Salmon Fishing Brings on Hard Competition

Author: M. Ledbetter

Some might recall Al Meadow's comments (Cockpit Comments. Western Fisheries 102 (August 1981): 28): ""I'll be reviewing a study known as the Ledbetter Report in a future comment. This report is about the seine boat fishery in Johnstone Strait and I have heard disturbing news that the Fisheries Service is attempting to water down and suppress it."" In the December 1981 issue of Western Fisheries, Mr. Meadows continued, ""Max Ledbetter, writing in the guest editorial section of the October issue, is, I feel, pulling some punches and not telling the full story. He is, however, absolutely correct in his summation, where he suggests that fishermen had better develop communication amongst themselves and their various gear types. Recent history has shown us, and the fact that wild chinook and coho are on the verge of extinction further reinforces the realization that we cannot depend on the D.F.O. to do the job"" (Cockpit Comments. Western Fisheries 103 (December 1981): 11).

Later, towards the end of the twentieth century, Pascual and Quinn reported, ""The best available information about the spatial distribution of sockeye salmon in this area [Johnstone Strait] comes from experimental fishing cruises performed in 1985 and 1986 (Cooke et al. 1987) and surveys of the distribution of fishing effort (Ledbetter 198[6])."" (See Pascual, M. A. and T. P. Quinn. 1991. Canadian Journal of Fisheries and Aquatic Sciences 48: 799-810, and my dissertation, Ledbetter, Max. 1986. University of British Columbia.)

In British Columbia, Canada, salmon purse seiners line up at fishing access points, forming well defined queues. These queues were measured over time, using a one-dimensional recording scale. Sixty-one overflights of Johnstone Strait and Queen Charlotte Strait were attempted; 51 flights were completed.

Two models were presented for exploitation rates in relation to queuing patterns. The overflight model was fit to the line-up distributions. One underlying assumption was that the skippers possessed fairly accurate information regarding the distribution of catches (analysis of variance methods utilizing skippers' logbook data showed that line-up lengths reflected catch rates). The model fit well and the parameter estimates reflected anecdotal and statistical information about fish behavior. The exploitation rates saturated at an effort level of 100 vessels (whereas the maximum effort observed was 363 boats) and indicated that (at saturation) the fleet caught 80% to 90% of the vulnerable migrating salmon present in Johnstone and Queen Charlotte Straits during what were commonly 48- or 72-hour fishing openings. (Note: Salmon successfully migrating through the strait on days that were closed to seiners and salmon that were not vulnerable to the gear--e.g., below the depth of the nets--escaped the purse-seine fleet.)

In general, traditional assumptions were rejected. Vessels did not operate independently. Boats were not distributed in a random fashion. The overflight model provided predicted exploitation rates. The exploitation response to effort was qualitatively distinct from the forms incorporated in traditional models.

In partial summary, the question is one of fishing power--the ability of gear, boats, or fleets, in the B.C. and P.E.I. cases and others, to exploit or overexploit fish stocks. Without a historical perspective based on quantitative (and innovative) field research, we are doomed to repeat our work loads: In the absence of extensive (and often necessarily alternative) time series of fishing effort and effectivity (fishing power), stock assessment and fisheries management become absurd. Like they said on P.E.I., a fleet (or transient cluster) of purse seiners can wipe out a stock (anywhere in the world).

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