Juvenile salmon in the Nanaimo area, 1975. 2, Length, weight, and growth / by M.C. Healey, R.V. Schmidt, F.P. Jordan, and R.M. Hungar.: Fs97-4/1438E-PDF

This report documents the size and seasonal changes in size of chum and chinook fry captured in the Nanaimo area in 1975. Chum fry, migrating downstream in the Nanaimo River averaged 36 mm fork length (0.41 g). Fry captured on the Nanaimo River mud flat and on beaches some distance from the river mouth averaged only slightly larger than downstream migrants in size, however, there were more large fish among the catches away from the river mouth than in catches on the mud flat. Fry captured in 4-10 m of water or in >20 m were progressively larger on average, although catches still contained a significant number of small fish. Average size of fry captured in shallow water increased only slightly with season, but the size of fry captured away from shore increased rapidly in size after mid May, and fry captured over deep water during the first week of July (the last week of sampling) averaged 88.8 mm fork length (7.54 g). Chinook fry migrating downstream in the Nanaimo River averaged 38 mm fork length (0.57 g). Chinook fry remained on the Nanaimo River mud flat until they reached a length of about 70 mm when they apparently moved seaward, and contributed to catches in June and July. Length frequency histograms for chum captured by different gear each week were often asymmetrical or multimodal. A possible explanation for this is that sampling was inadequate and did not truly represent population structure each week. Growth rate of marked chum fry averaged greater than 5% of body weight per day for 5 different mark series. Fry migrating midway through the run grew most rapidly, but differences between marked groups were small.

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