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.