Stress Response and Posttransport Survival of Hybrid Striped Bass Transported with or without Clove Oil

Abstract

A study was undertaken to determine whether stress responses and associated mortality in hybrid striped bass (white bass Morone chrysops × striped bass M. saxatilis) during and after transport could be mitigated by use of anesthesia with low concentrations of clove oil (10 μL/L of water) during transport. Stress indicators, including plasma cortisol, glucose, chloride (Cl⁻), sodium (Na⁺), potassium (K⁺), and calcium (Ca⁺⁺) concentrations, were determined for hybrid striped bass sampled (1) initially from ponds, (2) after seining (45 min), (3) immediately after a 3-h transport, and (4) at 24 h posttransport (recovery); these values were compared with those of captive control fish. Fish anesthetized with clove oil during transport exhibited prolonged elevation of cortisol concentrations (124.3 ± 13.2 ng/mL, mean ± SE) at 24 h posttransport, while fish not exposed to anesthetic during transport recovered rapidly (to 34.1 ± 13.3 ng/mL) within 24 h. Plasma glucose concentrations in hybrid striped bass exposed to clove oil during transport were significantly (α = 0.05, P < 0.05) elevated (135.1 ± 5.6 mg/dL) immediately after transport and then decreased by 24 h posttransport (84.3 ± 3.4 mg/dL) compared with the 24-h posttransport level for fish transported without anesthetic (101.0 ± 5.0 mg/dL). Plasma electrolyte (Na⁺, Cl⁻, and K⁺) concentrations indicated that osmoregulatory distress occurred after transport in hybrid striped bass transported with clove oil, while electrolyte changes were less severe in fish transported without anesthesia. No hydromineral imbalance occurred based upon plasma Ca⁺⁺ concentrations in either treatment. High mortality occurred within 7 d posttransport in both treatment groups but was not significantly different (P < 0.05) between the treatments. Observed mortality was primarily, if not entirely, due to Flavobacterium columnare infection. Hybrid striped bass transported during light clove oil sedation took longer to recover and exhibited no improved survival or disease resistance compared with fish transported without anesthesia. No potential benefit of transporting hybrid striped bass under anesthesia induced by clove oil is evident.