Burkett 



Chapter 22 



Food Habits and Prey Ecology 



Marine communities have been altered by the activities 

 of humans in conjunction with natural influences (Caims 

 1992a: 39). As early as 1886, declines in fish populations in 

 heavily fished areas seemed apparent. The notes of an 

 expedition to Puget Sound in July 1895 contained the 

 following anecdote regarding herring: "Exceedingly abundant. 

 J.P. Hammand (American Angler. December 18, 1886) states 

 that from 1 8-25 years ago it was not an uncommon occurrence 

 for a 'gang' of fishermen to catch from 200-300 barrels of 

 herring in a night on Puget Sound. Now the largest night's 

 work is 20 barrels" (Jordan and Starks 18%). The sardine 

 fishery in California which was discussed above is another 

 example. The relatively new fishery went from the "palmiest 

 days" of Cannery Row in the mid-1930's to a catastrophic 

 drop in 1947. In response to this drastic decline, there emerged 

 what is known today as the California Cooperative Oceanic 

 Fisheries Investigations (CalCOFI) program to help better 

 manage marine resources (Ricketts and Calvin 1962: 382). 

 The observations of Radovich (1961) are helpful: "The mere 

 fact one can demonstrate the environment has a large effect 

 on the catch does not imply man's effect is inconsequential. 

 To understand man's effect, one must study the effect of 

 man. However, a satisfactory understanding may never be 

 achieved so long as one fails to recognize the existence of 

 some of the other factors constantly confusing his data. The 

 effects of environment and man on fish populations are not 

 mutually exclusive." The long history of fishing activity in 

 the North Sea produced steep declines followed by increases 

 when fishing pressure diminished. Such events resulted in 

 Sir Alister Hardy's remark: "Certainly no one can deny that 

 over-fishing exists; we must find the best way to remedy it" 

 (Hardy 196"5: 247-248). 



The scale-deposition studies described above provide 

 evidence that abundance of coastal pelagic fish species varied 

 considerably before the inception of modern fisheries. 

 Environmental factors and trophic-level interactions contribute 

 to the naturally dynamic state of marine ecosystems. Fishing 

 has. however, probably exacerbated the natural variability in 

 recent decades because reduced stock size and loss of old 

 fish, which is an inescapable result of fishing, increase the 

 speed and magnitude of population decreases during periods 

 of poor reproduction. Approaches to fishery management 

 based on equilibrium or steady-state concepts that ignore 

 variability in abundance have a long history of failure for 

 coastal pelagic species in many regions of the world (Troadec 

 and others in Anonymous 1993). Managers should expect 

 considerable interannual variation in abundance and yields 

 and should curtail fisheries to protect the long-term health of 

 the stock when necessary. Chaotic ecosystems appear to 

 require reliance on management that is beneficially adaptive 

 rather than manipulative. The possibility of detailed predictions 

 is effectively ruled out. and many factors, including 

 socioeconomic ones, must be used when modeling populations, 

 ecosystems, and fishery impacts (Wilson and others 1991). 



Throughout its range, the murrelet consumes a very 

 diverse group of prey resources, especially when one considers 



the limited studies which have been done to date. This 

 indicates great flexibility in prey choice and a high capability 

 for prey-switching behavior. This would make adaptive sense 

 given the multiple factors affecting prey availability each 

 year and the oceanographic differences found offshore from 

 forest nesting habitat throughout the range of the species. It 

 also indicates that El Nino events would not be expected to 

 cause catastrophic population fluctuations or declines, 

 especially in the long term. Given the variability in frequency 

 and intensity of El Nino events, murrelet production could 

 be lower than "normal" in some years as has been 

 demonstrated for many other seabirds. But, like odier seabirds, 

 the murrelet has evolved with this phenomenon and can 

 likely change its foraging behavior and food preferences to 

 some degree in order to utilize available resources (Carter 

 1984, Croll 1990, Krasnow and Sanger 1982, Sanger 1987b, 

 Sealy 1975c). Additionally, the long life span of the species 

 allows for adequate reproduction and dynamic equilibrium 

 of the population, even in the face of low reproduction in 

 some years. However, cumulative impacts in localized areas 

 over a short time period could cause serious population 

 declines or possibly even extirpations. 



Research should continue to identify bottlenecks to 

 recovery; "scientifically approachable" and "practically 

 realizable" studies should be done along with attempts at 

 "integrated management of the marine ecosystem as a whole" 

 (Holt 1993). A lack of information on the functioning of 

 "natural systems" (Willers 1993) should not prevent 

 comprehensive research or recovery actions in the future, 

 but instead should help guide more unified study efforts. 

 Biologists have long recognized the need to integrate seabird 

 and marine science (Ainley and Sanger 1979, Furness 1984, 

 Munro and Clemens 1931, Sealy 1990, and others) and the 

 excellent treatise on the matter by Cairns (1992b) should 

 help guide marine ecosystem research and management in 

 the future. 



Managers and researchers today are faced with the listed 

 or sensitive management status of the murrelet and limited 

 financial resources to conduct the necessary studies. It is 

 now more important than ever to pool resources and seek 

 innovative ways to conduct the necessary research. Mitigation 

 banking policies imposed on commercial fishing and timber 

 industries, coupled with damage assessment rewards, could 

 help gather research funds and support the large-scale studies 

 proposed by Nisbet (1979) and Vermeer (1992). Research 

 monies alone are not recognized as adequate mitigation for 

 negative impacts to natural resources, but funds derived 

 from such policies could certainly play a stronger role in the 

 conservation and recovery of the murrelet than has occurred 

 up to this point 



These ideas are not new (Drury 1979, Nisbet 1979), but 

 implementation has yet to occur on a meaningful scale. In 

 the words of Drury (1979: 136): "Experience in Europe and 

 in New England suggests that if reasonable limitations are 

 set on human activities and that if adequate money charge is 

 made against those who profit by economic development to 



USDA Forest Service Gen. Tech. Rep. PSW-152. 1995. 



245 



