Impact of disease on the survival of three commercially fished species.

Recent increases in emergent infectious diseases have raised concerns about the sustainability of some marine species. The complexity and expense of studying diseases in marine systems often dictate that conservation and management decisions are made without quantitative data on population-level impacts of disease. Mark-recapture is a powerful, underutilized, tool for calculating impacts of disease on population size and structure, even in the absence of etiological information. We applied logistic regression models to mark-recapture data to obtain estimates of disease-associated mortality rates in three commercially important marine species: snow crab (Chionoecetes opilio) in Newfoundland, Canada, that experience sporadic epizootics of bitter crab disease; striped bass (Morone saxatilis) in the Chesapeake Bay, USA, that experience chronic dermal and visceral mycobacteriosis; and American lobster (Homarus americanus) in the Southern New England stock, that experience chronic epizootic shell disease. All three diseases decreased survival of diseased hosts. Survival of diseased adult male crabs was 1% (0.003-0.022, 95% CI) that of uninfected crabs indicating nearly complete mortality of infected crabs in this life stage. Survival of moderately and severely diseased striped bass (which comprised 15% and 11% of the population, respectively) was 84% (70-100%, 95% CI), and 54% (42-68%, 95% CI) that of healthy striped bass. The disease-adjusted yearly natural mortality rate for striped bass was 0.29, nearly double the previously accepted value, which did not include disease. Survival of moderately and severely diseased lobsters was 30% (15-60%, 95% CI) that of healthy lobsters and survival of mildly diseased lobsters was 45% (27-75%, 95% CI) that of healthy lobsters. High disease mortality in ovigerous females may explain the poor recruitment and rapid declines observed in this population. Stock assessments should account for disease-related mortality when resource management options are evaluated.

Cross matching of blood in carcharhiniform, lamniform, and orectolobiform sharks.

The transfusion of whole blood in elasmobranchs could provide cardiovascular support following hemorrhage. Since donor and recipient compatibility is not known, a technique was established to allow cross matching of red blood cells and serum in sharks. Cross matching was carried out among 19 individuals from seven species: the nurse shark (Ginglymostoma cirratum), sandbar shark (Carcharhinus plumbeus), sandtiger shark (Carcharias taurus), white-spotted bamboo shark (Chiloscyllium plagiosum), brown-banded bamboo shark (Chiloscyllium punctatum), zebra shark (Stegostoma fasciatum), and spotted wobbegong (Orectolobus maculatus). Negative cross-matches showed no agglutination or hemolysis, suggesting that donor and recipient would be compatible. Cross-matches between conspecifics were all negative (sandbar, sandtiger, nurse, and white-spotted bamboo sharks). All cross-matches between sandbar and sandtiger sharks were also negative. Positive crossmatches consisted of agglutination or hemolysis of red blood cells, suggesting that the donor and recipient would be incompatible. Strong positive reactions occurred, for example, with red blood cells from sandtiger and sandbar sharks and serum from nurse sharks. Cross matching should be carried out in elasmobranchs prior to any blood transfusion.

Immunoglobulins in the eggs of the nurse shark, Ginglymostoma cirratum.

Elasmobranchs, which include the sharks, skates, and rays, emerged over 450 million years ago and are the oldest vertebrates to possess an adaptive immune system. They have evolved diverse reproductive modes, with a variety of physiological adaptations that enhance reproductive success. The nurse shark, Ginglymostoma cirratum, is an aplacental, viviparous elasmobranch in which the egg and its associated vitelline vasculature are the primary route for maternal-embryonic interactions. During gestation, nurse shark embryos hatch from their eggcases and develop free in the uterus, which is flushed regularly with seawater. Similar to higher vertebrates, embryonic and neonatal nurse sharks possess an immune system that is not fully competent. In birds and bony fishes, maternal immunoglobulins (Ig) stored in the egg during oogenesis confer protective immunity to embryos during gestation. However, early research suggested that such transfer of passive immunity does not occur in sharks. To better understand how elasmobranch embryos are protected from waterborne pathogens during this potentially vulnerable time, we have re-examined the existence of Igs in elasmobranch eggs. Using monoclonal antibodies, we establish the presence of two classes of Igs in nurse shark eggs: 7S IgM and IgNAR. The potential transfer of immunoglobulins from elasmobranch eggs is discussed.

First report of Streptococcus parauberis in wild finfish from North America.

Streptococcosis is a common cause of pathology and mortality in fishes resulting in significant economic losses for the aquaculture industry. One etiologic agent of the disease, Streptococcus parauberis, has been associated with fish mortalities in Spain and Korea. Here we report the first identification of S. parauberis in wild finfish in Chesapeake Bay, USA. Gram-positive cocci were isolated from the spleens of striped bass, Morone saxatilis, and identified via species-specific primers and 16S rRNA gene sequencing. Biochemical characterization and antibiotic susceptibility tests were used to compare local isolates to isolates infecting aquacultured fishes and dairy cattle. This is also the first report of a plasmid in S. parauberis from any host.