Burkett 



Chapter 22 



Food Habits and Prey Ecology 



study and advised that a close watch of the situation was in 

 order because of declining anchovy populations. 



Anderson and others (1980) proposed the establishment 

 of protected foraging zones as critical habitat under the 

 federal Endangered Species Act in order to assure adequate 

 pelican reproduction and conservation. However, they 

 recognized that because of the unpredictable nature of anchovy 

 distribution, such areas could be difficult to define between 

 seasons and between years. Protection of marine habitat as 

 critical habitat for the murrelet has also been recommended 

 by researchers, the Marbled Murrelet Recovery Team, and 

 the California Department of Fish and Game. 



Pacific Sardine 



These small pelagic clupeids occur in the California 

 Current system from southern Baja California to southeastern 

 Alaska, and in the Gulf of California. In the northern portion 

 of the range, occurrence is seasonal. It has been generally 

 accepted that the sardine population off the west coast of 

 North America consists of three subpopulations. A northern 

 subpopulation (northern Baja California to Alaska), a 

 southern subpopulation (off Baja California), and a Gulf of 

 California subpopulation were distinguished on the basis of 

 serological techniques (Vrooman in Anonymous 1993). 



Historically, the sardines migrated extensively, moving 

 north as far as British Columbia in the summer and returning 

 to southern California and northern Baja California in the 

 fall. The migration was complex, and timing and extent of 

 movement were affected to some degree by oceanographic 

 conditions (Hart in Anonymous 1993). 



Sardines reach about 41 cm in length, but usually are 

 shorter than 30 cm. They live as long as 1 3 years, although 

 most sardines in the historical and current commercial catch 

 are 5 years and younger. They spawn in loosely aggregated 

 schools in the upper 50 meters of the water column probably 

 year-round, with peaks from April to August. Spawning 

 has been observed off Oregon, and young fish have been 

 seen in waters off British Columbia, but these were probably 

 sporadic occurrences (Ahlstrom in Anonymous 1993). The 

 spatial and seasonal distribution of spawning is influenced 

 by temperature. 



Sardines prey on crustaceans, mostly copepods, and 

 consume other phytoplankton, including fish larvae. Larval 

 sardines feed extensively on the eggs, larvae, and juvenile 

 stages of copepods, as well as on other phytoplankton 

 and zooplankton. 



The fishery began in central California in the late 1800's 

 and developed in response to a demand for food during 

 World War I (Schaefer and others in Wolf 1992). The 

 Pacific sardine supported the largest fishery in the Western 

 Hemisphere during the 1930's and 1940's, with landings in 

 British Columbia, Washington, Oregon, California, and 

 Mexico. The fishery declined, beginning in the late 1940's 

 and with some short-term reversals, to extremely low levels 

 in the 1970's. There was a southward shift as the fishery 

 decreased, with landings ceasing in the northwest in 1947- 



1948, and in San Francisco in 1951-1952. The regulatory 

 history of the sardine fishery might best be described as 

 "too little too late." Regulatory authority for the sardine 

 fishery in California rested with the legislature, which 

 delegated only limited authority to the Fish and Game 

 Commission. State biologists had expressed concern about 

 the size of the fishery as early as 1930. Industry opposed 

 any regulation of total catch, and an intense debate began 

 over whether the decline of the sardine fishery and population 

 was due to overfishing or environmental factors (Clark and 

 Marr in Wolf 1992). 



It was not until 1967, well after the fishery had collapsed, 

 that the California legislature passed an "emergency" bill 

 declaring a 2-year moratorium on fishing sardines, and in 

 1974 another bill was enacted which established a complete 

 moratorium on directed fishing for sardines, though an 

 incidental catch provision continued. A small directed fishery 

 was first allowed in 1986 and the directed quota has recently 

 been enlarged (Wolf 1992). 



Since the early 1980's, sardines have been taken 

 incidentally with Pacific (Scomber japonicus) and jack 

 mackerel (Trachurus symmetricus) in the southern California 

 mackerel fishery and primarily canned for pet food, although 

 some were canned for human consumption. Sardines landed 

 in the directed sardine fisheries off California are primarily 

 canned for human consumption and sold overseas. 



Management of the sardine is difficult in the absence of a 

 large fishery since a precise, direct estimate of a relatively 

 small biomass is difficult and expensive to obtain (Wolf 

 1992). Integrated methods of stock assessment will be necessary 

 to manage this resource (Barnes and others 1992). 



Baumgartner and others (1992) presented a composite 

 time series of anchovy and Pacific sardine fish-scale- 

 deposition rates which they developed from sampling the 

 anaerobic layered sediments of the Santa Barbara Basin off 

 southern California. Other researchers (Soutar; and Soutar 

 and Isaacs in Baumgartner and others 1992) had previously 

 collected information on the deposition rates of these species, 

 but their sample sizes were limited and there was uncertainty 

 in the underlying chronology because of imperfect 

 preservation of the annually deposited layers. The new 

 sardine and anchovy series provide significantly more 

 reliable estimates of the scale-deposition rates (SDR's) 

 (Baumgartner and others 1992). An overriding lesson from 

 the Santa Barbara records is that in the past both sardines 

 and anchovies experienced large natural fluctuations which 

 were clearly unrelated to fishing, and that abrupt natural 

 declines, similar to the collapse of the sardines during the 

 1940's, are not uncommon. 



The scale-deposition record shows nine major recoveries 

 and subsequent collapses of the sardine population over the 

 past 1,700 years. The average time for a recovery of the 

 sardine is 30 years. Sardines and anchovies both tend to vary 

 over a period of approximately 60 years. In addition, the 

 anchovies fluctuate at a period of 100 years. There is a 

 moderate correlation between sardines and anchovies over 



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