Pacific sardine (Sardinops sagax) COSEWIC assessment and status report: chapter 2

COSEWIC Executive Summary

Pacific Sardine
Sardinops sagax

Species information

The Pacific sardine (Sardinops sagax) resides seasonally in Canadian waters. It migrates northward from California in the spring to the rich feeding grounds off Vancouver Island and returns south in the fall. The evidence from tagging and other studies indicates that sardines venture progressively further north as they age during their annual migration from spawning to feeding areas. The recent consensus on stock structure supports the existence of a single panmictic population in the eastern north Pacific. Intermittent spawning probably occurs in the Pacific Northwest, including British Columbia, but self-sustaining populations are unlikely in this area. Sardines disappeared from Canadian waters in the late 1940s as the entire stock collapsed and only re-appeared in 1992 as the range of the resurgent California population has again expanded.

Distribution

Sardines as a group are classified into three genera and about 18 species world-wide. They are found in the waters of every continent, although they are fundamentally a warm water species whose global distribution is restricted within the latitudes of 60° N and 50° S. The Pacific sardine occurs from northern Mexico to southeastern Alaska, although the main concentration is from southern California - northern Baja to the southern portions of British Columbia.

Habitat

Little is known about specific habitat requirements for the Pacific sardine. In California, sardine schools have been found in temperatures ranging from 7° C to 28° C. The water temperature for spawning is thought to range from 13° to 22° C. Virtually all eggs are found in water between 12.5° and 16° C. The food of the sardine is primarily copepods and diatoms. A combination of water temperatures and favourable feeding conditions may account for the northward migration of adults each summer. Little is known about the requirements of juveniles during their first summer, when they are moved passively inshore and southward by the prevailing currents.

Biology

There are presently two main spawning areas off southern California and Baja California. The major and northern spawning area is between Point Conception and Ensenada. It is about 400 km long and extends up to 325 km offshore. The smaller spawning area, about half the size, is off central Baja California. There is also a smaller spawning area within the Gulf of California. Spawning occurs both in the spring and fall. Adult sardine with ripe eggs have been reported in Canadian waters and juveniles have recently been collected. This is evidence of local spawning. However, the successful recruitment of these juveniles into the population appears to be limited. The Pacific sardines are batch spawners with larger fish (21 cm) releasing up to 65,000 eggs per spawning and up to 200,000 eggs per spawning season. The eggs are pelagic, about 1.6 mm in diameter, and hatch in two to four days. The larvae are about 3.5 mm in length and resorb the yolk sac after four to seven days. Sardines grow rapidly, reaching 115 mm by the end of the first year. The maximum length is 31 cm for a fish 10 to 12 years of age, and females grow faster and larger than males. Young sardines move inshore as they grow and congregate in schools near beaches. Each year, beginning in their second summer, the fish migrate northwards early in summer and travel south again in the fall. The migration extends further north with age. Northward migration may also be affected by oceanographic conditions.

Population sizes and trends

Population sizes and trends in Canada are due to the population dynamics off California and local environmental conditions. Pacific sardines reappeared in Canadian waters in 1992, and are increasing in number. It appears from historical catch records and recent trawl surveys that, on average, about 10% of the US Pacific sardine population migrates into Canada each year. If the US population continues to increase, abundance of sardines in British Columbia should increase proportionately.

Limiting factors and threats

The primary limiting factors and threats to sardine are overfishing and environmental conditions. It is accepted that the collapse of the sardine population in the 1940s was a result of overfishing in combination with unfavourable environmental conditions for sardine survival. The current objective of the US management regime is to harvest only after a minimum spawning stock of 150,000 tonnes exists. A harvest rate of between 5-15%, depending on water temperature, which has been found to relate directly to sardine survival, is presumed to be sustainable. Canada has adopted the US harvest rate and has an interest in expanding the fishery in British Columbia. Without adverse environmental regimes similar to those of the last century, the sardine fishery along the Pacific coast should be sustainable. It has been shown from analyses of sediment cores and scale deposition that this sardine population has collapsed and recovered at least 9 times over the past two millennia, with each period of collapse or recovery lasting about 30 years.

Special significance of the species

Commercial harvesters take sardine as a food and bait species. They have also been an important food source, when available, for Nuu-chah-nulth First Nations people (west coast of Vancouver Island). Sardines are a critical component of ecosystem integrity. They are an important forage species for many other fishes, such as tunas, yellowtail, barracuda, bonito, marlin, hake, and mackerel. During their peak abundance in the 1930s and 1940s, sardines were the dominant prey species for chinook and coho salmon in the Pacific Northwest. The wide distribution of sardine make them readily available prey for mammals such as sea lions, porpoises, whales and birds such as cormorants, gulls, and pelicans.

Existing protection or other status designations

The Pacific sardine is managed in the US under the auspices of the Pacific Fisheries Management Council. The allowable harvest is a function of ocean conditions and stock abundance above a minimum biomass (150,000 mt). The harvest target is believed to be the maximum sustainable yield that is a function of ocean conditions, and is constrained to be between 5 and 15% of the stock forecast to be in US waters. The Pacific sardine in Canadian waters is currently listed by COSEWIC as a species of special concern. It has been managed under an experimental licence by Fisheries and Oceans Canada since 1997, with a harvest of about 1450 tonnes annually.  There is commercial interest in British Columbia to increase this harvest.

COSEWIC Mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) determines the national status of wild species, subspecies, varieties, and nationally significant populations that are considered to be at risk in Canada. Designations are made on all native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fish, lepidopterans, molluscs, vascular plants, lichens, and mosses.

COSEWIC Membership

COSEWIC comprises representatives from each provincial and territorial government wildlife agency, four federal agencies (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biosystematic Partnership), three nonjurisdictional members and the co-chairs of the species specialist groups. The committee meets to consider status reports on candidate species.

Definitions

Species
Any indigenous species, subspecies, variety, or geographically defined population of wild fauna and flora.

Extinct (X)
A species that no longer exists.

Extirpated (XT)
A species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)
A species facing imminent extirpation or extinction.

Threatened (T)
A species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)Footnotea
A species of special concern because of characteristics that make it particularly sensitive to human activities or natural events.

Not at Risk (NAR)Footnoteb
A species that has been evaluated and found to be not at risk.

Data Deficient (DD)Footnotec
A species for which there is insufficient scientific information to support status designation.

 

Canadian Wildlife Service

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.

 

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