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.
Dose-response experiments were conducted at 14 and 24°C to evaluate the efficacy and physiological effects of tricaine methanesulfonate (MS-222) to induce and maintain surgical anesthesia in juvenile Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus). Anesthetic induction time, duration of hyperactivity, recovery time and total handling time of fish were inversely related to MS-222 concentration and water temperature. Minimum effective concentration of MS-222 to maintain anesthesia with fewest signs of stress was 85 mg L )1 . Sensitivity to stimuli and body movements progressively increased when fish were exposed to a lower maintenance concentration (70 mg L )1 ) of MS-222, resulting in reduced biopsy success rates and traumatic injury to internal organs during laparoscopy as fish regained consciousness. Anesthesia with MS-222 resulted in bradychardia, near medullary collapse, elevated signs of stress (plasma cortisol and reddening of the skin) and a generalized hemo-concentration consisting of erythrocyte swelling and increased protein and monovalent ion concentrations. Magnitude of hematologic changes and stress indicators increased with decreasing MS-222 concentration and increased water temperature while plasma chemistry changes increased in magnitude with decreasing MS-222 concentration. This study demonstrates that rapid induction of surgical anesthesia with a relatively high concentration of MS-222 results in reduced signs of physiological stress, and that empirical evaluation of maintenance dosage is important to achieve the best balance between safety, efficacy and stressful side effects for invasive surgical procedures.
Sex and reproductive maturity of Atlantic and shortnose sturgeon were determined by visual examination of the gonads using laparoscopy, and were validated by histological examination of gonadal biopsies. Surgical anesthesia was induced in all fish with 250 mg L )1 tricaine methanesulfonate (MS-222) and maintained throughout procedures with 85 mg L )1 MS-222 on a mobile surgical cart. A pair of Ternamian EndoTip cannulae installed through the ventral body wall in each fish, allowed access for a 5-mm rigid laparoscope and biopsy forceps. Video endocamera use with the laparoscope, following air insufflation of the coelom, provided detailed, high quality imagery to aspirate the swim bladder, examine the gonad and collect biopsies without inducing iatrogenic trauma. Germinal tissue of all immature males, 25% of immature female shortnose sturgeon and 45% of immature female Atlantic sturgeon were concealed by fat preventing sex determination by visual assessment. Morphological features of gonads were used to determine sex in all remaining fish and were 100% in concordance with histological findings. Relative amount of gonadal fat; gonad size and color; presence of testicular lobes or ovarian lamellae; and color, size and density of oocytes were useful in determining reproductive stage. Gonad morphology of each reproductive stage was similar in Atlantic and shortnose sturgeon. All captive Atlantic sturgeon survived laparoscopy, gained weight at the same rate as unexamined fish and scars from incisions were no longer evident 9-12 months after surgery. Laparoscopic procedures presented here offer a safe and highly reliable way to determine sex and reproductive status for Atlantic and shortnose sturgeon.
Background The imperiled status of Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus), a large, long‐lived, anadromous fish found along the Atlantic coast of North America, has prompted efforts at captive propagation for research and stock enhancement. Objective The purpose of this study was to establish hematology and plasma chemistry reference intervals of captive Atlantic sturgeon maintained under different culture conditions. Methods Blood specimens were collected from a total of 119 fish at 3 hatcheries: Lamar, PA (n = 36, ages 10–14 years); Chalk Point, MD (n = 40, siblings of Lamar); and Horn Point, Cambridge, MD (n = 43, mixed population from Chesapeake Bay). Reference intervals (using robust techniques), median, mean, and standard deviations were determined for WBC, RBC, thrombocytes, PCV, HGB, MCV, MCH, MCHC, and absolute counts for lymphocytes (L), neutrophils (N), monocytes, and eosinophils. Chemistry analytes included concentrations of total proteins, albumin, glucose, urea, calcium, phosphate, sodium, potassium, chloride, and globulins, AST, CK, and LDH activities, and osmolality. Results Mean concentrations of total proteins, albumin, and glucose were at or below the analytic range. Statistical comparisons showed significant differences among hatcheries for each remaining plasma chemistry analyte and for PCV, RBC, MCHC, MCH, eosinophil and monocyte counts, and N:L ratio throughout all 3 groups. Therefore, reference intervals were calculated separately for each population. Conclusions Reference intervals for fish maintained under differing conditions should be established per population.
Preserving freshly collected blood in 10% formalin is a reliable method to maintain cell morphology for manual counts for up to 1 month post collection. This is especially useful for field studies, where laboratory access is limited. Further evaluation is needed to determine the clinical usefulness of the manual RBC count in fish.
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