Studies on Salt Fish: II. The Effect of Salt Concentration on Preservation

The preserving action of salt, as determined chemically and bacteriologically, increases with increasing salt concentration (8 to 32%) and decreasing temperature (21 to 10 °C). It shows in a lengthening of the period of lag before rapid increase in volatile bases. The increase begins when the bacterial count reaches 10–20 million per ml. on 10 per cent salt agar, and its rate is not influenced by salt concentration. The hypothesis is advanced that the trimethylamine oxide present in the fish is reduced very rapidly to trimethylamine when the reduction potential reaches a definite point.

The Pigments of Salmon

The red colour of the muscle flesh of the sockeye salmon (Oncorhynchus nerka) is due to the presence of two carotenoid pigments both of which have properties similar to those of astacin. Two red pigments were also found in the red muscle flesh of the steelhead salmon (Salmo gairdneri).

The Food and the Food Supply of Sockeye Salmon (Oncorhynchus nerka Walbaum) in Cultus lake, British Columbia.

The analysis of several hundred stomachs of sockeye salmon taken from Cultus lake at all seasons shows that pelagic plankton crustaceans are practically the only food of the fingerlings, and are the most important food of the older fish. The total food consumed by fingerlings, per unit bulk, is greatest in July and August, least in winter. The entomostracan food available in the lake, as determined from plankton samples, varies seasonally in a similar manner. The percentage utilization of each of the four species of Entomostraca by a fingerling sockeye population is related directly to the plankter's abundance, and inversely to its size. Individual sockeye, however, occasionally exhibit preference for smaller or less abundant species. The summer feeding of fingerlings appears to be chiefly confined to the region between 5 and 15 metres depth, which includes the thermocline and adjacent narrow strips of the epilimnion and hypolimnion. Foraging is limited upward by scarcity of food, and downward by poor illumination or low temperature. Other fish in the lake are known to compete with sockeye for plankton, but such interspecific competition is believed to be quantitatively of minor importance, in summer at least. Intraspecific competition for food in years of large sockeye populations is sufficient to reduce their rate of growth, and is probably responsible for an unusually early decline, in those years, of the summer's supply of Entomostraca.

Some Characteristics of the Enzymes of the Pyloric Caeca of Cod and Haddock

Investigation of fish enzymes for leather bates reveals that those of the pyloric caeca show their greatest influence on casein and collagen at hydrogen ion concentrations of approximately pH 8. The protease showed its maximum activity towards casein at a temperature of 45 °C. Ammonium salts at certain concentrations increased the rate of hydrolysis of collagen by about 40 per cent, but had no like stimulating effect on the hydrolysis of casein. A comparison showed that pyloric caeca enzymes were just as satisfactory as commercial leather bates or hog pancreas. When the pyloric caeca are allowed to autolyse at room temperature, the protease activity is constant for the first 24 hours, declines rapidly during the next 80 hours, and slowly thereafter. The most suitable method for preparing a dried preparation was by evaporation under partial vacuum, which, however, is accompanied by some loss of activity.

The Relation of Temperature to the Seaward Migration of Young Sockeye Salmon (Oncorhynchus nerka)

The period of seaward migration of young sockeye from Cultus lake each spring is inversely correlated with temperature conditions prevailing during the months immediately preceding. Correlating temperature readings of the outflow stream with date when twenty per cent migration occurred, a statistically significant correlation of −0.85 was obtained for February and March and −0.77 for January to March. Using air temperatures, coefficients of −0.91 for January to March and −0.74 for February and March were found. Commencement of migration coincides with vernal rise in lake temperatures. Under normal conditions, with low winter minimum, there appears to be a threshold migration temperature approximating 4.4 °C. (40°F.) but in seasons when lake temperatures are not depressed to this level a slight rise stimulates migration. Progress of migration is largely influenced by prevailing weather conditions and their effect upon temperature trends. Cessation of migration appears to be related to the setting-up of a "temperature blanket" which inhibits migration from the lake of sockeye still resident therein. These latter, showing small growth during their first year, remain in the lake until the following spring and then are among the first to migrate.

Variation in the Time of Run, Sex Proportions, Size and Egg Content of Adult Pink Salmon (Oncorhynchus gorbuscha) at McClinton Creek, Masset Inlet, B.C.

The spawning runs of pink salmon to McClinton creek, Masset inlet, B.C., in 1930, 1932, 1934, and 1936, differed little in time of appearance of the first migrant and disappearance of the last. The period occupied for the main portion of each run to reach the spawning beds depended chiefly upon rainfall and freshet conditions. Males occurred in greater numbers at the beginning of every run but a subsequent increased influx of females eventually brought about equality of the sexes in two seasons. In the third the males predominated slightly, and in the fourth the females. The average length and weight of males are consistently greater than those for females in the same year. Usually a significant increase in length occurred in both sexes from the commencement to the end of the run. In some cases a similar gain in weight was demonstrated but in others it was apparently masked by loss in weight consequent upon fasting during the spawning migration. The number of eggs per female in a given year increases with increase in length and weight.

Sexual Dimorphism in Vertebral Number in the Capelin Mallotus villosus (Muller)

Vertebral counts of capelin spawning in autumn on Vancouver Island were: males 65.65, females 65.13. Differing significantly, these demonstrate sexual dimorphism of a type rare among fishes. The sexual difference is not primarily associated with length, although there is some relationship between length and vertebral number among females. The high degree of sexual specialization in the fins is limited to size and integument and does not include meristic features.

Egg-laying and Hatching Postures and Habits of the American Lobster (Homarus americanus)

During egg-laying Homarus americanus rests ventral side upwards on the tips of its chelae and on the first two abdominal segments. The abdomen is curved, forming a pocket with a single opening between the telson and the bases of the fifth pereiopods. While hatching its eggs the animal supports itself on the tips of the walking legs and extends the abdomen upward at an angle of 20° to 45°. The swimmerets are waved violently.

Local Feeding of Kingfishers and Mergansers

On the Margaree and Apple rivers, N.S., the belted kingfisher feeds upon those fishes most available within its feeding range. In the estuaries many species are taken, but ascending a river the number becomes less until only salmon and trout (Salvelinus), or trout alone, constitute the food. By rearing a young bird it was determined that the American merganser pursues its prey by sight under water, being able to see a distance of from 10 feet (3 m.) to 2 feet (0.6 m.) or less, depending upon the clearness of the water. The bird consumes daily on the average more than a third of its weight. In nature the broods are reared up stream where young salmon are the dominant fish and constitute the major food item, with trout next. When the supply becomes scarce they shift down stream and in the estuary take the various fishes occurring there. In contrast the young red-breasted mergansers were found feeding over areas not frequented by young salmon, and the adults were confined largely to the estuary. They fed on the species available, which sometimes consisted largely of young salmon.

Physical and Chemical Characteristics of Cultus Lake, British Columbia.

Cultus lake is a rather small, fairly deep, clear lake of the western Cascade mountains, and is the home of one of the populations of Fraser river sockeye. The equable climate of the region is reflected in the low annual heat budget of the lake and its normal lack of an ice cover in winter, with continued complete or partial circulation of its water throughout that season. Judged by the low degree of hypolimnial oxygen consumption in summer, the lake is to be classed as distinctly oligotrophic. The oxygen content at all depths and seasons is sufficient for the respiration of salmonoid fishes. The water is moderately hard and slightly alkaline. Quantities of dissolved nitrates and phosphates in the water appear to be of the order characteristic of oligotrophic lakes. Silicates are present much in excess of the requirements of the lake's diatom populations. The number of adult sockeye returning to the lake in normal years is insufficient to add to its supply of nutritive salts in significant amount. Temperature observations and oxygen determinations, taken at frequent intervals for several years, have contributed to the knowledge of certain questions of general limnological interest. Such include (1) the manner in which the hypolimnion of a lake is warmed in summer; (2) the classification of the seasonal circulation periods in temperate lakes; and (3) the oxygen content of a lake at the close of vernal circulation, and its use as a standard from which to measure oxygen consumption throughout the summer.