triakidae. According to the IUCN Red List, the conservation status of this species is data deficient, which means that there is insufficient information to conduct a proper assessment of conservation status. The objective of this study is to estimate the age, growth and mortality of M. manazo in southern West Nusa Tenggara waters. Length data were collected from January to December 2016 in Tanjung Luar Port, West Nusa Tenggara. Electronic length-frequency analysis (ELEFAN) in R Statistics with package “TropFishR” was used to estimate the population parameter. Length converted catch curve analysis was used to estimate the total mortality. The results showed that von Bertalanffy growth model for male was Lt=122 (1-e(-0.1(t+0.01))), for female was Lt=130 (1-e(-0.18(t+0.02))) and for combined sex was Lt=132 (1-e(-0.1(t+0.01))). Total mortality was estimated at 0.25 year −1. The results from this study represent basic information to support fisheries management of M. manazo in Indonesia.

Historical biogeography of smoothhound sharks (genus Mustelus) of Southern Africa reveals multiple dispersal events from the Northern Hemisphere

Members of the smoothhound shark genus Mustelus display a widespread distribution pattern across ocean basins with a high degree of sub-regional endemism. The patterns and processes that resulted in smoothhound biodiversity and present-day distribution remain largely unknown. We infer the phylogenetic relationships of the genus Mustelus, based on sequence data (3474 bp) from three mitochondrial genes (CR, NADH-2 and 12S-16SrRNA) and a nuclear gene (KBTBD2) from seven species of Mustelus distributed across the eastern Atlantic- and Indo-Pacific oceans. Using the CR and KBTBD2 dataset, we infer the phylogeographic placement of Old World Mustelus, with particular reference to species from southern Africa. Using a near-complete phylogeny of the genus including Old World and New World species of Mustelus and publicly available sequences of the NADH-2 gene, we found supporting evidence indicating a major cladogenic event separating placental and aplacental species. Biogeographical analyses further revealed that the radiation of Mustelus in the southern African region was driven primarily by long-distance dispersal during the upper Miocene to lower Pleistocene. The placement of the placental blackspotted smoothhound Mustelus punctulatus at the base of the placental non-spotted clade suggests the secondary loss of black spots in the genus, and this was also supported by the ancestral state reconstruction. The results furthermore suggest that the Southern Hemisphere species of the genus arose from multiple separate dispersal events from the Northern Hemisphere which is in line with the earliest record of Mustelus in the Northern Hemisphere.

Ontogenetic trophic segregation between two threatened smooth-hound sharks in the Central Mediterranean Sea

Elasmobranchs are among the species most threatened by overfishing and a large body of evidence reports their decline around the world. As they are large predators occupying the highest levels of marine food webs, their removal can alter the trophic web dynamic through predatory release effects and trophic cascade. Suitable management of threatened shark species requires a good understanding of their behaviour and feeding ecology. In this study we provide one of the first assessments of the trophic ecology of the “vulnerable” smooth-hounds Mustelus mustelus and M. punctulatus in the Central Mediterranean Sea, based on stomach contents and stable isotope analyses. Ontogenetic diet changes were addressed by comparing the feeding habits of three groups of individuals: juveniles, maturing and adults. Our results highlighted that the two species share a similar diet based mostly on the consumption of benthic crustaceans (e.g. hermit crabs). Their trophic level increases during ontogeny, with adults increasing their consumption of large-sized crustaceans (e.g. Calappa granulata, Palinurus elephas), cephalopods (e.g. Octopus vulgaris) and fish (e.g. Trachurus trachurus). Our results provide also evidence of ontogenetic shifts in diet for both species showing a progressive reduction of interspecific trophic overlap during growth. The results of this study contribute to improve the current knowledge on the trophic ecology of these two threatened sharks in the Strait of Sicily, thus providing a better understanding of their role in the food web.

A new animal-borne imaging system for studying the behavioral ecology of small sharks: laboratory and field evaluations

ABSTRACT The use of animal-borne imaging and environmental data collection systems (AVEDs) can provide behavioral and ecological information of animals that many other technologies cannot usually offer. However, many previous AVEDs have been designed for larger sharks, and there is a need for a technology that permits the collection of behavioral and ecological data for small sharks. In this study, we developed and tested the Shark Harness, a novel AVED technology for small to medium size sharks, in both the laboratory and the field. In the laboratory, the swimming behavior of seven dusky smoothhound sharks (Mustelus canis; n = 7) ranging in size from 90.00–114.30 cm total length (TL) was assessed. When compared to unmanipulated individuals, sharks fitted with the Shark Harness exhibited no significant variations in both swimming duration (p = 0.63) and vertical positioning (0.99), whereas a minor, yet statistically significant, increase in tail beat frequency (p = 0.016) was observed. In the field, six dusky smoothhound sharks (90–110.28 cm TL) equipped with the Shark Harness were released in waters near Montauk, New York, USA. Field data suggest that the Shark Harness can be used to assess fine-scale movements, heterospecific interactions, and immediate post-release survivorship of dusky smoothhound sharks and other small sharks (≥80 cm TL) in a wild setting. However, future modifications are required prior to redeployment in a wild setting, including a more cryptic and hydrodynamic design, in order to obtain a more accurate representation of the respective animal’s natural behavior and interactions with con- and hetero-specifics.