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The effects of catch and release angling on muscle physiology, survival and gamete viability were examined in wild Atlantic salmon (Salmo salar), just prior to spawning. Lactate in the white muscle increased to 37.4 μmol∙g−1 after angling and recovered within 4 h. Muscle pH decreased from 7.46 at rest to 6.80 following angling, but returned to resting levels within 2 h. White muscle concentrations of PCr, ATP, and glycogen were depleted by 74, 46, and 73%, respectively, following angling. ATP and PCr returned to resting levels within 2 h, but glycogen did not recover until 12 h. The absence of significant changes in blood glucose indicated that the stress response was minimal in salmon angled under these conditions (6 °C). There were also no mortalities among 20 salmon that were angled and transported to the hatchery. Multi-sea-winter (MSW) salmon (> 63 cm) required a longer period to angle to exhaustion than grilse (< 63 cm), but the physiological disturbance was less in MSW salmon. The survival of eggs from angled and nonangled salmon was 98 and 97%, respectively. Together, these results support the strategy of a late-season catch and release fishery for Atlantic salmon.

Anadromous Atlantic salmon (Salmo salar) were collected during their spawning migration along the Exploits River, Newfoundland, in 1996 and analyzed for stable-isotope ratios (δ13C and δ15N) and tissue concentrations of protein and lipid. Fish became progressively more 13C enriched during the spawning migration (about -24 to -19‰), and the degree of enrichment was dependent on tissue type (red muscle: +4.1‰, liver: +2.6‰, white muscle: +1.3‰). Only liver showed consistent changes in δ15N, as overwintering kelts (13.5 ± 0.8‰) were about +2‰ more enriched than upstream migrants (11.4 ± 1.5‰). Isotopic enrichment in migrating salmon appeared to result from mobilization, reorganization, and catabolism of stored lipid and protein reserves associated with the cessation of feeding upon entering freshwater. The most significant correlations existed between lipid content and δ13C in red muscle (r2 = 0.67) and protein content and δ15N in liver (r2 = 0.32). This study shows that fasting affects the stable-isotope ratios of both carbon and nitrogen in anadromous fishes and that nutritional status should be considered when inferring food web relationships from the isotopic compositions of migrating salmonids.

Atlantic salmon Salmo salar, returning to freshwater to spawn, were angled and then terminally sampled to test the hypothesis that angling during warmer summer months (water temperatures of 20 ± 2°C) increases the magnitude of physiological disturbances in the white muscle. Angling immediately reduced white muscle ATP and phosphocreatine stores, but these high-energy phosphates were replenished within 2-4 h. Intramuscular glycogen stores were nearly depleted after angling, but unlike the response by salmon angled in the fall at 6°C, there was no glycogen resynthesis during the 4-h recovery period. Marked increases in white muscle lactate and the postexercise metabolic proton load (AH^) accompanied glycogen depletion. The time course of lactate elimination and AH^ correction, however, was much slower than previously observed in fall-angled salmon. Finally, considerable delayed postangling mortality (40%) was observed in a subgroup of Atlantic salmon that were angled at 22°C. We conclude that angling in warm summer water impairs restorative processes and increases the susceptibility of Atlantic salmon to delayed postangling mortality. We suggest that anglers can mitigate the magnitude of angling-induced physiological disturbances in Atlantic salmon during midsummer by minimizing playing time and postangling air exposure.

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