359 research outputs found
Length at maturity in three pelagic sharks (Lamna nasus, Isurus oxyrinchus, and Prionace glauca) from New Zealand
Reproductive data collected from porbeagle, shortfin mako,
and blue sharks caught around New Zealand were used to estimate the median length at maturity. Data on clasper development, presence or absence of spermatophores or spermatozeugmata, uterus width, and pregnancy were collected by observers aboard tuna longline vessels. Direct
maturity estimates were made for smaller numbers of sharks sampled at recreational fishing competitions. Some data sets were sparse, particularly over the vital maturation
length range, but the availability of multiple indicators of maturity made it possible to develop estimates for both sexes of all three species.
Porbeagle shark males matured at 140â150 cm fork length and females at about 170â180 cm. New Zealand porbeagles therefore mature at shorter lengths than they do in the North Atlantic Ocean. Shortfin mako males matured at 180â185 cm and females at 275 â285 cm. Blue shark males matured at about 190 â195 cm and females at 170â190 cm; however these estimates were hampered by small sample sizes, difficulty obtaining representative samples from a population segregated by sex and maturity stage, and maturation that occurred over a wide length range. It is not yet clear whether regional differences in median maturity exist for shortfin mako an
Checklist of the Coastal Fishes of Lord Howe, Norfolk, and Kermadec Islands, Southwest Pacific Ocean
A checklist of coastal fishes includes 433 species from Lord Howe
Island, 254 from Norfolk Island, and 145 from the Kermadec Islands. Tropical
and subtropical species dominate all three faunas, but the proportion of tropical
species decreases, and the proportion of subtropical species increases, from west
to east. Subtropical species are the most abundant individual fishes at all three
islands. Only 4.6% of the combined fauna is endemic, with individual island
endemism even lower (1.2-2.1 %). The fish faunas of the three islands appear to
have originated mainly by larval dispersal from Australia and the Coral Sea.
Evidence for present-day dispersal is discussed. Faunal relationships among
the subtropical islands of the western, central, and eastern South Pacific are
examined. In the South Pacific as a whole, there is a high positive correlation
between coastal fish diversity and hermatypic coral diversity
Re-identification of a lamnid shark embryo
nant female lamnid shark was caught that the morphometric arguments in the Strait of Messina, Mediterra- used by Sanzo (1912) did not rule out nean Sea. She was reported to contain the shortfin mako (Isurus oxyrinchus 25â30 embryos, one of which was Rafinesque, 1810) but that the high saved and taken to the local Marine fecundity of 25â30 was more consis-Institute, where it was subsequently tent with C. carcharias than with I. examined by Sanzo (1912). The male oxyrinchus or a Lamna species. A lack embryo measured 36.1 cm total length of information on lamnid reproduction (TL), weighed 800 g, and had a greatly and the misidentification of a likely distended abdomen, as is typical of Galeorhinus galeus (Stevens2) with a embryos of oophagous lamnoid sharks litter of 30 as Lamna by Neill (1811), (Gilmore, 1993). The mother and the may have led Sanzo (1912) to consider remaining embryos were not saved. the porbeagle Lamna nasus (Bon-Because Sanzo was not able to exam- naterre, 1788) instead of the shortfin ine the adult female from which the mako as the most likely alternativ
Sympathy for the Devil: A Conservation Strategy for Devil and Manta Rays
Background International trade for luxury products, medicines, and tonics poses a threat to both terrestrial and marine wildlife. The demand for and consumption of gill plates (known as Peng Yu Sai, âFish Gill of Mobulid Rayâ) from devil and manta rays (subfamily Mobulinae, collectively referred to as mobulids) poses a significant threat to these marine fishes because of their extremely low productivity. The demand for these gill plates has driven an international trade supplied by largely unmonitored and unregulated catches from target and incidental fisheries around the world. Scientific research, conservation campaigns, and legal protections for devil rays have lagged behind those for manta rays despite similar threats across all mobulids.
Methods To investigate the difference in attention given to devil rays and manta rays, we examined trends in the scientific literature and updated species distribution maps for all mobulids. Using available information on target and incidental fisheries, and gathering information on fishing and trade regulations (at international, national, and territorial levels), we examined how threats and protective measures overlap with species distribution. We then used a species conservation planning approach to develop the Global Devil and Manta Ray Conservation Strategy, specifying a vision, goals, objectives, and actions to advance the knowledge and protection of both devil and manta rays.
Results and Discussion Our literature review revealed that there had been nearly 2.5-times more âmantaâ-titled publications, than âmobulaâ or âdevil rayâ-titled publications over the past 4.5 years (January 2012âJune 2016). The majority of these recent publications were reports on occurrence of mobulid species. These publications contributed to updated Area of Occupancy and Extent of Occurrence maps which showed expanded distributions for most mobulid species and overlap between the two genera. While several international protections have recently expanded to include all mobulids, there remains a greater number of national, state, and territory-level protections for manta rays compared to devil rays. We hypothesize that there are fewer scientific publications and regulatory protections for devil rays due primarily to perceptions of charisma that favour manta rays. We suggest that the well-established species conservation framework used here offers an objective solution to close this gap. To advance the goals of the conservation strategy we highlight opportunities for parity in protection and suggest solutions to help reduce target and bycatch fisheries
Extinction risk and conservation of the world\u27s sharks and rays
The rapid expansion of human activities threatens ocean-wide biodiversity. Numerous marine animal populations have declined, yet it remains unclear whether these trends are symptomatic of a chronic accumulation of global marine extinction risk. We present the first systematic analysis of threat for a globally distributed lineage of 1,041 chondrichthyan fishes—sharks, rays, and chimaeras. We estimate that one-quarter are threatened according to IUCN Red List criteria due to overfishing (targeted and incidental). Large-bodied, shallow-water species are at greatest risk and five out of the seven most threatened families are rays. Overall chondrichthyan extinction risk is substantially higher than for most other vertebrates, and only one-third of species are considered safe. Population depletion has occurred throughout the world’s ice-free waters, but is particularly prevalent in the Indo-Pacific Biodiversity Triangle and Mediterranean Sea. Improved management of fisheries and trade is urgently needed to avoid extinctions and promote population recovery
Genetic Diversity of the Cestode Echinococcus multilocularis in Red Foxes at a Continental Scale in Europe
Echinococcus multilocularis is a tapeworm of the red fox, which represents a considerable health threat to respectively infected humans. Main endemic areas are located in China, Siberia, and central Europe. Alarmed by an emerging or reemerging situation in Europe, the question of how the parasite gets spatially and temporally spread and transmitted becomes essential to prepare appropriate control programs. The question was tackled by using genetic data on a large sample size of E. multilocularis adult stage tapeworms, combined with geographical site location data input. The historically documented endemic area, represented by the northern Alpine arch, was shown to harbour the highest genetic richness and diversity, as compared to surrounding areas in northern and eastern Europe. The spatial and temporal spread of different E. multilocularis genotypes in Europe seems to be ruled by a founder event, linked to exportation of parasites from the central core to newly identified (western and eastern) areas or subregions, where these parasites could subsequently disseminate under geographical separation from the original foci
Reproductive aspects of the oceanic whitetip shark, Carcharhinus longimanus (Elasmobranchii: Carcharhinidae), in the equatorial and southwestern Atlantic Ocean
The present study sought to study the reproductive biology of the oceanic whitetip shark, Carcharhinus longimanus, in the equatorial and southwestern Atlantic Ocean. A total of 234 specimens were collected as bycatch during pelagic longline fisheries targeting tunas and swordfish, between December 2003 and December 2010. The fishing area was located between latitudes 10N and 35S and longitudes 3E and 40W. Of the 234 individuals sampled, 118 were females (with sizes ranging from 81 to 227 cm TL, total length) and 116 males (ranging from 80 to 242 cm TL). The reproductive stages of the females were classed as immature, mature, preovulatory and pregnant, while males were divided into immature, maturing and mature. The size at maturity for females was estimated at 170.0 cm TL, while that for males was between 170.0 and 190.0 cm TL. Ovarian fecundity ranged from 1 to 10 follicles and uterine fecundity from 1 to 10 embryos. The reproductive cycle of this species is most likely biennial, with parturition occurring once every two years.info:eu-repo/semantics/publishedVersio
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