A simple growth model for salmonids in hatcheries was developed from several formulations presented in the literature. The model selected was Wt0.33 = W00.33 + (T/1000)t where Wt = weight at time t (g), W0 = initial weight, T = average temperature (°C), and t = time in days. The model was chosen from a number of possible formulations on the basis of its simplicity. Additional attributes are W0.33 is linear with time, the slope of the line W0.33 vs. time (termed growth slope) is linear with temperature (i.e. T/1000) over the temperature range commonly found in hatcheries that rear salmonids, and W0.33 is easily converted to length. Tests of the model on wild stock steelhead in British Columbia hatcheries provided good results under normal operating conditions of feeding, loading, etc. Applications of the model are also presented, including the development of a growth coefficient allowing comparisons of growth rate corrected for fish size and temperature effects.Key words: growth model, salmonids, fish culture
Detailed accounts of the spawning behavior of chum salmon (Oncorhynchus keta) and rainbow trout (Salmo gairdneri) in laboratory flumes are provided. The behavioral activities, quivering, probing, and crossing over increase in frequency as a function of time prior to spawning whereas digging remains constant or decreases slightly. Maps of digging locations and movie films suggest nest shape and current pattern are monitored by the female, allowing her to intensify her digging activity near the center of the nest. Probing appears to be a signal to the male indicating approach of oviposition and also provides information to the female regarding the shape and suitability of the nest site. The probing act is also used in the synchronization of the male and female spawning acts. Changes in velocity do not appear to markedly affect nest construction either in terms of number of digs to oviposition or in size of nest constructed. It is inferred that velocity and gravel size are important insofar as they influence the construction of a suitable nest depression. Nest sites would appear to be selected on the basis of acceleration of flow rather than velocity per se though high limits must obviously exist.
Steelhead smolts Oncorhynchus mykiss reared at the Chilliwack River Hatchery in southwestern British Columbia were tagged, transported, and released at four (1982) or six (1983, 1984) locations along the Chilliwack River. Returning adults were recovered from the sport fishery within three 10-km reaches (lower, middle, and upper) situated downstream of the upper-river hatchery. Percent recoveries were highly correlated with mean smolt size at stocking (range, 61-115 g), and most returning adults were caught within the lower river. There were small but significant effects of release location on the distribution of adult steelhead recoveries in two of three reaches. Within the lower-river catch of adults, the percentage of all lower-release recoveries was 10.3 percentage points higher than the percentage of all middle-release recoveries and 10.7 points higher than the percentage of all upper-release recoveries. In the upper-river catch, the percentage of all upper-release recoveries was 5.5 and 11.4 points higher than the percentage of all middle-and lower-release recoveries, respectively. Middle-river recoveries were not disproportionately higher for any release-reach group. Similarly, among adults that returned to the hatchery channels in the upper river, on average, 43% were from the upper, 30% from the middle, and 27% from the lower reaches of release; thus, homing was strongly influenced by the rearing location. In a steelhead fishery associated with an upper-river hatchery and dependent on wild and hatchery-reared fish, transport and release of smolts affected homing of adults, but there was substantial dispersal of lower-river fish to the upper river. These findings have implications for selective management of augmented steelhead stocks.
For a variety of stock recruit systems, in which environmental variability is simulated by random normal deviates used as multipliers or divisors, Ricker (J. Fish. Res. Bd. Canada 15: 991–1006, 1958) and Larkin and Ricker (J. Fish. Res. Bd. Canada 21: 1–7, 1964) demonstrated the benefits of complete stabilization of escapement as opposed to removal of a fixed proportion of the stock each year. The present paper is primarily concerned with the response of these same systems to a pattern of stochastic modification that is more regular in form, a pattern such as might be imagined to result from long-term trends in environmental conditions. The simulations indicate that the gains derived from complete stabilization of escapement are determined solely by the variance of the modifiers — thus the pattern of modification, i.e., long- or short-term, is relevant only in terms of its influence on the variance. In addition, a check for maximum equilibrium catch using catch statistics is described.
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