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Decadal Estimates of Pteropods and Larvaceans in the Coastal Gulf Of

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Decadal Estimates of Pteropods and Larvaceans in the Coastal Gulf Of MO D AT SPH N ER A IC IC N A Decadal estimates of pteropods and larvaceans in A D E M I C N O I S L T A R N A O T I I O T A N N the coastal Gulf of Alaska U .S E . C D R E E P M A M RT O MENT OF C Ayla J. Doubleday, & Russell R. Hopcroft Institute of Marine Science, University of Alaska Fairbanks, Fairbanks, AK 99775 Introduction Results Species Composition Limacina helicina Oikopleura spp. Observations along the Gulf of Alaska’s Seward Line 1600 350 1400 Interannual Mean 300 have been taken for nearly 15 years with an Yearly Values 1200 GAK 1 GAK 2 250 ) 1000 GAK 4 GAK 9 emphasis on understanding community level -3 200 800 GAK 12 Spring GAK 13 150 properties of zooplankton. Emphasis has been 600 400 100 placed on the dominant crustacean species, 200 50 0 0 primarily copepods (Coyle and Pinchuk, 2003). In 1998 2000 2002 2004 2006 2008 2010 1998200020022004 200620082010 Clione limacina Limacina helicina Oikopleura spp. Fritillaria spp. recent years, studies have suggested the 700 100 600 80 importance of the lesser abundant larvaceans and 500 60 Figure 4: Larvacean and pteropod groups determined from pteropods to juvenile pink salmon diets (Armstrong 400 Fall 300 40 Mean Abundance Mean Abundance (No m samples collected with 150µm mesh nets. 200 et al., 2005). We attempt to refine the previous 20 100 estimates of their abundance, biomass and 0 0 1998 2000 2002 2004 2006 2008 2010 production, while simultaneously resolving the 1998 2000 2002 2004 2006 2008 2010 species‐level composition missing from that Figure 2: Dark red data represent the mean of all GAK stations sampled with 150 dataset. µm mesh nets (data courtesy of K.O. Coyle). Colored values represent individual Results/Summary stations from our observations using the 53 µm mesh net. • There is large inter‐annual variability in the long‐term dataset for our groups. Our data generally confers longer‐term A. sicula Larvaceans Fritillaria spp. patterns. 400 Oikopleura spp. Spring 2006 400 Spring 2009 O. dioica • Use of 53µm mesh allows us to resolve species for most Methods F. borealis 300 F. pellucida 300 O. labradoriensis specimens. Counts are higher than existing Seward Line data ) -3 200 200 • Species are not equally distributed across the Seward Line; 100 100 to date, five species have been observed. 0 0 • Seasonally, Oikopleura labradoriensis dominates larvaceans 12491213 12491213 400 400 in the spring, while O. dioica dominates in the fall. Fall 2006 Fall 2009 300 300 • Ongoing analysis will expand to the full period of samples Abundance (No m (No Abundance 200 200 collected. In the future, we hope to determine growth rates 100 100 applicable to Gulf of Alaska species, thereby allowing accurate 0 0 estimation of their productivity. 12491213 12491213 Pteropods 3000 C. limacina L. helicina Spring 2006500 Spring 2009 L. helicina LG 2500 400 Figure 1: The Gulf of Alaska Seward Line. 2000 ) 300 -3 1500 Samples have been collected annually in May and 1000 200 References 500 100 August/September since 1998 at 13 stations along 0 0 Armstrong, J.L., Boldt, J.L., Cross, A.D., Moss, J.H., Davis, N.D., Myers, 12491213 12491213 the Seward Line in the Gulf of Alaska. Several sizes 3000 3000 K.W., Walker, R.V., Beauchamp, D.A., Haldorson, L.J., 2005. 2500 2500 of zooplankton nets were used over the top 100 m Fall 2006 Fall 2009 Distribution, size and interannual, seasonal and diet food habits of 2000 2000 of the water column. Here we present an initial m (No Abundance 1500 1500 northern Gulf of Alaska juvenile pink salmon, Oncorhynchus analysis of abundance during 2006 and 2009 using 1000 1000 gorbuscha. Deep‐Sea Research ll. 52:247‐265. the finest‐meshed collections (53 µm). This fine 500 500 0 0 Coyle, K.O., and Pinchuk, A.I., 2003. Annual cycle of zooplankton mesh causes minimum damage to the fragile 12491213 1 2 4 9 12 13 abundance, biomass and production on the northern Gulf of Alaska species, which facilitates species‐level identification. Figure 3: Species abundance of pteropods and larvaceans collected using a 53µm shelf, October 1997 through October 2000. Fisheries Oceanography. Future weights will be predicted from species‐ mesh net at GAK stations 1, 2, 4, 9, 12 and 13. 12: 327‐338. specific relationships to length..
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