The wealth of information about the anchovy population of the California Current was used in the prototype management plan under the Magnuson-Stevens Fishery Conservation and Management Act, and U.S. West coast anchovy are now managed as part of a Coastal Pelegics Species Fishery Management Plan. The anchovy population increase after the collapse of the Pacific sardine was then thought to play a major role in suppressing the recovery of the of the local sardine population. There was no direct knowledge about how this would happen. A broadly based system of laboratory, field micro distribution, and field macro distribution studies allowed description of the anchovy population like no other massive population has been described owing to the work of Lasker, Moser, Hunter, and Smith, their predecessors and their numerous associates, post-doctoral students and under-graduate and graduate students (Lasker 1981). The environment of this species is quite well known for the latter half of the 20th Century owing to the continuing work of CalCOFI(Hewitt 1988) and the discontinued work of the University of California Institute of Marine Sciences Food Chain Research Group (Eppley 1986). The Northern Anchovy is an underutilized species (Shimada et al. 1999, Leet et al. 1992) with a long term potential yield of 120,000 tons. Peak yield was 140,000 metric tons in 1975.
The importance of the microbial loop to the early life history of anchovy was described by Lasker et al. (1970) and quantitatively assessed by Hunter (1972). The early life history was marked by radical changes in environmental requirements from the simple embryo persisting on yolk to the first feeding larva stage which required large numbers of motile organisms in each milliliter of its environment. Later stages required mesoplankton species until, at the age of 2-3 months the larva metamorphosed from a carnivorous larva to an omnivorous juvenile with a well developed filtering apparatus as well as predatory behavior.
Field Micro Distribution
Lasker (1975) extended the laboratory studies by an ingenious experiment. Lasker took reared anchovy larvae from the laboratory to sea to perform assays of the esculent particles, usually live naked dinoflagellates. Known as the 'stable ocean hypothesis' it was established that anchovy larvae could survive and grow only in fine strata in the water column when long periods of calm weather allowed the ocean to stabilize. The aggregations of motile phytoplankton were fostered and maintained for periods of time sufficient for the larvae to develop through the week-long 'first feeding' life stage.
Field Macro Distribution
With massive assistance from California Department of Fish and Game, the field macro distribution of anchovy is well known for the decade of the 70's. The fundamental structure is the school group of 10's to 100's kilometers with 1 to 10 thousand schools of anchovies at all ages and mixtures of other pelagic schooling fish and their predators. The schools themselves appear to be assemblies of fish with similar swimming ability. Within some schools there are cliques made up of ten to twenty percent of the mature females ready for contemporary spawning on a given night and their coterie of males. Within the general habitat, the schools cover somewhat less than 1 percent of the sea surface area.
A most amazing event followed the ENSO of 1982-3. The subsequent cold event may have allowed the introduction of a small fraction of the Pacific anchovies into the Gulf of California where they reproduced to become a major stock in the gulf after a century of absence. They were detected in the gulf fisheries, a sequence of larval fish surveys and egg production cruises and a contemporary analysis of stomach analyses of larvae, juvenile and adults in the nesting bird populations of the central gulf.
Moser and Pommeranz (1999) afforded crucial detail about the vertical distribution of anchovy eggs and larvae. Their work confirmed the earlier work of Ahlstrom (1959) describing the shallow habitat depth for the egg and larval stages of anchovy. About 95% of eggs and 90% of larvae were located in the upper 30 meters of the water column. This landmark work will support abundance indices derived from surface pumping, and also support mathematical models of trophic interactions of anchovy with principle food species, predators and competitors.
Holliday and Larson (1979) described the thickness and vertical distribution of schooled adults over the continental shelf. The median thickness of schools was 4 m but extended to nearly 20 m at times. Depths of this small sample of schools was predominately in the upper 40 meters.
Smith (1970) described the horizontal size distribution of anchovy schools in the Southern California Bight. Mais (1974) described a far larger set of schools over the coastal region of California and Baja California Mexico. Hewitt et al. (1976) described the independence of anchovy school distribution from the bottom depths of the shelf, slope, basins of the Southern California Bight. The schools appear to be organized into school groups (Mais 1974). Smith et al. (1989) compared the distribution of sizes of fish schools and school groups relative to plankton patches and gaps. The distributions were from historical records, not contemporaneous as they would have to be for analytical purposes.