Characterizing the habitat function of bivalve aquaculture using underwater video

Abstract

Bivalve aquaculture is an expanding coastal industry with the potential to modify the habitat of fish and crab species, affecting their refuge, movement, and feeding. The habitat function of shellfish aquaculture is not yet well understood, in part due to difficulties in data collection using traditional methods. Underwater video was used to observe fish and crab species’ affiliations with cultured Pacific oyster Crassostrea gigas and Manila clam Venerupis philippinarum aquaculture sites in comparison to uncultured reference sediment and eelgrass habitats. Sites were monitored in 9 locations across 3 regions of Puget Sound, Washington, USA, in the summers of 2017 and 2018. Of the 3038 fish and crabs observed, 98% were represented by Embiotocidae (surfperch), crabs, three-spined stickleback Gasterosteus aculeatus, Cottidae (sculpins), and Pleuronectiformes (flatfish). Overall, the affiliations of fish and crabs with bivalve aquaculture varied by species groups, culture type, and regional environmental and habitat conditions. These interactions varied on a scale of approximately 150 km, highlighting variation of aquaculture-ecological interactions at a scale not previously recorded in Puget Sound. Species composition varied between aquaculture and non-aquaculture habitats in 2 of the 3 regions studied. Species diversity and richness in aquaculture habitats varied regionally, relative to reference habitats. Pelagic species were more abundant in aquaculture and reference sites that had vertical structure, but abundances of demersal and benthic species on aquaculture habitat relative to reference sites varied regionally. The availability of habitats within intertidal regions, including varying types of aquaculture, could determine community structure for marine organisms such as fish and crab.

Shellfish aquaculture farms as foraging habitat for nearshore fishes and crabs

“…Species that are not associated with structure, such as small flatfish (Williams 1994;Able et al 2005), foraged in unstructured mudflats and oyster flipbag habitat in approximately equal proportions, indicating that oyster flipbags did not impede feeding for several demersal species. Crabs primarily fed in unfarmed mudflats as well as eelgrass-covered substrate; however, very small crabs (e.g., shore crabs) inhabited oyster-on-bottomstyle farm plots in high densities (Ferriss et al 2021) and may have utilized these oyster beds in ways that we were not able to accurately quantify based on video observation.…”

“…The use of cameras to quantify species and behavior is an increasingly common technique that has been employed in similar studies (Gross et al 2018;Muething et al 2020;Ferriss et al 2021;Mercaldo-Allen et al 2021;Shinn et al 2021), and this method allowed us to capture more observations than would have been possible by using dive or snorkel surveys. We used GoPro video cameras to record several hundred hours of underwater video of shellfish aquaculture habitats and adjacent eelgrass and mudflat habitats (Ferriss et al 2021). A subset of these data was analyzed to identify the species present in these habitats and to classify the observed behavior.…”

“…Eelgrass reference sites had high vertical structure and complex benthic surfaces and were composed of a mixture of native eelgrass Zostera marina and invasive Japanese eelgrass Nanozostera japonica. Several cryptic species of demersal fish, such as Bay Pipefish Syngnathus leptorhynchus and gunnels (Pholidae), often co-occur with eelgrass meadows, while some dorsoventrally compressed fish, such as flatfish (Pleuronectidae) and Pacific Staghorn Sculpin Leptocottus armatus (Cottidae), generally are more common in mudflats or clam net habitats (Williams 1994;Able et al 2005;Ferriss et al 2021).…”

Oyster aquaculture cages provide fish habitat similar to natural structure with minimal differences based on farm location

“…Growing anecdotal and scientific evidence suggests that aquaculture gear may provide valuable habitat and ecosystem services for fish (e.g., Ferriss et al, 2021;Mercaldo-Allen et al, 2021;Shinn et al, 2021;Theuerkauf et al, 2021). Off-bottom cages, deployed on the seafloor but elevated several inches off the substrate, are increasingly employed for shellfish aquaculture along the eastern seaboard.…”

“…Small, rugged, waterproof digital or "action" cameras (Struthers et al, 2015) offer a relatively low cost and easy way to collect high quality video that is readily accessible to researchers and citizen scientists alike (e.g., Florisson et al, 2018;Zarco-Perello and Enrıquez, 2019;Ulrich and Bonar, 2020). Recently these video methods have been extended to aquaculture gear and naturally occurring habitat (e.g., Muething et al, 2020;Ferriss et al, 2021;Mercaldo-Allen et al, 2021;Shinn et al, 2021).Video recording of fish interactions with aquaculture gear and natural structure can reveal how fish species at various life history stages use these habitats, produce indices of fish abundance, discern patterns of community composition, identify habitatspecific behaviors and visualize provision of ecosystem services. However, video analysis is extremely labor-intensive, and this recent research has had spatial and/or temporal limitations that constrained the conclusions that could be drawn from the data.…”