Late glacial history of the cold-adapted freshwater fish Cottus gobio,revealed by microsatellites

The distribution of genetic diversity at 10 highly polymorphic microsatellite loci within the European freshwater fish, Cottus gobio, L. was examined. The sampling range comprised a large geographical scale including lineages known to be highly divergent at both mitochondrial DNA (mtDNA) and allozymes. An analysis of genetic variability within populations showed that expected heterozygosity and allelic richness could be explained largely by current effective population sizes. Evidence was found, however, that historical processes predating the last major glaciation affected allelic richness. In addition to confirming the large-scale patterns from earlier studies, the microsatellite data revealed new insights into recent processes by analysing genetic structure within ancient lineages defined by mtDNA data. Stepwise mutation model (SMM) and nonSMM-based methods demonstrated a clear genetic structuring within the Northwestern European lineage comprising populations from Britain and Belgium, and within the Central European lineage populations from the rivers Danube, Elbe and Main. Supported by an analysis of genetic variability within populations these results showed that the bullhead populations most probably persisted throughout the last major glaciation within the British Isles and within the drainages of the rivers Elbe and Main. Such observations provide the first genetic evidence for a glacial refugium in such close proximity to the European glacial margins.     

A new cottid species, Icelus sekii (Perciformes: Cottoidei), from Hokkaido, Japan

A new cottid species, Icelus sekii, is described on the basis of six specimens collected from off Rausu and Urakawa, Hokkaido Island, Japan. This species is distinguished from its congeners by the following combination of characters: supraocular and parietal spines absent; nuchal spine obscure; uppermost preopercular spine unbranched; no scales between dorsal scale row and lateral line scale row, and no scales below lateral line scale row; supraocular, parietal, and nuchal cirri present; five dark brown saddles dorsolaterally; anal fin rays 13; pectoral fin rays 15; vertebrae 12 + 24–25 = 36–37. Icelus sekii can be mature at the smallest size among the species of Icelus. As a secondary sexual character, the male holotype has unique ensiform flaps on the distal tips of the first dorsal fin.     

Porocottus leptosomus sp. nov., from the west coast of Korea, Yellow Sea (Scorpaeniformes: Cottidae)

 A new cottid species, Porocottus leptosomus, is described on the basis of 12 specimens collected from Taean, west coast of Korea, Yellow Sea. The species is distinguished from other species of Porocottus by the following combination of characters: a strongly compressed body, two pairs of branched cirri on the dorsal surface of the head, bases of head cirri smooth, a single cirrus on the dorsal tip of each spine of the first dorsal fin, a single opening of the sixth canaliculus of the infraorbital sensory canal, a long posterior medial canaliculus of the occipital canal with the terminal pore and a few supplementary pores, and melanophores on the isthmus hidden beneath the branchiostegal membrane. Received: January 11, 2001 / Revised: February 7, 2002 / Accepted: March 4, 2002     

Summer distribution of the purplegray sculpin <Emphasis Type="Italic">Gymnocanthus detrisus</Emphasis> (Cottidae) in Waters of Primorsky Krai,Sea of Japan

Results of trawl catches show that in the summer period, in the waters of Primorsky Krai, Russia, Sea of Japan, the purplegray sculpin Gymnocanthus detrisus occurs at depths of 20 to 411 m, preferring the range 80–250 m. The temperature of the species’ habitat varies from 0.8 to 8.6 ° C, and the optimal one is 1.2–2.2 °C. G. detrisus occurs at the preferred depths more frequently in the southern area—the Peter the Great Bay, which is more favorable for foraging; in the area of North Primorsky Krai it was found both at greater and lesser depths. The latter is probably determined by the more limited spreading of waters with unsuitable temperatures for the species there. The body size of the purplegray sculpin grows with depth. Juveniles avoid depths over 200 m, where inflow of low-temperature waters is recorded. G. detrisus, which inhabits waters of Primorsky Krai, is represented mainly by females; the proportion of males exceeds that of females only in the 21–27 cm size group. This may be related to the lower growth rate in males after maturation as compared to females.     

Comparative ecology of prickly sculpin,Cottus asper,and coastrange sculpin,C. aleuticus,in the Eel River,California

Synopsis We documented species' distributions, size structure of populations, abundance in mainstem and tributary streams, habitat use, and diets of prickly sculpin, Cottus asper, and coastrange sculpin, C. aleuticus, in the Eel River drainage of California, to determine the processes allowing coexistence of these very similar fishes. We observed prickly sculpins at 43 sites and coastrange sculpins at 34. The species co-occurred at 26 sites. Young-of-year coastrange sculpins were only observed within 42 km of the ocean, but young-of-year prickly sculpins were present throughout the species range. Mean, maximum, and minimum lengths of coastrange sculpins were positively correlated with distance from the ocean but no significant relationships were found for prickly sculpins. Absolute abundance of both species was highest in mainstem habitat (prickly sculpins = 0.6 sculpins m^–2 and coastrange sculpins = 0.4 sculpins m^–2) . Tributary densities of both species tended to be less than 0.1 sculpins m^–2. The species inhabited very similar habitats and had very similar diets. Coastrange sculpin populations in upstream areas were maintained by immigration from downstream areas in contrast with prickly sculpin populations that produced young-of-year fish throughout their range. Densities were probably not high enough for interspecific interactions to be important. The factors limiting the upstream distribution of the species may include high water temperatures, stability of the stream bed, and behavior of the fish. In the past, the range of sculpins within the Eel River drainage probably fluctuated with changing physical conditions. Recent introductions of exotic species that compete with and prey upon sculpins, and ongoing human activities in the drainage could result in major reductions in the distribution and abundance of one or both species.     

A new species of sculpin,Icelus ecornis (Scorpaeniformes: Cottidae) from the southwestern Okhotsk Sea

A new cottid species,Icelus ecornis, is described on the basis of 31 specimens collected from 159–226 m in the southwestern Okhotsk Sea off Hokkaido, Japan. It is distinguished from all other members of the genusIcelus by the following combination of characters: no supraocular and parietal spines; short blunt nuchal spine; cirri absent from head and body, except for supraocular, parietal and nuchal regions; platelike scales of dorsal row bearing 6–10 long uniform spinules; tubular lateral line scales bearing small spines on dorsal and posterior margins; large oval black spot on first dorsal fin; 16–20 anal fin rays.     

Sound production by the river bullhead, Cottus gobio L. (Cottidae, Teleostei)

Acoustic signals of Cottus gobio consist of knocking sounds produced as single pulses (48 ms) or as trains of 4–6 pulses (230 ms). Frequencies extend up to 3 kHz, but most sound energy is concentrated between 50 and 500 Hz in both sound types. Cottus gobio is solitary, maintains territories, and defends them by threat display, seldom by biting and fighting. Threatening consists of spreading gill covers and fins, darkening, and sound production. Calling is accompanied by a nodding movement of the head, during which the pectoral girdle and the skull are moved rapidly against each other. No difference in ability of sound production was observed between sexes, but males emitted significantly more sounds than females. In the laboratory an increase in vocalization activity was observed between night and day. An increase in the number of encounters and calls was noted when temperatures were raised from 8°C to 13°C. Sound production was registered throughout the year.     

Sound production in the pygmy sculpin Cottus paulus (Cottidae) during courtship and agonistic behaviours

A field study examined sound production in the pygmy sculpin Cottus paulus, a threatened species found only in Coldwater Spring (Coosa River drainage), Alabama where the study was conducted. Two distinct call types are made during both courtship and agonistic encounters: a single knock and a knock train. The duration of the knock train significantly differs between contexts, while the signal structure stays the same. Knock trains are longer when the intended audience is a female, while short and abrupt when intended for a male intruder.     

Relationships of Palearctic and Nearctic 'glacial relict' Myoxocephalus sculpins from mitochondrial DNA data

The relationships among Myoxocephalus quadricornis complex fish from Arctic coastal waters and from 'glacial relict' populations in Nearctic and Palearctic postglacial lakes were assessed using mtDNA sequence data (1978 bp). A principal phylogeographical split separated the North American continental deepwater sculpin (M. q. thompsonii) from a lineage of the Arctic marine and North European landlocked populations of the fourhorn sculpin (M. q. quadricornis). The North American continental invasion took place several glaciation cycles ago in the Early-to-Middle Pleistocene (0.9% sequence divergence); the divergence of the European and Arctic populations was somewhat later (0.5% divergence). The Nearctic-Palearctic freshwater vicariance in Myoxocephalus, however, appears clearly younger than in similarly distributed 'glacial relict' crustacean taxa; the phylogeographical structure is more similar to that in other northern Holarctic freshwater fish complexes.     

Effects of an introduced piscivorous fish on native benthic fishes in a coastal river

1. We used field surveys to compare the density and mesohabitat-scale distribution of the native coastrange sculpin ( Cottus aleuticus ) and the prickly sculpin ( C. asper ) in coastal rivers in north-western California, U.S.A., with and without an introduced piscivorous fish, the Sacramento pikeminnow, Ptychocheilus grandis . We also measured mortality of tethered prickly sculpin in a field experiment including river, habitat type (pools versus riffles) and cover as factors.
2. Average sculpin density ( C. aleuticus and C. asper combined) in two rivers without pikeminnow was 21 times higher than the average density in two rivers in a drainage with introduced pikeminnow. In riffles, differences in the density of sculpins among rivers could be linked to differences in cover. However, riffles in rivers without pikeminnow had an average sculpin density 77 times higher than rivers with pikeminnow, yet only nine times more cover. In pools, cover availability did not differ among rivers, but the density of sculpins in rivers without pikeminnow was 11 times higher than rivers with pikeminnow.
3. In the field experiment, mortality of tethered sculpin varied substantially among treatments and ANOVA indicated a significant River × Habitat × Cover interaction ( P  < 0.001). Overall, tethered prickly sculpin suffered 40% mortality over 24 h in rivers with pikeminnow and 2% mortality in rivers without pikeminnow, suggesting that predation is the mechanism by which the pikeminnow affects sculpins.
4. The apparent reduction in sculpin abundance by introduced pikeminnow has probably significantly altered food webs and nutrient transport processes, and increased the probability of extinction of coastrange and prickly sculpins in the Eel River drainage.