Pacific sardine (Sardinops sagax) COSEWIC assessment and status report: chapter 8

Limiting Factors and Threats

The factors determining the abundance of the sardine are not well understood. It is known that reproductive success or survival to recruitment is linked to water temperature (Conser et al. 2001). Historically, an intensive fishery had dramatic effects on the abundance of sardines. Additionally, there have been speculations about the interrelationships of the sardine and anchovy populations both on short and long time scales from examinations of sediment cores (Soutar and Isaacs 1969, 1974). These data suggest that anchovy have been present in the offshore California area for at least the past 200 years at a more uniform level of abundance than the Pacific sardine (Soutar and Isaacs 1974). During this time period, the sardine appears to have had periods of great abundance interspersed with almost complete absence. It is possible that the sardine is locally adapted to a narrower range of temperature for spawning, and subsequent egg and larval development and survival, than the anchovy. Thus, long- term changes in ocean temperature regimes would affect the success of reproduction and ultimately stock size to the extent that the sardine would be a successful competitor with anchovy in restricted areas, as the latter appears to be more tolerant of a wider range in temperature. The limiting factor to the current expansion of the sardine population may be the availability of spawning habitat and food, as the population begins to saturate its available resource base.

The fishery management regime currently in place in the United States for sardines allows for a maximum 15% harvest rate. This rate may vary between 5-15 % and islinked to recent water temperature, which directly determines reproductive success and productivity of the species. This harvest rate policy is thought to be precautionary and approximates the maximum sustainable harvest rate estimated for this species. In addition, the harvest policy includes the requirement for a spawning reserve of 150,000 metric tonnes that is protected prior to considering any fisheries (Conser et al. 2001).

At present, there is only an experimental fishery for sardine in British Columbia but there is interest in its expansion. The proposed Canadian harvest rate is fixed at the United States rate and the harvest would be based on the US assessment of the population size (Schweigert and McFarlane, 2001). Since the Canadian fishery is based on northward migrants from California, a very limited portion of the population is susceptible to exploitation here, and at the proposed harvest rate would amount to only 1-2% of the entire stock. This assumes that 10% of the population migrates into Canadian waters and 5-15% of these fish are captured.

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