A comparison of hematology, plasma chemistry, and injuries in Hickory shad (Alosa mediocris) captured by electrofishing or angling during a spawning run.

BACKGROUND: Declines in Hickory shad (Alosa mediocris) populations in Chesapeake Bay have prompted efforts at captive propagation of wild broodfish for stock enhancement and research. OBJECTIVE: The objectives of this study were to evaluate injuries sustained, and immediate and delayed (24 hours) effects on blood variables related to 2 fish capturing methods (electrofishing [EF] and angling). METHODS: Blood specimens were collected from fish immediately following capture by EF and angling (n = 40 per sex and capture method) from the Susquehanna River (MD, USA). Additional fish (n = 25 per sex and capture method) were collected on the same day, placed in holding tanks and bled 24 hours following capture. Blood data that were non-Gaussian in distribution were transformed (Box-Cox), and effects of sex, method of capture, and holding time were tested using ANOVA with general linear models. Fish were evaluated for injuries by necropsy and radiography. RESULTS: Sex-specific differences were observed for RBC, HGB, PCV, MCH, MCHC, total proteins (TP), globulins, glucose, calcium, AST, CK, and lactate, while RBC, HGB, PCV, MCV, MCH, MCHC, TP, albumin, globulins, glucose, potassium, sodium, AST, CK, and lactate differed significantly by fish capturing method. Electrofishing may have induced greater disruption in blood variables, but mortality (4%) was not significantly different compared to angling. CONCLUSIONS: Electrofishing for Hickory shad using a constant DC voltage resulted in numerous hematologic and biochemical changes, with no additional injuries or deaths compared to angling. Capture method must be considered when evaluating fish condition, and blood variables should be partitioned by sex during spawning season.

Preserving whole blood in formalin extends the specimen stability period for manual cell counts for fish.

BACKGROUND: Total blood cell counts for fish are challenging, especially due to cell fragility. Thrombocyte aggregation, cell distortion, and lysis can occur within hours of collection; therefore, hemocytometer counts may not be possible for large sample numbers. Preserving whole blood in formalin offers a simple way to extend the specimen stability period for cell counts. OBJECTIVES: The objectives of this study were to characterize and compare the analytical performance of the Natt-Herrick method for fish blood cell counts using freshly collected and formalin-fixed specimens. METHODS: Specimens from 11 elasmobranch species (n = 36) were compared for WBC counts. WBC, RBC, and thrombocyte counts from 50 striped bass, Morone saxatilis, were compared including 2 time points for the formalin-preserved cells (appr. 1-week and 1-month storage). Coefficient of variation (CV), bias, and total error (TEcalc ) were calculated. TEcalc was compared with allowable total error (TEa ) defined by the Clinical Laboratory Improvements Amendment (CLIA) for human blood cell counts. RESULTS: The CV and TEcalc for fresh and fixed WBC and thrombocyte counts met CLIA limits. In both the fresh and preserved cells, the RBC CV and TEcalc were nearly 3 times higher than the TEa . CONCLUSIONS: 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.

Determination of hematology and plasma chemistry reference intervals for 3 populations of captive Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus).

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.

Low prevalence of splenic mycobacteriosis in migratory striped bass Morone saxatilis from North Carolina and Chesapeake Bay, U.S.A.

Mycobacteriosis is a chronic bacterial disease causing an ongoing epizootic in striped bass Morone saxatilis in Chesapeake Bay, U.S.A. Prevalence of disease is high in pre-migratory fish, and multiple species of Mycobacterium spp. have been isolated. However, prevalence of mycobacteriosis in the coastal migratory population is unknown and is of concern to multiple coastal states, as disease-related mortality may impact the long-term health of the population. Histological examinations of spleens collected from fish caught by recreational anglers during the winter fishery in coastal North Carolina (2005-2006, n=249) and during the spring fishery in Chesapeake Bay (2006, n=120) indicated a low prevalence of mycobacteriosis (6.8% of all fish examined) in comparison to smaller, pre-migratory Chesapeake Bay fish. Genus-level PCR and subsequent sequencing of the 16-23S intergenic transcribed spacer (ITS) region revealed that all bacteria were phylogenetically related, but species is unknown. Location of survey, gender of fish, and total length of fish had no significant effect on prevalence of mycobacteriosis, parasitic granulomas, or the density of splenic granulomas (p > 0.05). These results may indicate that either granulomas resolve after Chesapeake Bay fish enter the coastal migratory population, or that there is disease-related mortality among pre-migratory Chesapeake Bay fish.