By Misha Warbanski
[Former public radio reporter Misha Warbanski studies biology at the University of Victoria in British Columbia, Canada.]
Pacific sardine (Sardinops sagax) is a small pelagic schooling fish that can live up to 15 years and reach 41cms in length. Its range stretches over 5,000km of coastal surface waters, from Baja California to Southern Alaska, traveling up to 300km offshore. In recent years, researchers have looked at ecological and environmental factors to better explain the dramatic declines and reappearances of the species. Using scales preserved in sediment cores, scientists traced patterns of Pacific sardine abundance from 300AD to the 1970s. Sardine populations are characterized by cyclic patterns of boom and bust, averaging 60 years.
From the mid-1920s until the late-1940s, the Pacific sardine made up the most important fishery on the west coast of North America. A century earlier, the small forage fish, also known as pilchard, bore little mention. Extolling the riches of the west coast fishing, an 1858 dispatch from San Francisco in the New York Tribune had only this to say about sardine:
… the cod, halibut, herring, salmon, smelt, sturgeon are abundant, and are easily caught, while a large market is ready to buy them at a high price […] A small fish called the “sardine”, supposed by many to be a species of herring, is abundant, but not much value is commonly attached to it.”
Attention turned to sardine in response to food shortages during World War I. Sardine was rendered for oil, canned for food and also used for bait in other fisheries. At its peak, fishermen hauled in more than 700,000 tons of sardine, well above recent Canadian catch. In BC, fish plants in Kyuquot and Barkley Sound employed many, but by the end of the Second World War, sardine stocks were in precipitous decline. The fish disappeared from BC waters in 1947, and their range had retracted south to Monterey Bay by 1952.
Pointing the finger at overfishing, the Canada’s Committee on the Status of Endangered Wildlife in Canada (COSEWIC) listed Pacific sardine as a species of concern in 1987. But in the summer of 1992, after a half-century of collapse, the sardines were back, initially turning up as by-catch in trawl surveys for juvenile salmon and Pacific herring. Canada’s Department of Fisheries and Oceans opened a cautious trial fishery in 2003. But by the fall of 2013, newspapers announced that the “sardine seine fleet has gone home after failing to catch a single fish.” The fishery had once again collapsed, “inexplicably and completely.”
Recovery or decline? In newspapers and on talk radio, the failure of the 2013 fishery was painted as a surprise. Just ten years into commercial fishing, the species had once again vanished. The DFO’s 2013 updated fishing guidelines projected stability in the “short and medium term.” But based on literature reviews and acoustic trawl surveys, Zwolinski and Demer predicted the collapse. Predictions were based on declining Chilean and Japanese stocks, cool water temperatures due to a negative phase of the Pacific Decadal Oscillation, and increases in mackerel abundance. The researchers were critical of Canada’s decision to increase the migration estimate from 10 to 18 per cent, since it effectively increased allowable catch by 80%. [There is, however, disagreement in the literature over exploitation rates. Zwolinski and Demer report a 25% exploitation rate, while Canadian authorities report realized exploitation between 0.1 and 3.7% (Flostrand et al., 2011).]
Historic pacific sardine catch trends suggest the latest recovery may not have been as strong as the previous cycle of abundance. Some researchers recommend using climate modeling to better inform management decisions. Many continue to dismiss the relevance of overfishing. However a critical look at why Canadian catch quotas remained high against declining stocks bears further examination.
Figure 1. Pacific sardine was an important fishery from the mid-1920s until 1947. They returned to Canadian waters in 1992 only to disappear again in 2013. (Data compiled from Hill et al., 2012; DFO, 2013; McFarland & Beamish, 2001)