Email 2 from Leon Shaul more on coho fish tags

Larry, you are welcome to post it or this response too for that matter. The question of defining stocks or management units is an interesting one. I haven't seen a publication yet, but understand that the recent DNA work suggests combining a wide area of the upper Skeena (high interior, Bulkley, Babine) coho into one stock. Certainly, there is alot of movement of juveniles and adults within a watershed and at some point there are no differences between nearby tributaries with similar habitat. However, we can even see clear differences in the fishery distribution of Babine and Toboggan coho even within Alaskan waters (Babine coho tend to be caught later and farther north). Coho are in one sense very plastic and adaptable but there is also alot of diversity within an area like the upper Skeena that has to have some genetic basis. There seems to be a public perception that the policy question for upper Skeena coho is "What to save from extinction and how?" For some, the answer is "everything" and "by completely avoiding harvest of coho". After pouring over the data and talking with observers of salmon and habitat in the drainage for the past 2 years, I think extinction even of a small scale is very unlikely at continued average escapement levels of the past 20 years, with the possible exception of specific cases like the upper Bulkley where the run is now very low for habitat reasons (and where fishery management can likely do little if anything to remedy it). Everything considered, establishment of goals for major tributaries like Babine and Bulkley-Morice (where there is now an excellent mark-recapture program at Moricetown falls) would probably provide the most appropriate management objectives, at least for fisheries up to those points in the system. That level of detail should provide a high probability of maintaining subpopulations in all suitable rearing habitats without unduely driving fishery management from isolated habitat-impaired tributaries where fish are probably not genetically distinct from the rest of the drainage.

Certainly, the number and complexity of wild coho stocks is mind-boggling. When I first starting working on our few wild indicator stocks here 19 years ago, I had trouble seeing how our research on a handful of populations out of thousands would provide enough information to be of much use to management. While our managers were trying to actively manage the troll fleet for coho escapement with very little data other than fishery performance, I felt their objective was unachievable (especially given the scarcity of stock information) and initially advocated a more passive "exploitation rate" approach (fixed percentage kill). At about that time, some of the more southern ocean fisheries were operating under the most regressive possible technique - "ceiling management" (fixed kill regardless of abundance). In more recent years, Canadian managers have moved more to exploitation rate objectives. This is in fact the preferable approach if you have no reliable real-time information on stock abundance for management. However, the southern B.C. coho example shows how it can fail when the environment changes. After a well-documented planning process, the exploitation rate objective for Georgia Strait coho was adjusted downward from 70-80% to 60-70%. Even though the management objective was achieved, escapements plummeted as marine survival dropped in the 1990s. Now the objective has been re-established at 0%. The author of a recent risk assessment for Thompson River coho discusses how much better the escapement situation would likely be if exploitation rates had been reduced concurrent with falling abundance (i.e. fixed escapement objective, not exploitation rate). Your point is exactly right that conservation (i.e. spawning escapement) should be the objective rather than exploitation.

Managers in both Canada and Alaska have done well at inseason management for escapement in cases where it has been both feasible and applied - typically in major single species fisheries. However, there has been a perception that certainly affected me in earlier years (and seems to remain in Canada and southward) that inseason management of coho in ocean fisheries is nearly hopeless, the problems being the huge myriad of stocks with different survival rates and freshwater productivity and a lack of real-time information on abundance. However, what I have found here in Southeast Alaska (and which also appears to be largely true in northern B.C.) is that there is very surprising degree of synchrony of stocks over a broad area and that abundance can be accurately assessed early enough to have substantial control of escapement. Ocean troll fisheries are part of the key to timely information flow rather than simply a management problem. Our troll catch is amazingly well correlated with total run size for our wild coho indicator stocks (even much better than performance of gillnet fisheries right in front of the systems). We have become increasingly confident and reliant on information from the troll fishery (catch rates and tag recoveries) to actively manage the inside fisheries for escapement as well as to determine when the troll fishery itself should be closed or extended. The trollers who encounter coho early, over a broad area and at a wide range of depths are our eyes and ears as fishery managers and we use that information to manage fisheries all the way down the line.

Admittedly, having generally high marine survival in Alaska in recent years has made the management task both easier and more pleasant. It would be a more difficult system to implement for the most southern areas where marine survival has deteriorated to a consistently low trend and where stock productivity is likely more variable (partly because of large and variable human impacts on habitat). There is less room for fisheries of adequate scale to assess abundance in the south. However, I believe the situation in northern B.C. is more similar to Southeast Alaska in that most of the coho harvest is from local wild stocks where habitat is largely intact. Marine survival in the Skeena area, while highly variable from year-to-year still appears to be tracking on a stable long-term trend while areas north and south have trended up and down. The key is responding to the variability to achieve both more stable escapement and higher average fishery benefits. An effective management system requires wild indicator stocks where smolt production, marine survival, catch and escapement are all measured (and biological goals developed). These indicators need to be located to represent the more vulnerable stocks that are likely to have the highest average exploitation rates and lowest inherent productivity. The two key areas in northern B.C. are probably upper Skeena (higher explotation rate, possibly lower freshwater productivity) and Central Coast (lower average marine survival). The Babine and Bulkley areas in the upper Skeena already have fairly good programs and I think I am in agreement with DFO staff that the high interior (upper Skeena-Sustut area) and Central coast are the next priorities. The Charlottes are of interest because the stocks are quite distinctive but are less critical to management because they are likely highly productive coastal stocks and are subjected to less mixed-stock harvest.

Certainly, there are limits to the capability of inseason management. For example, in 1997 there is probably no way even with extensive season-long restrictions throughout the range of the stocks that biological goals for upper Skeena stocks could have been met. However, consider that the 1997 run was probably far and away the smallest in over 50 years and that a responsive inseason management program, while falling short of the goal, certainly would have improved escapement markedly at a time when every spawner would likely have been a benefit to future production. As it is, the 1997 escapement at about a third of the lowest previous low will serve as an experiment in measuring the resilience of the stocks (the measurable results will be known after this season and next). Preliminary evidence from juvenile surveys suggests that overall there may be little effect in most coastal and Skeena tributaries. Sampled juvenile densities in late-summer 1998 were actually above average in some areas including the Babine and only below the recent range in the high interior and upper Bulkley. Because of their protracted freshwater period coho stocks are very susceptable to changes in the freshwater environment but also have a very strong compensatory mechanism that buffers them from variation in spawning escapement. They are typically very susceptable to habitat degradation but resilient under exploitation. In addition, northern coho in particular have the advantage of two freshwater age classes that contribute to a single smolt-adult class. An inherent compensatory increase in survival combined with multiple freshwater ages resulted in an amazingly rapid recovery of the Carnation Creek coho population (west coast of Vancouver Island) from disasterous marine survival in 1993 that resulted in only one female spawner in 1994.

Certainly caution is advised before applying evidence of amazing productivity of coastal coho stocks to widely differing habitats like the interior Skeena drainage. Interior Skeena, Taku and Fraser coho may well be substantially less productive than coastal stocks. However, if the Babine River and Tobaggan Creek populations are a reliable sample, interior Skeena stocks are more than sustainable at average escapement levels of the past 20 years. Estimated MSY (maximum sustained yield) escapement based on spawner-recruit analysis of data from the past 20 years is substantially below the recent average escapement for both stocks. I would be hesitant to recommend goals that low until more is known about other runs in the system. However, the point is that upper Skeena coho stocks are not "a tray of china". They will thrive under management that is responsive to abundance and somewhat conservative (Future exploitation will almost certainly be conservative on average given recent fleet reductions in Canada).

My point in sending the early season prediction of Babine escapement to my collegues last summer was mainly to help demonstrate that inseason management for coho salmon escapement can be done, even though I knew it wasn't possible in 1999 under the immediate policy in effect. The balance of risk that Canadian managers and public are willing to set between conservation and the fisheries is an internal decision that requires more than scientific input. However, the risks to both fishermen and the resource can be reduced to the extent that fisheries can be effectively managed inseason for escapement needs of the more critical stocks. The revised treaty provides not only a directive to develop abundance-based management for biological escapement goals but funding to help make it work. It also provides a specific commitment to manage for northern B.C. coho in Alaska as well as Canada. That's a definite change from 1997 when northern B.C. coho went over the edge with only minor inseason fishery adjustments in either Alaska (escapement goals for Alaskan stocks were achieved) or Canada.