The change from a fishery for reduction to meal and oil to one primarily for roe resulted in major shifts in the herring fishing grounds on Canada's west coast. To meet management needs for the new fishing pattern, the former stock concept of seven "populations" was revised into 35 "management units." Reanalysis of tag recovery data for the period 1937–67, in terms of the 22 management units represented, showed a degree of homing between 66 and 96% for 18 of these management units. This is comparable to the homing displayed by the seven former populations (54–84%) estimated from essentially the same data base. Homing to some of the more isolated management units was comparable to that for the six major divisions of the coast (77–94%), as currently defined. Stevenson's (1954) conclusion "… the herring of British Columbia tend to form a series of integrating populations" is supported by the present analysis.Key words: Clupea harengus pallasi, tagging, homing, stocks, populations

The euryplastic Pacific herring (Clupea harengus pallasi) generally encounters temperatures ranging between 0 and 10 °C throughout its distribution during the maturation and spawning of adults, incubation of eggs, and hatching of larvae. For many Asian stocks these events occur in the lower half of the temperature range; with North American stocks they tend to occur in the upper half of the range. In British Columbia waters, salinities associated with these events (range, optimum) are spawning (2.6–28.7‰, 27–28.7‰), [Formula: see text] fertilization of eggs (4.5–42‰, 12–15‰), and maximum total hatch and hatch of viable larvae (4.5–42‰, 12–17‰). A low/low–high/high interaction between salinity and temperature also influences total hatch, hatch of viable larvae, and salinity tolerance of larvae. In addition, the following implications arise regarding aspects of the Pacific herring reproductive cycle, based on previously published and new data, and on speculative inference. The response of Pacific herring to salinity and temperature appears to have a commanding influence on the reproductive cycle and, thereby, on distribution of the species. Survival of eggs on substrate, related to respiratory activity, appears to be influenced by the transport and perfusion velocity of interstitial water in an egg mass. Such transport may involve perivitelline fluid colloid osmotic pressure; natural convection; the surge associated with wave action, beach slope, and depth; and possibly differences in resistance to convective flow of deoxygenated water from an egg mass based on orientation of the substrate. These relations would be modified by variations in deposition intensity (number of egg layers) and packing density (eggs per unit volume), and both factors may affect survival of occluded eggs in an egg mass differentially, depending on the substrate used. A review of data on salinity tolerance of herring larvae indicates that a variety of dosage-mortality techiques has been used, leading to noncomparable estimates of response. An assessment of upper incipient lethal salinities will require standardization of such techniques. Recent studies show that salinity tolerance of larvae is influenced significantly by salinity–temperature conditions during egg incubation. At usual incubation conditions in British Columbia waters, the upper boundary of larval tolerance is estimated as 27.5–31.7‰ S (72-h LC10). depending on incubation history. The fate of Pacific herring larvae carried into the higher salinities of offshore waters has been controversial. In the Strait of Georgia, British Columbia, substantial offshore dispersion of larvae occurs where surface conditions generally are 27–28.6‰ and 9–10 °C in the early larval period. Although these salinities are near the upper boundary of salinity tolerance, larvae sampled in offshore waters (1981) had an apparent mean age of 15 d and were actively feeding and growing. From rates of disappearance of larvae in the offshore waters (9% wk) and inshore waters (45% wk) we conclude that usual surface salinities and food supply in the open waters of the Strait were not a dominant influence on larval survival. Assuming the larvae remain in the upper 10 m, we suspect their disappearance, at least offshore, to be largely the result of predation.

Laboratory observations indicate that spawning of Pacific herring (Clupea harengus pallasi) involves very similar if not identical behavior in males and females, and no identifiable behavioral interactions between the sexes. The presence of a sexual pheromone in herring milt is indicated because spawning behavior is rapidly initiated in ripe (ovulated and spermiated) herring of either sex following exposure either to herring milt or to a filtrate of ripe herring testes. Exposure to herring eggs or to filtrates of hake (Merluccius productus) or Pacific cod (Gadus macrocephalus) testes did not elicit such responses. Four components of spawning behavior induced by herring testis filtrate are identified and described: rising and milling, papilla extension, substrate testing, and substrate spawning. Testis filtrates also elicited rising and milling in spent, developing, and mature (unovulated and unspermiated) fish but rising was not followed by papilla extension, substrate testing, or substrate spawning in fish at these earlier stages of gonadal development. Herring at all stages of maturity also displayed rising and milling in response to an olfactory stimulus (filtrate of crushed euphausiids). This feeding response was weakest in the mature and ripe stages, when fish under natural conditions are reported not to feed, and was strongest in the spent stage, when wild fish resume feeding. In terms of the common components of the response to testis and euphausid filtrates (increased swimming speed, rising, and milling), differential responses to these two stimuli were seen only in ripe fish, suggesting herring at other stages of gonadal development may simply perceive milt as a food stimulus.Key words: Clupea harengus pallasi, spawning behavior, pheromone, feeding

Pacific herring (Clupea harengus pallasi) spawn in southern British Columbia was surveyed by divers in 1976 and 1978. These surveys showed that the distribution of eggs is dependent on the type of vegetation on which the eggs are laid and on the slope of the beach. Most of the spawn on pure sea grass beds was deposited in the littoral zone. Spawn on mixtures of vegetation types was mostly sublittoral and the areal extent of these spawnings has been underestimated by surface surveys. To obtain a good estimate of egg deposition, diver surveys are required. Red algae were the major vegetation type for the study area, followed by sea grass, rockweed, kelp, and other brown algae. Eggs were deposited deeper as the beach slope became steeper. A small fraction of the total egg complement becomes exposed to air as a result of normal tidal cycles during the incubation period, and egg loss from predation and storms was estimated at 10%.Key words: Pacific herring, spawn, egg distribution, vegetation, depth, beach slope

A complete analytical solution is presented for the problem of finding the common rate of exploitation that maximizes total sustained yield from a mixture of stocks when each stock follows a Ricker reproduction curve. A computer program is described which solves this problem for up to 20 stocks varying in both reproductive potentials and absolute sizes. Some aspects of the management of Pacific salmon and fishing strategies are discussed in relation to the question of obtaining maximum yields when harvesting mixtures of stocks under various constraints.