Reprint Series No. 35

TROPHIC LINKAGES FROM EPIBENTHIC CRUSTACEANS IN LITTORAL FLAT HABITATS: SEASONAL AND REGIONAL COMPARISONS

Charles A. Simenstad, Jeffrey R. Cordell, Kurt L. Fresh, and Mark Carr

1995

Bibliographic Citation
Simenstad, Charles A., Jeffrey R. Cordell, Kurt L. Fresh, and Mark Carr. 1995. Trophic linkages from epibenthic crustaceans in littoral flat habitats: Seasonal and regional comparisons. Washington State Department of Ecology (Publication No. 01-06-029), Padilla Bay National Estuarine Research Reserve Reprint Series No. 35.

Abstract
Investigators at Fisheries Research Institute (FRI), University of Washington (UW) in collaboration with cooperative investigators from the State of Washington's Department of Fisheries, investigated the trophic importance of epibenthic crustaceans in littoral eelgrass (Zostera marina) habitats in the Padilla Bay National Estuarine Research Reserve (PBNERR), two other national estuarine research reserves (South Slough, Oregon, and Elkhorn Slough, California), and a number of other coastal estuaries within this zoogeographic province.

The objectives of this study were to examine spatial and temporal variability in eelgrass epibenthic crustacean prey resources and predation upon them by epibenthic-feeding fishes at PBNERR, and zoogeographic variability among the other two NERR sites and other coastal estuaries. These investigations compared: (1) taxa composition and density of epibenthic crustaceans over a broad distribution of eelgrass habitat in PBNERR; (2) principal epibenthic crustacean prey of epibenthic-feeding fishes over spatial scales in PBNERR; (3) epibenthic crustacean assemblages and their importance as fish prey in eelgrass habitats of other NERR sites and selected coastal estuaries.

Epibenthic crustaceans were sampled from the eelgrass habitat with an epibenthic pump and from eelgrass microhabitats (eelgrass sections) by sampling epiphytes from eelgrass blades. Fish were sampled from adjacent eelgrass habitats by beach seine. Despite the fact that the occurrence of prey organisms consumed by fish (juvenile chum and chinook salmon, shiner perch, Pacific herring, English sole, surf smelt) rearing in the eelgrass habitats shifted among the different locations in one estuary (PBNERR), and across large spatial scales (i.e., zoogeographic) we found that many of the same prey taxa were eaten regardless of the estuary. Spatial variability among the eelgrass habitats within Padilla Bay was reflected in the composition of epibenthic crustaceans. Higher consumption of harpacticoid copepods by fish caught in the interior of the eelgrass habitat (slough sites) corresponded with our results showing higher abundances of prey harpacticoids in these areas, and particularly those associated with eelgrass epiphytes. Our results from zoogeographic pump and eelgrass blade samples were marked by large differences in both species composition and abundances of single taxa across the area studied. A suite of harpacticoid copepods were uniquely associated with eelgrass blade surfaces or epiphytic microhabitats, including the genera Porcellidium, Scutellidilum, Zaus, Harpacticus, Dactylopusia, Diarthrodes, Mesochra, and Heterolaophonte. While many eelgrass-associated harpacticoid taxa occur across the range of locations, often a given site was dominated by one or a few of these taxa, and the dominant taxa often differed among estuaries. Despite this variability, a few selected genera of harpacticoids (Harpacticus uniremis group, Tisbe spp., Zaus spp., Dactylopodia spp.) often comprised dominant portions of the diets of epibenthic-feeding fishes through out the zoogeographic scope of our investigations. Thus, despite inherent spatial variability in epibenthic prey assemblages, predator prey linkages to fishes often appear to be constrained to a few discrete harpacticoid copepod genera. A more thorough understanding of the habitat and microhabitat requirements of these unique "foundation" prey taxa in eelgrass habitats is warranted.