70 



Fishery Bulletin 92(1). 1994 



Table 1 



(A) Composition of microzooplankton in Shelikof 

 Strait during spring, expressed as a percent of 

 total organisms counted. Hyphens indicate values 

 greater than zero but less than 2%; non-zero val- 

 ues shown are rounded to nearest whole number. 

 Shed ovisacs are from Oithona spp.; "Other" in- 

 cludes infrequent and unidentified organisms. (B) 

 Vertically integrated abundances of organisms are 

 averaged across Shelikof Strait for each year; "All 

 other" refers here to all categories from (A) com- 

 bined except for those specifically listed. 



A Percent composition 



( 'ategory 



1985 1986 1987 1988 1989 



Copepod nauplii 



Other nauplii 



Invertebrate eggs 



Ovisacs 



Copepods 



Euphausiids 



Rotifers 



Tinitinnids 



Larvaceans 



Polychaetes 



Echinoderms 



Foraminifera 



Other 



50 



46 54 82 76 



25 

 3 

 9 



35 



2 

 



7 



L3 



14 



11 







B Average integrated abundance (1000s m -2 ) 

 from 0-60 m 



Copepod nauplii 

 Invertebrate 



eggs 

 All other 

 Total 



5.8 13.9 17.6 9.4 9.6 



3.0 10.4 



4.6 5.7 



13.3 30.0 



3.6 0.4 0.6 



8.6 1.9 2.6 



29.8 11.8 12.8 



set at 25 units in both the X and Y directions. The 

 same technique was used for contouring CTD and 

 nutrient data. A subset of contours from all three 

 data types was compared by inspection to the origi- 

 nal input data to look for artifacts caused by the 

 contouring software. Integrated abundances of nau- 

 plii across the Strait were compared for the four 

 years which had late April-early May sampling 

 (1985, '86, '88, '89). Data were taken from those sta- 

 tions (#55, 58, 61) sampled every year in the series 

 and were compared by using a non-parametric two- 

 way analysis of variance (ANOVA) on ranks (also 

 referred to as the Quade test: Conover, 1971). A 

 multiple comparison based on ranks (Conover, 1971) 

 was applied when the ANOVA showed statistically 

 significant differences. 



We used the estimated abundances of adult fe- 

 male copepods (No. m" 2 ) from the oblique bongo tows 



to consider possible sources of planktonic eggs and 

 nauplii sampled in our study. Data are from a da- 

 tabase being used to describe spatial and 

 interannual patterns of major zooplankton taxa 

 (FOCI Database, National Marine Fisheries Service, 

 Seattle); subsampling and counting followed stan- 

 dard procedures and are detailed in a series of five 

 reports (e.g., Siefert and Incze, 1991 4 ). The relative 

 contribution of each taxon to the standing stock of 

 planktonic copepod eggs and early nauplii was esti- 

 mated by using egg production rates reported in the 

 literature or from unpublished data. This is simplis- 

 tic, because it ignores changes in egg and naupliar 

 concentrations as a function of birth rate, develop- 

 ment time, and mortality, all of which may vary 

 considerably. However, the calculations provide a 

 rough evaluation of potential sources of nauplii in 

 Shelikof Strait. Sizes of eggs and early nauplii (e.g., 

 Nauplius I [NI]) were used when reports were found. 

 We used the following information: Calanus 

 marshallae (eggs 175-185 |im, fecundity 12 eggs 

 d : [Runge, 1990 5 1; Calanus pacificus (eggs ca. 160 

 urn, fecundity 38 eggs d" 1 [Runge, 19841; NI ca. 220 

 Urn CL [Fulton 19721); Metridia pacifica (eggs 150 

 urn [Runge, 1990 6 1; fecundity 2.5 eggs d" 1 

 [Batchelder and Miller, 1989)); Pseudocalanus spp. 

 (eggs ca. 110-130 urn retained in ovisacs [Frost, 

 1987]; fecundity 4 eggs d" 1 [Dagg et al., 1984; Paul 

 et al., 1990]; NI ca. 180 pirn CL [Fulton, 1972]). 

 Jeffry Napp 7 and Kenric Osgood 8 both have found 

 that Metridia pacifica held in the laboratory may 

 produce eggs at higher rates, and they suggest that 

 the population average at times may be several 

 times greater than the rate given above. 



Results 



In this section we designate different transects by the 

 year in which they were sampled but do not mean to 

 imply that the differences necessarily were interannual. 

 We address this distinction in the discussion section. 



Nitrate concentrations in bottom waters were 

 highest in 1985, 1988, and 1989 (>25 ug-at L" 1 com- 



4 Siefert, D. L. W., and L. S. Incze. 1991. Zooplankton of Shelikof 

 Strait, Alaska, April and May 1989: data from Fisheries Ocean- 

 ography Coordinated Investigations (FOCI) cruises. Alaska 

 Fish. Sci. Center, NOAA, Seattle, WA, 119 p. 



5 J. Runge. 1990. Insti. Maurice Lamontagne, Mont-Joli, Que- 

 bec, Canada, pers. commun. 1990. 



6 J. Runge. 1993. Inst. Maurice Lamontagne, Mont-Joli, Quebec, 

 Canada, unpubl. data. 



7 Jeffry Napp. Nat. Mar. Fish. Serv., Alaska Fishereis Science 

 Center, Seattle, WA, pers. commun. 1993. 



8 Kenric Osgood, Dep. Oceanography, Univ. Washington, Seattle, 

 WA, pers. commun. 1993. 



