Aspects of the ecology of a littoral chiton,Sypharochiton pellisekpentis (Mollusca: Polyplacophora)

On several Auckland shores, a littoral chiton, Sypharochiton pelliserpentis (Quoy and Gaimard, 1835), was widely distributed and common. At Castor Bay it was the commonest chiton, and its density equalled or exceeded that of the commonest limpet (Cellana spp.) over most of the inter‐tidal range. Spot measurements of population density were made at other sites including exposed and sheltered shores. The smallest animals were restricted to the lower shore in pools or on areas of rock which were slow to drain. Exclusive of these small animals, the population structure was similar in pools and water‐filled crevices situated either high or low on the shore. This was also true for populations of animals from drained surfaces, but, at both shore levels, the population structure in the two micro‐habitats (pools and drained surfaces) was distinct.

Single measurements of salinity in the very small volumes of water in which chitons were living gave a range of 13.3–45.8‰. In laboratory experiments at normal temperatures this species could survive these fluctuations for the maximum time possible between tides. Desiccation experiments, in which weight loss was expressed as a percentage of total water content, showed weight loss to depend on size. No significant differences in weight loss were found between populations from the two shore levels and the two micro‐habitats considered, though there were slight survival differences. Desiccation is probably an important factor influencing population structure, but loss of up to 75% of water content could be tolerated before 50% mortality occurred. Osmotic and desiccation stress evoked a characteristic behaviour pattern.     

Response of phytoplankton to multispecies mariculture:a case study on the carrying capacity of shellfish in the Sanggou Bay in China

A muhispecies model for shellfish polycuhure in the Sanggou Bay in China used for large-scale long-line cultivation of the Chinese scallop Chlamysfarreri, the Pacific oyster Crassostrea gigas and the kelp Laminaria japonica is presented. The model includes key physical processes which are the transports of matter at the system boundary, and the main biological process that is the primary production and nutrients release from the bottom. By the model, the seasonal fluctuations of phytoplankton biomass and dissolved inorganic nitrogen（DIN） in 1994 are simulated. Furthermore, if the kelp culture scale is kept constant and the Chinese scallop and the Pacific oyster culture scales are adjusted, virtual shellfish farms are funded and responses of phytoplankton to the largescale shellfish culture are simulated. According to these simulated results, the room limitation, and the hypothesis that shellfish will not grow well if the phytoplankton biomass is less than 8.2 mg/m^3 , the expandable multiple of scallop culture k and that of oyster culture y are determined as k = -0.276 5y ＋4.690 5 and 0.133 3k ＋0.006 6y≤0.667 5, where, k （ or y） is equal to 1, the culture scale of scallop （ or oyster） is 8.8 x 109 individuals （or 66 ha, with a density of 59 ind./m^2 ）, and the kelp culture scale is 3 300 ha with a density of 12 ind./m^2.     

Prioritising species for research,conservation and management: a case study of exploited fish species

Studies that categorise species according to their conservation status often fall short in their implementation by not having taken into account the impacts on, or the response from, those that either benefit from, or exploit, the resource under consideration. This is especially true in multispecies fisheries where personnel and funding limitations often create the dilemma over which species should be the first to receive management and research attention. This study uses a multicriteria decision analysis approach to prioritise 176 South African linefish species on the basis of a number of criteria indicating conservation and socio-economic, including fishery sector, importance. For each species, conservation criteria were: abundance trend, level of knowledge, vulnerability, range, and relative exploitation throughout that range. Sectoral criteria were: total catch, degree of targeting, the number of participants and the economic value of each species. The scores given to each species on the basis of each of these criteria were summed to allow an examination of each fish's importance from the points of view of (i) conservation, (ii) each fishery sector separately and combined, and (iii) the overall combined conservation and sectoral importance. Different weight sets were used in the weighted summation of the scores, and results were examined for sensitivity. The results were reasonably insensitive to these changes in weights. Relative scores within each of the fishery sectors were dominated by two or three species. Consequently, the scores separating the remaining species from each other were small. This meant that, in many cases, even when the rank of species changed by a number of places with a different weight set, the differences in score were slight. On the whole, the top fish included the most important species in each sector and biogeographical region and in terms of conservation. The separate and overall rankings should assist in the development of broadly acceptable management strategies for different fish species.     

Quantitative trends in sponge ecology research

Abstract It is almost dogmatic that sponges are one of the most relevant groups in benthic marine communities, a statement generally based upon their diversity and abundance in natural communities. But beyond their conspicuousness, do we really know the role that sponges play in nature? Using a series of productivity indicators, this review evaluates the relevance of sponge research to the general scientific community, particularly the contribution of sponge ecology to the broader science of ecology. The relevance of sponge research ranked second out of eight taxonomic groups. Ecology accounted for most of the sponge research output but it ranked poorly compared to the relative importance of the ecological literature in the remaining taxonomic groups. Sponge ecology focused primarily on the species level of organization even though the relevance of these studies fell well below expected. This review suggests that the ecological relevance of sponges is insufficiently supported by ecological data and would benefit from better scientific support. Sponge ecology has the opportunity to contribute to the broader science of ecology in numerous topics where sponge research may be particularly relevant. Broader ecological contributions will help verify the ecological relevance that the great diversity and abundance of sponges suggest.     

Response of phytoplankton to multispecies mariculture: a case study on the carrying capacity of shellfish in the Sanggou Bay in China

A multispecies model for shellfish polyculture in the Sanggou Bay in China used for large-scale long-line cultivation of the Chinese scallop Chlamys farreri, the Pacific oyster Crassostrea gigas and the kelp Laminaria japonica is presented. The model includes key physical processes which are the transports of matter at the system boundary, and the main biological process that is the primary production and nutrients release from the bottom. By the model, the seasonal fluctuations of phytoplankton biomass and dissolved inorganic nitrogen(DIN) in 1994 are simulated. Furthermore, if the kelp culture scale is kept constant and the Chinese scallop and the Pacific oyster culture scales are adjusted, virtual shellfish farms are funded and responses of phytoplankton to the large-scale shellfish culture are simulated. According to these simulated results, the room limitation, and the hypothesis that shellfish will not grow well if the phytoplankton biomass is less than 8.2 mg/m³, the expandable multiple of scallop culture k and that of oyster culture y are determined as k=-0.276 5y+4.690 5 and 0.133 3k+0.006 6y ≤ 0.667 5, where, k (or y) is equal to 1, the culture scale of scallop (or oyster) is 8.8×10⁹ individuals (or 66 ha, with a density of 59 ind./m²), and the kelp culture scale is 3 300 ha with a density of 12 ind./m².     

Dynamic behavior of tension-leg platform with net-cage system subjected to wave forces

In this study a typical tension-leg platform with net cage system is presented, and a set of equations of motion for the platform with a net-cage system of a simplified two-dimensional case are derived. Subsequently a close form solution is obtained when the wave-structure interaction between the top platform structure and the incident wave is considered. The parameter of solidity as a ratio of the twine diameter and the mesh size of the cage is also taken into account in the analysis. The purpose of this study is to investigate the dynamic behavior for the tension-leg platform with a net-cage system and its pre-tensioned tethers when subjected to incident waves and flow drags, and furthermore, to understand the relationship between the structure behavior and the properties of the net-cages. Numerical examples are carried out and the results are discussed focusing on the motion of both the platform and net-cages when subjected to waves of a range of periods. It is found that there is a close relationship between the dynamic behavior of the platform and the net-cage features such as the solidity ratio between the twine diameter and the mesh size of the net-cage while the parameters related to waves are held constant.     

Aspects of larval,post-larval and juvenile ecology of Macrobrachium petersi (Hilgendorf) in the Keiskamma estuary,South Africa

Although Macrobrachium petersi has nine larval stages, only stage I and a minimal number of stage II M. petersi larvae were caught in the Keiskamma estuary. Stage I larvae undergo a vertical migration at night which is markedly influenced by salinity, especially under stratified conditions. Larvae remain in the water column on the ebb tide, a behavioural pattern which effectively carried them to favourable salinities for growth and development. Stage I larvae show an association with salt front regions. The sudden decline in larval abundance from stage I to stage II downstream from the front suggests a change from a pelagic to an epibenthic existence. Later larval stages failed to appear in the plankton. However, post-larvae were caught in the estuary and a juvenile migration from the estuary to freshwater was monitored.     

Development of a skill assessment tool for the Korea operational oceanographic system

A standard skill assessment(SA) tool was developed and implemented to evaluate the performance of operational forecast models in the Korea operational oceanographic system.The SA tool provided a robust way to assess model skill in the system by comparing predictions and observations,and involved the computation of multiple skill metrics including correlation and error skills.User-and system-based acceptance criteria of skill metrics were applied to determine whether predictions were acceptable for the system.To achieve this,the tool produced a time series comparison plot,a skill score table,and an advanced summarized diagram to effectively demonstrate the multiple skill scores.Moreover,the SA was conducted to evaluate both atmospheric and hydrodynamic forecast variables.For the atmospheric variables,acceptable error criteria were preferable to acceptable correlation criteria over short timescales,since the mean square error overwhelmed the observation variance.Conversely,for the hydrodynamic variables,acceptable root mean square percentage error(e.g.,p erms) criteria were preferable to acceptable error(e.g.,erms) criteria owing to the spatially variable tidal intensity around the Korean Peninsula.Furthermore,the SA indicated that predetermined acceptance error criteria were appropriate to satisfy a target central frequency(fc) for which errors fell within the specified limits(i.e.,the fc equals 70%).