Oyster reef ecosystem services: Finfish utilization and trophic linkages Harris Creek, Maryland, USA

Oyster reefs provide habitat for finfish and their prey. Our project focused on determining the impacts of oyster reef restoration on finfish in the Harris Creek Oyster Sanctuary in the Maryland portion of Chesapeake Bay. As a preliminary step, we examined the utility of using trawls in the place of gillnets to sample finfish but found that trawl samples were also highly variable and that the diets of finfish caught in trawls tended to be different than those caught in gillnets. Based on these findings and the fact that gillnets can be set within reef habitats, all remaining sampling was conducted using gillnets. To assess differences in finfish abundance on oyster reef compared to adjacent non-reef habitats, we used pairs of gillnets to determine catch per unit effort (CPUE). Of the species captured, only white perch showed significantly higher CPUE in reef habitats than in adjacent non-reef habitats. Using only data from on-reef sites, we examined the effect of reef type (restored vs. non-restored) on finfish CPUE. Reef type had no significant effect on CPUE for white perch or striped bass

Integrated assessment of oyster reef ecosystem services: Fish and crustacean utilization and trophic linkages

Using a regression design that encompassed the continuum of oyster reef biomass density in Harris Creek, MD, from unrestored reefs to those restored reefs with the greatest oyster biomass, we examined finfish and crustacean utilization of these habitats. Of the eight sites studied, three had not been subject to any restoration activities and five had been planted in 2012 with juvenile oysters set on oyster shell. All sites were sampled in April, June, August, and October 2015. During each sampling period, we assessed abundance, total length and biomass of finfish and examined gut contents to assess the diets of selected finfish species. Of the species collected that were likely to use reefs as habitat or a foraging ground, only striped bass and white perch were sufficiently abundant to support robust statistical analyses. Regression analyses found no clear relationship between oyster biomass density and catch per unit effort, total length or biomass for striped bass or white perch. Analyses of the effects of sampling period and restoration status (restored versus non-restored sites) on fish utilization frequently found an effect of sampling period but rarely found an effect of restoration status. In all cases where differences were detected, they suggested greater utilization of non-restored sites. Overall, data were sparse and the power of statistical analyses was low. Analyses of striped bass and white perch diets suggest that they are using oyster reefs as a foraging ground. Although comparisons of the proportion of striped bass and white perch that contained prey in their stomachs found no difference between those caught on restored sites versus non-restored sites, gut contents of both species contained prey taxa that are likely more abundant on restored oyster reefs than nonrestored sites. As a percentage of total prey wet weight, polychaete worms were the most important component of striped bass diets in both April (50%) and August (47%). Of the polychaete worms identifiable to species, 100% were Alitta succinea, a species found in much greater abundance and biomass on restored oyster reefs than on comparable non-restored sites (Kellogg et al. 2013, Rodney and Paynter 2006). White perch diets were dominated by the ascidian Molgula manhattensis (52%), a species generally found in greater abundance on hard substrates including oyster reefs. Of the identifiable species of fish found in the stomachs of striped bass, 93% by weight were naked gobies (Gobiosoma bosc) or striped blennies (Chasmodes bosquianus), two species found in greater abundance and biomass on restored oyster reefs than nonrestored sites in Chesapeake Bay (Kellogg et al. 2013, Rodney and Paynter 2006). For white perch, naked gobies accounted for 95% of the identifiable fish species by weight. Direct comparisons of white perch and striped bass diets to the prey fields at each sampling site will be conducted as part of a companion project also funded by NOAA Chesapeake Bay Office (Award #: NA13NMF4570209: Integrated assessment of oyster reef ecosystem services: Macrofaunal utilization, secondary production and nutrient sequestration). This companion project will also provide data on abundance, biomass and distribution of small, reef-associated species including naked gobies, striped blennies, and oyster toadfish (Opsanus tau)