Smith et al.: Distribution and biology of Zaprora silenus 



169 



Figure 1 



Aquarium prowfish specimen, National Marine Fisheries Service, Kodiak Laboratory, 

 Kodiak, AK. Photograph by Jan Haaga. 



behind the tentacles or within the bells of these jellyfish 

 when approached by a remotely operated vehicle, appar- 

 ently as a means of protection from predators. Prowfish are 

 also believed to later become demersal and have a prefer- 

 ence for rocky areas (Tokranov. 1999). 



The association with scyphomedusae and other large ge- 

 latinous zooplankton exhibited by juveniles may continue 

 throughout their lives, because such prey are reported to 

 constitute a considerable portion of the prowfish diet (Car- 

 olio and Rankin, 1998). In the stomachs of 16 juveniles 

 of 5-13.3 cm total length captured at midwater depths in 

 Prince William Sound in 1995, Sturdevant 2 found prey 

 biomass was composed principally of hyperiid amphipods 

 but also found unquantifiable gelatinous matter which was 

 thought to be the remains of jellyfish tentacles. 



Little is known regarding possible predators of prow- 

 fish, the relative frequency of prowfish among prey items, 

 or the sizes of prowfish consumed. Prowfish have been 

 found in the diets of diving seabirds and have comprised 

 25% of food biomass delivered to tufted puffin {Lunda cir- 

 rhata ) chicks (Sturdevant 2 ). Yang ( 1993) found prowfish in 

 only 0.3% of 467 stomachs of Pacific halibut (Hippoglossus 

 stenolepis) taken by bottom trawl in the Gulf of Alaska in 

 1990, accounting for 0.03% (by weight) of total food pres- 



2 Sturdevant, M. V. 1999. Forage fish diet overlap, 1994-1996. 

 Exxon Valdez oil spill restoration project final report (restoration 

 project 97163C), 184 p. Alaska Fish. Sci. Cent., Auke Bay Labo- 

 ratory, Natl. Mar. Fish. Serv., NOAA, Juneau, AK. [Available by 

 order no. PB2000- 100700 from Natl. Tech. Info. Serv, 5285 Port 

 Royal Rd., Springfield, Virginia 22161.] 



ent. Orlov (1998) found prowfish in 0.13% of stomachs of 

 white-blotched skate (Bathyraja metadata) caught by bot- 

 tom trawl off the Northern Kuril Islands and Southeastern 

 Kamchatka in 1996. In comparisons of proximate composi- 

 tion among 17 taxa of forage-size fish from the northeast- 

 ern Pacific (Van Pelt et al, 1997; Payne et al, 1999), juvenile 

 prowfish averaged highest in moisture content (86-88% by 

 weight) and relatively low in lipids (10. 8±1.3%, dry weight 

 analysis). 



In this study we examined information on this little- 

 known species, investigating spatial and depth distribu- 

 tions, size frequency, growth, reproduction, and diet in the 

 waters off Alaska. 



Materials and methods 



Data and sample collection 



Data used in this investigation were collected during 

 bottom trawl surveys for groundfish and invertebrate 

 stocks conducted by the Resource Assessment and Con- 

 servation Engineering (RACE) Division of the Alaska Fish- 

 eries Science Center (APSC), National Marine Fisheries 

 Service. Areas surveyed were the continental shelf and 

 upper slope of the eastern Bering Sea, Aleutian Islands 

 region (Al), Gulf of Alaska (GOA), and west coast of North 

 America from Washington to California. Trawl catches 

 were sorted to species, weighed, and individuals were 

 counted, following procedures described in Wakabayashi 

 etal. (1985). 



