215 



DRAFT 



"Applying a shaker mortality of this value [30 to 40 percent] to the 

 582,000 salmon landed in Oregon during the 1990 ocean commercial 

 troll and recreational fisheries adds an additional mortality of 174,400 

 to 232,500 fish to the 1990 ocean population (Table 1. 1-24). " 



This analysis is erroneous. Shaker mortality estimates apply to the loss of fish that are 

 encountered and released in a fishery, and cannot be applied to estimate the fish lost as 

 a proportion of the total landings. Shaker mortality estimates are only applied to the 

 number of fish encountered and released. They cannot be estimated without first 

 estimating the number of sublegal fish or non-target species encountered by a fishery. 

 For the author's estimates to be accurate {174,400 to 232,500), the fisheries would 

 have needed to encounter and release 582,000 salmon (assuming that 30 to 40 percent 

 shaker mortalities are accurate). 



Applying estimates of shaker mortality to total fish landings greatly over-estimates the 

 loss of salmonids. For example, if a troll fishery harvestwl 100,000 legal fish in a 

 season and encountered and released an additional 50,000 fish, applying a 30 percent 

 shaker mortality rate to the total landing s would estimate a loss of 30,000 additional 

 fish. In actuality, the loss would be 15,000 fish (30 percent of 50,000). In the 

 previous example of PFMC shaker mortality estimates (30 to 26 percent, by gear type), 

 the hooking loss estimates are applied to estimates of the number of fish encountered 

 and released by the fishery, not to the total landings. 



The authors erroneously apply a generic range of mortality estimates derived from 

 commercial troll fisheries to the estimate of total 1990 landings that includes harvest by 

 recreational anglers. Commercial and recreational ocean salmon fisheries differ greatly 

 in fishing methods and gear. It is inaccurate to apply mortality estimates from 

 commercial fisheries to recreational salmon landings. 



To correctly estimate the incidental loss of salmonids during ocean fisheries, the 

 authors should ensure that: (1) the appropriate type of fishing mortality estimate is 

 being used, (2) fishery data is stratified by angler-type (commercial versus 

 recreational), (3) estimates are stratified by gear-types (barbed versus barbless hooks, 

 etc.)^4) mortality estimates are stratified by species, and (5) other factors such as 

 fishery location, time of the year, encounter rates for non-target species and sublegal 

 fish, etc. are considered. 



Dropout Mortality (page 23) 



'. . . it seems reasonable to assume an annual dropout mortality rate of 

 between 4 and 8 percent for the Columbia River commercial net fishery. " 



The authors estimate these dropout mortality losses based upon information from the 

 Klamath River tribal fishery, and the Puget Sound gill-net fishery. There have been no 

 studies of gillnet dropout in the Columbia River to substantiate these estimates. Gillnet 

 dropout is believed by ODFW to be low in the Columbia River fishery, and the 

 mortality rate varies considerably by fish species, gillnet type, and by time of the year. 

 The authors do not account for this variability, and do not state whether the fisheries 

 evaluated for the dropout mortality estimates were conducted with similar gear, under 

 similar environmental conditions, or targeted similar sizes and species of salmonids. 



A-9 



