ditions may affect fish larvae in several ways, Bailey 

 and Incze (1985) speculated that sablefish may be 

 particularly sensitive to altered food production. 

 The aim of the present work was to examine the 

 effect of an El Nino event on the food habits of lar- 

 val sablefish, through a comparison of their diet off 

 Oregon and Washington during the 1983 El Nino 

 event and 1980, a year in which oceanographic con- 

 ditions were not anomalous^. Since an earlier study 

 showed that prey size-selection was a function of lar- 

 val size (Grover and 011a 1986), ontogenetic differ- 

 ences in diet were also considered. 



METHODS 



Sablefish larvae were collected by the cooperative 

 U.S.-U.S.S.R. ichthyoplankton survey off Oregon 

 and Washington, during 1980^ and 1983^, using a 

 0.5 m neuston net (Sameoto and Jaroszynski 1969) 

 with 0.505 mm mesh towed for 10 min. Collections 

 were made from 22 April to 4 May 1980 by the RV 

 Tikhookaenskiy and from 22 April to 30 April 1983 

 by the RV Ekvator (Fig. 1). Samples with a mini- 

 mum of 10 specimens were examined. A total of 267 

 larvae collected from 10 stations in 1980 and 136 

 larvae from 6 stations in 1983 were examined. In 

 each year the number of larvae that were examined 

 represented more than 45% of the total number of 

 sablefish that were collected. In conjunction with 

 neuston sampling surface water temperatures were 

 recorded along major transects. 



All larvae were preserved in 10% Formalin^ at 

 sea. Upon sorting they were switched into 5% For- 

 malin, where they remained until their examination. 



After the standard length (SL) of each larva was 

 measured, the digestive tract was removed. Con- 

 tents of the entire digestive tract were evaluated. 

 Only larvae with all or a large portion of the gut in- 

 tact were examined. Gut contents were teased out, 

 and prey items were identified: invertebrate eggs, 

 pteropods, copepod nauplii, copepods, amphipods, 

 euphausid larvae, appendicularians, and other prey 



130° W 



*Sea Surface Thermal Analysis. Dates of issue: 8 May 1980 - 

 6 May 1986. Northwest Ocean Service Center, NOAA, 7600 Sand 

 Point Way N.E., BIN C15700, Seattle, WA 98115. 



^Kendall, A. W., and J. Clark. 1982. Ichthyoplankton off 

 Washington, Oregon and Northern California, April-May 1980. 

 Processed Rep. 82-11, 48 p. Northwest and Alaska Fisheries 

 Center, National Marine Fisheries Service, NOAA, 7600 Sand 

 Point Way N.E., Seattle, WA 98112. 



«Clark, J., and A. W. Kendall. 1985. Ichthyoplankton off 

 Washington, Oregon, and Northern California, April-May 1983. 

 Processed Rep. 85-10, 48 p. Northwest and Alaska Fisheries 

 Center, National Marine Fisheries Service, NOAA, 7600 Sand 

 Point Way N.E., Seattle, WA 98115. 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



FISHERY BULLETIN: VOL. 85, NO. 1 



127° 124° 



-48°N 



Figure 1.— Map of the stations off Washington and Oregon where 

 larval sablefish were collected. Dots represent 1980 collections and 

 crosses represent 1983 collections. 



items. When possible copepods were identified to 

 species. 



Lengths of all prey items were recorded. After 

 the study was begun, it became clear that prey 

 widths should also be measured. From that point on, 

 both lengths and widths were recorded for all prey 

 that were not dorsoventrally or laterally flattened. 

 A conservative approach was taken with prey 

 dimensions, i.e., prey widths excluded appendages 

 and cephalothorax lengths were measured for cope- 

 pods. Both measurements were recorded for a total 

 of 7,508 prey items. 



Diet was analyzed in terms of numerical percent- 

 age composition (%N), percent frequency of occur- 

 rence (%F0), and volumetric percentage composi- 

 tion (%VOL). Prey volumes were calculated from 

 prey dimensions, assuming a spherical shape for 

 invertebrate eggs, while all other prey were more 

 appropriately described by a cylindrical shape. For 

 a comparison, volumes were also calculated assum- 

 ing a spheroidal shape, following Gadomski and 

 Boehlert (1984). Regardless of whether a cylindrical 

 or spheroidal shape was assumed, the relative contri- 



72 



