Gobiusculus Research Articles

Food, predation risk and shelter: an experimental study on the distribution of adult two-spotted goby Gobiusculus flavescens (Fabricius)

Adult two-spotted gobies Gobiusculus flavescens (Fabricius) distributed themselves according to the Ideal Free Distribution (IFD) when 10 individuals were offered equal amounts of prey items at two sites in aquaria. As ratios between the prey supply at the two sites increased, however, increasing deviations from the IFD were observed. It is suggested that perceptual constraints within the time scale of the experiments hampered optimal foraging at increased food supply ratios. Introduction of a predator caused a pronounced deviation from the IFD. It is suggested that in the trade-off between food availability and predation risk more emphasis is put on survival than feeding. Introduction of shelter at one of the sites had little or no effect on the observed distribution of gobies when a predator was absent. In the presence of a predator, however, shelter had a pronounced effect on goby distribution. G. flavescens spent up to five times more time in the vicinity of the predator when shelter was present.

Predation Risk Affects Mate Choice in a Gobiid Fish

Predation Risk Affects Mate Choice in a Gobiid Fish

Abundance and spatial overlap of gobies (Gobiidae) in Lough Hyne, Ireland

The densities of gobies (Gobiidae, Pisces) were counted by scuba divers on 13 sublittoral transects in Lough Hyne, southwest Ireland. The characters used for underwater identification are described. Densities ranged up to 6.5 m−2 for Pomatoschistus pictus (Malm), 4.0 m−2 for Gobiusculus flavescens (Fabricius), 0.9 m−2 for Gobius niger L., 0.3 m−2 for G. cruentatus Gmelin, and 0.3 m−2 for Thorogobius ephippiatus (Lowe), while G. paganellus L., G. couchi Miller & El-Tawil and Lesueurigobius friesii Malm were rare on the transects. Gobius cruentatus and T. ephippiatus were largely confined to holes under rocks, while P. pictus and G. niger were most abundant on more open terrain. G. flavescens was hyperbenthic and largely confined to water less than 5 m depth. Significantly less P. pictus, G. flavescens and G. niger were recorded at night, and ‘sleeping’G. flavescens were observed. A working model of the spatial overlap of gobies in Lough Hyne is presented, and the possible roles of diet, predation and temporal activity patterns in interspecific competition are discussed.

Toxicity of rotenone to some potential predators on marine fish larvae — An experimental study

Toxicity of rotenone to some potential predators on marine fish larvae was tested experimentally. Degradation of rotenone in seawater was 0·57% h −1 at 50 lux and 10°C. The content of active rotenone in the commercial solution was, on average, 79% of the expected value, probably caused by age degradation of the product. Fifty per cent mortality of the gobid Gobiusculus flavescens Fabricius occurred after 36, 16 and 5 h in 0·10, 0·25 and 0·50 ppm rotenone solutions, respectively. Fifty per cent mortality of the mysid Praunus flexuosus (O. F. Müller) occurred after 27 h in 5·0 ppm solution. Of the tested species, the carid shrimp Leander squilla L. had the highest tolerance to rotenone, and 10 ppm was necessary to kill all specimens within 48 h. Fifty per cent mortality was registered within 19 h at 10 ppm. The results are primarily compared with studies on limnetic species due to lack of data on marine organisms.

The diet of the two-spot goby, Gobiusculus flavescens (Pisces)

Juvenile and adult two-spot gobies, Gobiusculus flavescens (Fabricius), were collected at three sites in the Plymouth area: the Plymouth Breakwater, Fort Bovisand, and the Yealm estuary. Fish were sampled by a diver-held grab-net, boat-towed zooplankton net, and beam-trawl, from early June until the end of September 1987.Percentage abundance and percentage occurrence dietary data are presented by a graphical technique, such that prey importance (rare or dominant) and fish feeding strategy (specialist or generalist), is visually apparent. It is applied to the different size groups of fish from each site.

A drop-net method for samplinggobiusculus flavescens(fabricius) and other fishes on hard and mixed bottoms with algal cover

Abstract The construction, the sampling procedure and some typical results are described. The device consists of a floating frame (7 × 7 m) with a net suspended on the inside. It is transported by a boat and deployed by means of a pneumatic system and a heavy chain which pulls the net rapidly to the bottom. The net is pursed on the inside of the frame by hand and lifted by a hydraulic winch onboard the boat. The fish fauna caught by the drop-net is compared with the fauna caught in a beach seine, and results on the abundance of Gobiusculus flavescens are presented.

Some notes on small kelp forest fish collected fromSaccorhiza polyschidesbulbs on the Isle of Cumbrae Scotland

Abstract Some preliminary work on the biology of three small fish species, the small-headed cling fish, Apletodon microcephalus; the two-spotted goby, Gobiusculus flavescens; and Montagu's sea snail, Liparis montagui is described. The major component in the diet of all three species was found to be domicolous amphipods. The three species show different activity patterns and different hunting behaviours. Apletodon is a day active searcher, Gobiusculus a day active persuer, whilst Liparis is night active and an ambusher. Some observations of breeding in Apletodon and Gobiusculus have been made. In both the males defend a nest, typically in the bulbous holdfast of the kelp, Saccorhiza polyschides. Nest guarding and tending behaviour in Gobiusculus is energetic whilst in Apletodon it seems to be largely passive. Several females contribute eggs to these nests and a female can lay several batches of eggs through the season. In Apletodon brood size was found to correlate with the size of the male attending it.

A comparative study of the diet of auks killed during an oil incident in the Skagerrak in January 1981

Stomach contents were examined from guillemots Uria aalge (Pont.), Razorbills Alca torda Linnaeus and Little auks Alle alle (Linnaeus) killed by oil in the Skagerrak in January 1981. The range of prey species was small; the commonest fish found in the stomachs were Gobiusculus flavescens (Fabricius), Crystallogobius linearis (Düben), Sprattus sprattus (L.), Trisopterus minutus (L.) and Ammodytes sp. The relative importance of these fish depended on bird species and locality. Guillemots contained gadoids more frequently and sandeels less frequently than razorbills, and the composition of guillemot samples from Oslo Fjord differed from that of samples from Sweden. Invertebrate remains were uncommon in all bird species; the commonest items recorded were polychaete jaws. The frequency of occurrence of items in the diet of guillemots from Oslo Fjord was apparently influenced by the extent of oiling suffered by the birds.

Niche Dynamics and Resource Partitioning in a Fish Guild Inhabiting a Shallow Estuary on the Swedish West Coast

microps (Kroyer), Gasterosteus aculeatus (L.), Pungitius pungitius (L.) and Anguilla anguilla (L.) were the most common species in the guild and P. microps was overall most numerous. The four species Gobius niger (L.), Gobiusculus flavescens (Fabricius), Platichtys flesus (L.) and Pleuronectes platessa (L.) invaded the guild more temporarily. Food resource overlaps were significantly higher in June/July than in September/October. The species decreased their niche widths to increasing diversity in the guild and to a higher species pair overlap values. The diffuse overlap was higher in June/July than September/October. The differences in overlap values, diffuse overlap, decreased number of species together with the reaction of the niche width of each species and the whole guild may explain that competition for food occurred at least temporarily under the study period.

Discussion of methods of investigating the food of fishes, with reference to a preliminary study of the prey of Gobiusculus flavescens (Gobiidae)

The validity, reliability and practicability of different methods for the investigation of stomach contents of a small, plankton-eating fish are discussed. Tests demonstrated the problems related to mass and volume measurements of planktonic food. Several nutrition indices, particularly Hynes's “frequency of occurrence” are criticized. A logarithmic version of Shorigin's index is proposed as a replacement for Ivlev's food selection index. A preliminary study on the food of Gobiusculus flavescens (Fabricius), sampled in July, 1975 at Helgoland, provides some numerical information on the composition of its stomach contents and food preference.