Spawning and Feeding Behavior of Captive Pacific Herring, Clupea harengus pallasi

Abstract

Laboratory observations indicate that spawning of Pacific herring (Clupea harengus pallasi) involves very similar if not identical behavior in males and females, and no identifiable behavioral interactions between the sexes. The presence of a sexual pheromone in herring milt is indicated because spawning behavior is rapidly initiated in ripe (ovulated and spermiated) herring of either sex following exposure either to herring milt or to a filtrate of ripe herring testes. Exposure to herring eggs or to filtrates of hake (Merluccius productus) or Pacific cod (Gadus macrocephalus) testes did not elicit such responses. Four components of spawning behavior induced by herring testis filtrate are identified and described: rising and milling, papilla extension, substrate testing, and substrate spawning. Testis filtrates also elicited rising and milling in spent, developing, and mature (unovulated and unspermiated) fish but rising was not followed by papilla extension, substrate testing, or substrate spawning in fish at these earlier stages of gonadal development. Herring at all stages of maturity also displayed rising and milling in response to an olfactory stimulus (filtrate of crushed euphausiids). This feeding response was weakest in the mature and ripe stages, when fish under natural conditions are reported not to feed, and was strongest in the spent stage, when wild fish resume feeding. In terms of the common components of the response to testis and euphausid filtrates (increased swimming speed, rising, and milling), differential responses to these two stimuli were seen only in ripe fish, suggesting herring at other stages of gonadal development may simply perceive milt as a food stimulus.Key words: Clupea harengus pallasi, spawning behavior, pheromone, feeding