Burkett 



Chapter 22 



Food Habits and Prey Ecology 



from south to north. During the spawning season, herring 

 congregate in dense schools and migrate inshore where they 

 deposit their sticky eggs on vegetation found in intertidal 

 and shallow subtidal areas of bays and estuaries. The eggs 

 hatch in about 2 weeks. After spawning, herring return to the 

 open ocean where their movements are largely unknown 

 (Spratt 1981 ). The large herring fisheries are subject to great 

 fluctuations in their annual catches because the survival of 

 young herrings varies widely from year to year, with a heavy 

 dependence on copepods (Hardy 1965: 62). The fish mature 

 in about 4 years and may live 20 years. 



Information on the age structure of spawning herring 

 was analyzed by Lambert (1987). He noted that it is an 

 underappreciated fact that herring often arrive at spawning 

 grounds in runs or waves. This phenomenon has been reported 

 in both the Atlantic and Pacific Oceans for C.h. harengus 

 and C.h. palasii. It is suggested that spawning proceeds 

 consecutively through year classes from oldest to youngest 

 due to differential maturation. Discrete batches of eggs 

 deposited by these waves of spawning herring give rise to a 

 succession of larval cohorts. The more age classes involved 

 in spawning, the longer will be the spawning season and the 

 spawning will be more widespread since different age groups 

 tend to spawn in different areas. Therefore, it would appear 

 that the maintenance of a wide, well-balanced age structure 

 tends to promote a resilient or more stable population 

 (Lambert 1987). 



Near the Queen Charlotte Islands in British Columbia, 

 shoals of immature herring occur frequently at the surface, 

 where they often jump clear, making a calm sea suddenly 

 erupt in a tiny "boil." Herring boils are often associated with 

 swarms of euphausiids which provide food for the herrings 

 (Gaston 1992: 74). Many seabird species will be found 

 feeding at such prey concentrations. 



In his chapter on the herring. Hardy (1965: 61) wrote: 

 "Early in the year, in March and April, the North Sea herring 

 is feeding very largely on young sand-eels [Ammodytes sp.]; 

 and often at this season you will find the stomach of the 

 herring crammed full of them, lying neatly side by side like 

 sardines in a tin." 



McGurk and Warburton (1992) found that herring and 

 sand lance larvae consumed prey of similar lengths and 

 widths. They concluded that herring and sand lance larvae 

 compete for substantially the same prey resource. More than 

 99 percent of the prey items found in the guts of sand lance 

 larvae were various life history stages of copepods (McGurk 

 and Warburton 1992). 



The work of Carter (1984) and Vermeer (1992) 

 indicated the importance of herring in the diet of murrelets 

 (table 1). Lid (1981) suggested that the breeding failure of 

 Puffins [Atlantic Puffins] (Fratercula arctica) in Norway 

 was due to over-harv esting of herring and, to some extent, 

 over-fishing of sand eels (Ammodytes sp.). Many puffin 

 chicks died, and adult weights were lower during the study 

 period. Spawning stock size in weight*of the Norwegian 

 spring-spawning herring declined fromyapproximately 9.5 



million tons to less than 0.5 million tons between 1950 

 and 1980 (Lid 1981). 



Commercial fishing harvest of herring should be 

 monitored for effects on murrelet reproductive success. In 

 the absence of a sand lance fishery on the west coast of 

 North America, it may be that sand lance populations will 

 respond positively to reduction in herring as documented 

 elsewhere. However, murrelet use of either of these resources 

 will depend on temporal and spatial distribution of the prey 

 relative to murrelet nesting and foraging habitat. The patchy 

 distribution of prey during different seasons must be 

 considered along with changes in offshore distribution of the 

 murrelet between seasons. 



Smelt 



The osmeridae are closely related to salmon and trout, 

 and like trout, have a small, adipose fin. They are confined 

 to arctic and north temperate waters and are best represented 

 in the north Pacific basin. All spawn in fresh water or along 

 the seashore (Hart and McHugh 1944). Among related Pacific 

 species are the surf smelt or silver smelt (Hypomesus 

 pretiosus), capelin. and eulachon or candlefish. 



The silversides (atherinidae) and other unrelated fishes 

 are sometimes also called smelts, sand smelt, or whitebait. 

 The atherinidae also include grunion (Leuresthes tenuis) 

 which occurs north only to the San Francisco area. 



The eulachon has been called candlefish because the 

 flesh is so oily that the dried fish, when provided with a wick 

 of rush-pith or strip from the inner bark of cedar, burns with 

 a steady flame and was used as a candle by the natives. This 

 fish gave rise to the famous "grease trails" which roughly 

 follow the courses of the great northern rivers (Hart and 

 McHugh 1944). The only record of eulachon in murrelet diet 

 was the anecdote by Grmnell (1897) described previously 

 under the section on Alaska. Eulachon are distributed from 

 northern California to the Bering Sea. They seem to feed 

 primarily on euphausiids. Eulachon are important as an 

 intermediate step in the food chain between the euphausiids 

 and larger fish (Hart and McHugh 1944). 



The range of the silver smelt extends from southern 

 Alaska to central California. Some of the smelt may spawn 

 at the end of the first year as has been indicated for Puget 

 Sound fish. They spawn under a great variety of conditions 

 and in most months of the year. Summer spawnings take 

 place both on exposed beaches and at the head of sheltered 

 bays. Usually the fish spawn where there is a certain amount 

 of seepage of fresh water through the fine gravel to which 

 the eggs adhere. Euphausiids seem to be the main food item 

 consumed by silver smelt (Hart and McHugh 1944). 



The capelin is an arctic species with its center of 

 abundance in the Bering Sea or Arctic Ocean (Hart and 

 McHugh 1944). In the Pacific, capelin occur from Alaska to 

 Juan de Fuca Strait. Their distribution in the coastal zone 

 varies seasonally but peaks in June and July when beach 

 spawning occurs. At other times of the year, capelin can be 

 found hi large concentrations in the offshore waters (Jangaard 



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



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