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Date Posted:07/ 2/03 16:56 Author Host/IP: dialup-109.13.220.203.acc09-dryb-mel.comindico.com.au/203.220.13.109
Research indicates that purse seines caught 80%-90% of the vulnerable migrating salmon present in Johnstone Strait during what were commonly 48- or 72-hour fishing openings.
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." Mr. Meadows, in the December 1981 issue, 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.)
The dissertation (Ledbetter, Max. 1986. Competition and information among British Columbia salmon purse seiners. Ph.D. diss., University of British Columbia, Vancouver, B.C.) is available at the National Library of Canada and UMI (see below). Here is the abstract:
In British Columbia, Canada, salmon purse seiners line up at fishing access points, forming well defined queues. These queues were measured over time in Johnstone Strait using a one-dimensional recording scale. Sixty-one overflights of the fishing area were attempted; 51 flights were completed.
Two models were presented for exploitation rates in relation to queuing patterns. The overflight model was based upon the line-up distributions, and assumed that information was good (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 Strait during what were commonly 48- or 72-hour fishing openings.
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.
Ledbetter, Max. 1986. Competition and information among British Columbia salmon purse seiners. Ph.D. diss., University of British Columbia, Vancouver, B.C.
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Aerial Surveillance: The British Columbia Salmon Fleet