Estimating ecological carrying capacity for stock enhancement in marine ranching ecosystems of Northern China

Abstract

Marine ranching has been proposed as a promising solution to manage the depleted coastal fishery ecosystem in recent decades across China. Marine ranching integrates the practices of artificial habitat-based with aquaculture-based enhancement. Assessing the ecological carrying capacity of target species for enhancement is a precondition for determining the optimal numbers for release, particularly for those species whose habitat restrictions have been eliminated through the construction of artificial habitats in the marine ranch. A responsible approach to stock enhancement aims not only to increase total yield and stock abundance but also to consider any potential effects on ecosystem structure and function. A time-dynamic, ecosystem model was constructed using Ecopath with Ecosim for the Laizhou Bay (Bohai Sea) marine ranching ecosystem in the nearshore waters of northern China. Two sedentary target species with potential for stock enhancement, i.e., the carnivorous red snail Rapana venosa and the detritivorous sea cucumber Apostichopus japonicus, were selected to simulate and estimate their ecological carrying capacities and project their overall effects on the ecosystem. Ecological carrying capacity was defined as the maximum standing stocks of the target species that would not cause “unacceptable” impacts on the ecosystem function and resilience, i.e., not cause any other group’s biomass to fall below 10% of its original biomass. The ecological carrying capacities estimated for R. venosa and A. japonicus were 623.46 and 200.57 t·km−2, respectively, corresponding to 7.8 and 5.0 times higher than their current standing stocks. Simulations of R. venosa enhancement showed distinct effects of increased target species abundance on other functional groups and ecosystem properties. An increase in red snail biomass caused negative impacts on the biomass of most other functional groups and ecosystem indicators, such as Finn’s cycling index, transfer efficiency, and Kempton’s Q index. In contrast, the simulated A. japonicus enhancement had relatively few impacts, and the biomasses of most other functional groups and ecosystem indicators did not change or changed very slightly (<5%). The current model framework provides a means of estimating the ecological carrying capacity in commercial-scale stock enhancement practices and avoiding potential ecological risks for marine ranching in northern China.

The Effect of Marine Pastures on Green Aquaculture in China

“…Therefore, it is easier to realize the scale effect of ecological conservation in the southern marine pasture. From the perspective of the specific operation of marine ranches, the initial cost input and artificial reef input of marine ranches in northern China are unreasonable, and the operation and management bodies are mostly enterprises, which are more likely to produce economic benefits rather than ecological benefits [51]. On the other hand, the model of the proliferation, release, and environmental restoration of marine pastures in the south is more likely to bring ecological benefits and realize intensive management [19].…”

Numerical models reveal the suitable habitat area for the stock enhancement and release of marine organism larvae in Liaodong Bay

“…Previous studies have shown that fluid shear stress caused by waves and tides affects the transport, attachment and recruitment of marine organism larvae (Shanks et al, 2003;Bolle et al, 2009;Reidenbach et al, 2009;Whitman and Reidenbach, 2012;Hou et al, 2022), while water temperature and salinity directly affect larval feeding and development (Zimmerman and Pechenik, 1991;Nurdiani and Zeng, 2007;McGeady et al, 2021). Existing research and the Chinese technical specifications for the stock enhancement indicate the appropriate growth conditions for PTL (China, 2014;Ge, 2019;Wang et al, 2022), as shown in the Table 1 below.…”

“…Many countries have adopted fisheries management measures to address the current decline of marine fisheries resources, including establishing fishing quotas, marine reserves, and stock enhancement (Roberts et al, 2005;Nielsen and Holm, 2007;Colloca et al, 2013;Green et al, 2014). Among them, stock enhancement programs, with their effective ecosystem restoration function and advantage in alleviating the scarcity of fishery resources, are considered to be an important measure for restoring fishery resources (Taylor et al, 2005;Purcell et al, 2012;Han et al, 2016;Wang Z. et al, 2022). Stock enhancement refers to the breeding and release of fish, shrimp, shellfish, algae, and other aquatic organisms into natural waters to allow for their natural growth, in order to increase the population size of marine species, rebuilt biomass of the fished stock, attempting to restore ecological balance (Lorenzen et al, 2010;Hilborn et al, 2020;Pilnick et al, 2021).…”