Shallow Soft Bottoms Research Articles

Abundance, biomass, and seasonal variation of fish on shallow soft bottoms in the Askö area, northern Baltic proper

Abstract The abundance and biomass were estimated using drop-traps. The investigation was carried out from April 1976 to October 1978. Of 185 samples only 8 did not contain fish. Fish of 12 different species and juveniles of one undetermined species were caught. On a yearly basis the mean abundance was 17.64 ind/m2 and the mean biomass was 2.98 g/m2. Four species (the common goby Pomatoschistus microps (Kroyer), the sand goby Pomatoschisius minutus (Pallas), the nine-spined stickleback Pungitius pungitius (L)., and the three-spined stickleback Gasterosteus aculeatus L.) were dominant, constituting over 85% of both abundance and biomass. The two Pomatoschistus species alone constituted over 50 % of both the total abundance and biomass. The common goby was the most abundant species and the sand goby was most important with respect to biomass. There was a strong seasonal variation with the highest values in late summer/autumn (20–30 ind/m2, 2–6 g/m2) and the lowest values in spring/early summer (2–8 ind/m2, ...

Niche separation within the mobile predator guild on marine shallow soft bottoms

Segregation of coexisting predatory fish and shrimp species on marine shallow soft bottoms was studied in the Gullmar Fjord (Sweden). Here, the gobiids Pomatoschistus minutus (Pallas) and P. microps (Krayer) and the brown shrimp Crangon crangon L. are the most abundant epibenthic species close inshore. A temporary reduction in number of one of the species was balanced by an increased recruitment of other species in the guild, so that the overall density of epibenthic predators was kept at approximately the same level. Experimental validation of field results showed that segregation maintained by interspecific territoriality is an important mechanism regulating guild structure. We argue that competitive relations undoubtedly are of importance in maintaining structure of the epibenthic communities in Gullmar Fjord, but of minor importance for overall density of the guild.

Energy budgets and predation impact of dominant epibenthic carnivores on a shallow soft bottom community at the Swedish west coast

The energy flow through the epibenthic community on a shallow soft bottom in Gullmar Fjord, Sweden, is evaluated. The interaction between the dominant epibenthic predators: brown shrimp Crangon crangon L., juvenile plaice Pleuronectes platessa L. and sand goby Pomatoschistus minutus (Pallas), and their food supply is examined, and the fate of the biomass produced within the shallow water ecosystem is described. A steady state model is presented which describes the amounts, pathways and annual rates of energy flowing through the shallow water community. Field and laboratory studies are performed in order to validate the consumption rates of the fish and shrimp species. The brown shrimp occupies a key position in this ecosystem. It represents food, consisting of newly settled juveniles, both to its conspecifics and to other epibenthic species in shallow water. Sixty to eighty per cent of the annual production of shrimps in shallow water is consumed by the epibenthic predators. The brown shrimp constitutes a main predator on other epibenthic species and, by providing such feedback loops, the shrimp constitutes a highly significant regulator of epibenthic carnivores in shallow water. A loss from the benthic community will occur due to predation, maximally amounting to 24–34% of the annual production, which is a high value compared to similar areas. A dynamic simulation is also performed in order to calculate the seasonal change of energy in the epibenthic community in shallow water. Based on mortality calculations, the total output from the shallow nursery should amount to 0·6 g m −2 year −1 (dry wt).

The effect of feeding byYoldia limatulaon bioturbation

Abstract Yoldia limatula is a dominant bivalve in shallow soft bottoms of boreal arctic seas of North America and Europe. This species is a subsurface and surface deposit-feeder. Yoldia's feeding activities result in sediment resuspension through expulsion of loose pseudofaeces directly into the water column. Expelled solids ranging between 10–200 times its body weight daily contain the finer fraction of sediment as pseudofaeces and elongate faeces. Thus feeding results in a fine sediment suspension, a pelletized sediment interface (unstable) and a coarse-grained subsurface. The amount of sediment resuspended was proportional to body size for Yoldia up to 18 mm. Larger animals still expelled greater quantities of sediment per expulsion, however, the frequency of expulsions decreased. The quantity of resuspended sediment was also positively correlated with water temperature above the feeding threshold of 6–8 °C. A 14 mm long Yoldia resuspended approximately 440 g of sediment (dry) each year. Secondary resu...

Seasonal dynamics of small vagile predators on a marine shallow soft bottom

The seasonal on‐ and offshore migrations of the epibenthic community on a marine shallow soft bottom in Gullmar Fjord (Sweden) was recorded for a period of three years. Quantitative sampling was carried out in shallow water (≤ 1 m depth) using drop‐nets. A new sampling device was also introduced which allowed quantitative sampling in deeper water. The brown shrimp Crangon crangon L., juvenile plaice Pleuronectes platessa L. and the gobiid fish species Pomatoschistus minutus (Pallas) and P. microps (Krøyer) constituted the dominant inhabitants of shallow water, contributing >90% of the total number. The annual production was 2.2–2.9 g m−2 yr−1 dry wt with the brown shrimp as the dominant contributor. The abundance in shallow water fluctuated strongly between the seasons, while a relatively small seasonal variation was recorded in deeper water (2.5–10 m depth). The shallow/deep water abundance ratio for the epibenthic community heavily increased during the summer months, for the brown shrimp the ratio exceeded 200 in July. However, the heavy concentration in shallow water did not correspond to the reduced density of animals in deeper water. The boardering deeper water seemed to serve only as a transition area for animals arriving from or migrating to still deeper areas. Heavy mortality in the shallow nursery due to predation by the small epibenthic carnivores may also explain the low abundance in deeper areas during the autumn migration.

Production, Predation and Food Niche Segregation in a Marine Shallow Soft-Bottom Community

A shallow soft bottom in Gullmar Fjord (Sweden) was investigated in order to determine the impact by epibenthic predators and possible competition for food between CO-occurring shrimp and fish species. Large numbers of the shrimp Crangon crangon, juvenile plaice Pleuronectesplatessa and sand goby Pornatoschistus rninutus aggregated during summer in shallow areas and fed on benthic macroand meiofauna. Predation impact was calculated using estimates of gross production efficiencies and productlon rates. In 1976 and 1977, yearly predation amounted to 12 and 17 %, respectively, of the total macroand meiofauna productlon. The low exploitation rate of the benthic community contradicts the hypothesis that predation should be the major extrinsic determinant keeping population levels below the carrying capacity of the environment. Shallow soft bottoms provide an abundant food supply that will neither limit growth nor produce severe competition between the epibenthic predators, although their diets are almost identical. It IS suggested that larger predators will control the abundance of epibenthic feeders such as shrimp, gobies and small flatfish inhabiting shallow water.

Influence of X-Rays on Limb Regeneration in Urodele Amphibians

Influence of X-Rays on Limb Regeneration in Urodele Amphibians