Development of mariculture and its impacts in Chinese coastal waters

China has a long history of aquaculture. Since the 1980s, mariculture has been considered by the government as an increasingly important sub-sector of aquaculture. Mariculture provides nutritional and economic benefits, and decreases the intensity of exploitation on declining wild living resources. China now has the highest mariculture production in the world. Kelp made up 50–60% the total Chinese mariculture production in 1967–1980. Production of Laminaria japonicaAresch, the leading species, reached 252, 907 t (dry wet) in 1980. The percentage of kelp production decreased after 1981 because of proportionally greater production of molluscs, shrimps and finfish. Marine finfish and mollusc production increased sharply after 1990. In 2001, the total mariculture production reached 11,315,000 t from a production area of 1,286,000 ha. The rapid development and changes in mariculture species have aroused increasing concern about maricultures impact on the coastal environment. The impact of coastal aquaculture, such as water quality deterioration and contaminants, will have a significant bearing on the expansion of mariculture. The key of improving and maintaining the long-term health of mariculture zones lies in adopting sustainable culture systems. It is imperative that the density of stocking fish and other economically important organisms such as oysters, and scallops, be controlled, in addition to restricting the total number of net-cages in the mariculture zones. The authors suggest moving rafts (cages) periodically and to development of a fallow system in which area fish culture will be suspended for 1–2 years to facilitate recovery of the polluted sediment. Moving fish culture offshore into deeper waters is also suggested. The authors also believe that large-scale seaweed cultivation will reduce eutrophication in coastal culture zones in China.     

Effects of fishing and acidification‐related benthic mortality on the southeast Australian marine ecosystem

Oceanic uptake of anthropogenic carbon dioxide (CO₂) is altering the carbonate chemistry of seawater, with potentially negative consequences for many calcifying marine organisms. At the same time, increasing fisheries exploitation is impacting on marine ecosystems. Here, using increased benthic‐invertebrate mortality as a proxy for effects of ocean acidification, the potential impact of the two stressors of fishing and acidification on the southeast Australian marine ecosystem to year 2050 was explored. The individual and interaction effects of the two stressors on biomass and diversity were examined for the entire ecosystem and for regional assemblages. For 61 functional groups or species, the cumulative effects of moderate ocean acidification and fishing were additive (30%), synergistic (33%), and antagonistic (37%). Strong ocean acidification resulted in additive (22%), synergistic (40%), and antagonistic (38%) effects. The greatest impact was on the demersal food web, with fishing impacting predation and acidification affecting benthic production. Areas that have been subject to intensive fishing were the most susceptible to acidification effect, although fishing also mitigated some of the decline in biodiversity observed with moderate acidification. The model suggested that ocean acidification and long‐term fisheries exploitation could act synergistically with the increasing sensitivity to change from long‐term (decades) fisheries exploitation potentially causing unexpected restructuring of the pelagic and demersal food webs. Major regime shifts occur around year 2040. Greater focus is needed on how differential fisheries exploitation of marine resources may exacerbate or accelerate effects of environmental changes such as ocean acidification.     

Marine reserve recovery rates towards a baseline are slower for reef fish community life histories than biomass

Ecological baselines are disappearing and it is uncertain how marine reserves, here called fisheries closures, simulate pristine communities. We tested the influence of fisheries closure age, size and compliance on recovery of community biomass and life-history metrics towards a baseline. We used census data from 324 coral reefs, including 41 protected areas ranging between 1 and 45 years of age and 0.28 and 1430 km², and 36 sites in a remote baseline, the Chagos Archipelago. Fish community-level life histories changed towards larger and later maturing fauna with increasing closure age, size and compliance. In high compliance closures, community biomass levelled at approximately 20 years and 10 km² but was still only at approximately 30% of the baseline and community growth rates were projected to slowly decline for more than 100 years. In low compliance and young closures, biomass levelled at half the value and time as high compliance closures and life-history metrics were not predicted to reach the baseline. Biomass does not adequately reflect the long-time scales for full recovery of life-history characteristics, with implications for coral reef management.     

Fish and fisheries in hot water: What is happening and how do we adapt?

Rapid climate changes are currently driving substantial reorganizations of marine ecosystems around the world. A key question is how these changes will alter the provision of ecosystem services from the ocean, particularly from fisheries. To answer this question, we need to understand not only the ecological dynamics of marine systems, but also human adaptation and feedbacks between humans and the rest of the natural world. In this review, we outline what we have learned from research primarily in continental shelf ecosystems and fishing communities of North America. Key findings are that marine animals are highly sensitive to warming and are responding quickly to changes in water temperature, and that such changes are often happening faster than similar processes on land. Changes in species distributions and productivity are having substantial impacts on fisheries, including through changing catch compositions and longer distances traveled for fishing trips. Conflicts over access to fisheries have also emerged as species distributions are no longer aligned with regulations or catch allocations. These changes in the coupled natural-human system have reduced the value of ecosystem services from some fisheries and risk doing so even more in the future. Going forward, substantial opportunities for more effective fisheries management and operations, marine conservation, and marine spatial planning are likely possible through greater consideration of climate information over time-scales from years to decades.