De novo reefs: Fish habitat provision by oyster aquaculture varies with farming method

Abstract

Aquaculture industries have the capacity to produce positive ecosystem service benefits, such as the provision of habitat to wild animals. Oyster cultivation is the oldest and largest aquaculture industry in south-eastern Australia. Oyster spat are grown to marketable size in rack-and-rail (‘racks’) or longline-and-basket (‘baskets’) configurations, which add structure to estuarine waters. This study assessed: (1) how the fish communities associated with oyster farms vary with production method; (2) how communities of fish utilise oyster infrastructure, as compared to adjacent natural habitats; and (3) whether oyster infrastructure can serve as de facto oyster reefs by supporting similar fish communities. Remote underwater video surveys, conducted during summer and winter of 2 study years, revealed that fish observations and species richness were generally greater for rack than basket cultivation. Both types of oyster farms supported at least as many species of fish as adjacent natural habitats, including oyster reef, seagrass, mangrove and bare sediment. Fish communities were, in general, most similar between racks and baskets and most dissimilar between racks and bare sediments. Oyster farms supported species of fish otherwise limited to habitats with wild oysters, and unique harvested fish species were observed more frequently at racks. Fish use of oyster-growing infrastructure for foraging and shelter mirrored use of natural biogenic habitats. Overall, this study suggests that the oyster aquaculture infrastructure can support fish communities with species composition similar to those of natural biogenic habitats, although this service is dependent on farming method. Ecosystem services provided by aquaculture should be considered in estuarine habitat enhancement, conservation and restoration.

An ecological assessment of Australia's first community oyster gardens

“…The three-dimensional structure of oyster aquaculture infrastructure is providing comparable foraging, resting and nursery grounds to many natural habitats like remnant oyster reefs, rocky reefs, seagrasses and mangroves (Mercaldo-Allen et al 2019;Mart ınez-Baena et al 2022;Theuerkauf et al 2022). Further studies on oyster gardens initiatives are needed to determine the habitat provided to the larger and more mobile fish species that inhabit these canal estates.…”

“…Indeed, oyster aquaculture infrastructure in Sydney Harbour, Australia, has been demonstrated to support a large abundance of fishes, with a similar community composition to natural biogenic habitats nearby (Martínez‐Baena et al . 2022).…”

Oyster reef restoration - aquaculture interactions: maximizing positive synergies

“…Finally, oyster farms may enhance the probability of establishing healthy reef ecosystems by providing a source of fish and invertebrate colonists, by improving environmental conditions, and by lowering parasite loads. Oyster farms often support many of the same species of fish and macro-invertebrates as oyster reefs, as a result of their habitat structure, and filter-feeding activities (Dumbauld et al, 2009;Martıńez-Baena et al, 2022). Consequently, in locations where remnant oyster reefs are scarce or lacking, oyster farms can play an important role in supplying those populations of fish and macro-invertebrates that characterise reef ecosystems (Martıńez-Baena et al, 2022).…”

“…Oyster farms often support many of the same species of fish and macro-invertebrates as oyster reefs, as a result of their habitat structure, and filter-feeding activities (Dumbauld et al, 2009;Martıńez-Baena et al, 2022). Consequently, in locations where remnant oyster reefs are scarce or lacking, oyster farms can play an important role in supplying those populations of fish and macro-invertebrates that characterise reef ecosystems (Martıńez-Baena et al, 2022). Additionally, filter feeding by cultivated oysters improves water quality (Dumbauld et al, 2009;Humphries et al, 2016) which might facilitate the recruitment of wild oysters.…”

“…Oyster farms are often situated in shallow and sheltered waters, where seagrass meadows naturally occur. Mobile species, such as fish, may move between oyster reefs and other coastal habitats at time scales of tides to years, to shelter and feed (Martıńez-Baena et al, 2022). When poorly managed, oyster farms can have negative impacts on seagrass beds below or adjacent to structures (Everett et al, 1995;Forrest et al, 2009).…”