GALIMA, M.*; KELLEY, K.M.: Relationship Between the Physiological Stress Response, Serum IGFBPs, and Growth in the Jack Mackerel,

Metabolic and somatic growth parameters were assessed in Trachurus symmetricus subjected to confinement and handling stressors. Mackerel were caught offshore near Catalina Island and placed into 50-L circular aquaria for 5 d without further disturbance (“confinement” group) followed by blood serum collection, or they were subjected to an additional 30 or 60 min of handling stress prior to blood sampling (“handling” groups). Controls were caught and immediately sampled (within 2 min). Confinement alone increased serum concentrations of glucose (>2-fold, p<0.01) and resulted in 6-fold elevations in cortisol (p<0.001), as compared with corresponding levels in control fish. With the additional handling, cortisol concentrations were elevated yet further as compared with that in the confinement group (p<0.05 at 60 min), while glucose levels did not show this trend. Serum profiles of the insulin-like growth factor-binding proteins (IGFBPs) exhibited changes reflective of a growth-inhibited state in the stressed mackerel, with the greatest magnitude of such changes evident in the individuals with the highest cortisol levels. Results thus far suggest that stress-associated cortisol may play an inhibitory role in growth via changes in the IGF system. [Support by NSF grant IBN-9600783 & NIH grant #GM50089].