In general, improvements are needed on theoretical escapement management techniques, escapement goal setting methods, and escapement and run size data quality. There is also a need to change managers’ and harvesters’ expectations to coincide with the natural variation and uncertainty in the abundance of salmon populations. All the recommendations are aimed at optimizing the number of spawners - healthy escapements ensure salmon sustainability by providing eggs for future production, nutrients to the system, and genetic diversity.
So one of the major flaws in salmon population models is that they assume a constant carrying capacity. To make matters worse, low escapements may be further diminished by the decreasing number of carcasses in the stream. Recent research demonstrates that a large proportion of productivity in healthy salmon streams is derived from nutrients in decaying salmon carcasses. As the number of carcasses decreases, so does the biological carrying capacity, even when physical habitat is in good condition. If the physical habitat is simultaneously being degraded, it is impossible to discern whether the relative carrying capacity reductions are due to habitat degradation, lack of carcass transported nutrients, or both.
What would production be like if escapements were of historic magnitude, i.e., about ten or more times greater than today’s? Of course, this unrealistically assumes pristine freshwater carrying capacity. However, since it is unlikely that freshwater habitat quality has been reduced 90% coastwide, as escapements have, ideal contemporary escapement goals probably lie somewhere between those observed today and ten times as much.
Escapement goals have not been established at all for 192 U.S. management units (22%). Together, this assessment shows that far too many management units are being managed with inappropriate, weak, or no goals.
To achieve fisheries sustainability, the methods for setting escapement goals must be improved. With 80% of management units having goals developed by fair or poor methods or having no goal, there is clearly a serious problem with the salmon management system.
An example of such a downward trend is the Klamath River chinook salmon, well documented in the beginning of its negative spiral by Fraidenburg and Lincoln (1985). As of 1978, the first year for which basin-wide escapement estimates were available, the escapement goal was 115,000 spawners, most of which were wild. In response to drought and overfishing, the Pacific Fishery Management Council (PFMC) adopted a 1980 interim escapement goal of 86,000 to prevent disruption of troll fisheries and cited a commitment to return to the original goal within 4 years. By 1983, PFMC had, in response to cries of economic hardship from user groups, adjusted the inriver run size target (escapement plus inriver catch) to 68,900 and the rebuilding schedule was lengthened to 16 years. Over the past few years, the escapement floor has been reduced to 35,000 with inriver run size (escapement plus inriver catch) targets set annually ö in 1995 the target was 75,200. The 1995 escapement exceeded the floor for the first time since 1989. While this case provides an excellent example of how politics has influenced salmon management, it also illustrates how scientists and managers sometimes participate in regulating a fishery into overfishing.
Over 44% of 9430 identified populations or 2925 populations for which there is information are not monitored for escapement. Escapement data collection was rated as excellent for 79 U.S. populations (1%), rated good for 54 populations (1%), rated fair for 114 populations (2%), and rated poor for 3,441 populations (52%).
·it remains obvious that both escapement data collection methods and the programs to collect high quality escapement information are deficient. It is interesting to note that, while the National Research Council (1996) recommended adoption of a minimum sustainable escapement (MSE) approach and recommended more spawners in streams, they only indirectly alluded to the dearth of good quality escapement data essential for understanding the health of populations. Without improvements in the escapement monitoring system, achieving the laudable goals of MSE will be nearly impossible for many populations.
Alaska Department of Fish and Game sets one escapement goal for Kasilof River sockeye salmon and manages based on a spawner/recruit relationship. However, recent studies are beginning to reveal that the Kasilof system sockeye run actually consists of several biologically unique populations. A critical looming question in this and other similar cases is whether, having this new knowledge about smaller population units, harvest management could or should be changed to ensure abundance and biodiversity of all the populations.
To achieve overall sustainability, it is always preferable to identify likely spawning aggregations as the smallest population unit, try to assess productivity at that level, and then develop management plans for protecting abundance and genetic diversity based on that knowledge. This does not necessarily rule out mixed population fisheries, but highlights the need for full understanding of the component populations being managed as a unit.
Maximizing harvests of hatchery fish in mixed population fisheries often results in over harvest of wild fish and in large areas of potential salmon habitat being underutilized. Some noteworthy examples include Lower Columbia River coho, Willapa Bay salmon and Nooksack coho salmon.
These recommended actions fall into three general categories: (1) improve the science of, and practical methods for, assessing escapements and setting goals; (2) ensure that escapements are sufficient to perpetuate maximum biomass production and biodiversity; or (3) change public attitudes and expectations about salmon production and fishing.
·scientists and managers should develop new models that better account for natural environmental variability and actual carrying capacity (when the freshwater habitat is fully seeded with carcasses).
Debate will continue on the relevance of discriminating among populations at the finest scale, but I contend the critical question is whether biologically discernable populations have differing productivity rates; if so, they should either be managed separately from neighboring populations or as a group but with a conservative exploitation policy.
We cannot count on repairing only one damaged aspect of salmon runs (e.g., degraded habitat) to fix the problem, but must work on all fronts simultaneously. Ultimately, though, both productivity and biodiversity depend on sufficient escapement of spawners to fully utilize the available freshwater habitat, fertilize the systems with carcasses, and optimize genetic diversity.