An increasing number of phylogeographic studies on marine species shows discordant patterns in the degree of population differentiation between nuclear and mitochondrial markers. To understand better ...which factors have the potential to cause these patterns of discordance in marine organisms, a population genetic study was realized on the sand goby Pomatoschistus minutus (Pallas 1770; Gobiidae, Teleostei). Sand gobies from eight European locations were genotyped at eight microsatellite markers. Microsatellites confirmed the global phylogeographical pattern of P. minutus observed with mitochondrial DNA (mtDNA) markers and nuclear allozyme markers. Three groups consistent with the mitochondrial lineages were defined (the Mediterranean, Iberian and North Atlantic groups) and indications of a recent founder event in the northern Baltic Sea were found. Nevertheless, differences in the degree of population differentiation between the nuclear and mitochondrial markers were large (global F(ST)-values for microsatellites=0.0121; for allozymes=0.00831; for mtDNA=0.4293). Selection, sex-biased dispersal, homoplasy and a high effective population size are generally accepted as explanations for this mitonuclear discrepancy in the degree of population differentiation. In this study, selection on mtDNA and microsatellites, male-biased dispersal and homoplasy on microsatellite markers are unlikely to be a main cause for this discrepancy. The most likely reason for the discordant pattern is a recent demographical expansion of the sand goby, resulting in high effective population sizes slowing down the differentiation of nuclear DNA.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The current paper describes three, highly distinctive, new species of Glossogobius from southern New Guinea and northern Australia. The species differ from other species of Glossogobius in the ...combination of small size (maximum size to 50 mm SL), strong sexual dimorphism in mouth and fin sizes and reductions of nape scales and head pores in two of the species. The new taxa are known from small rivers and streams at elevations of less than 100 m.Original Abstract: Description de trois nouvelles especes de Glossogobius de Nouvelle Guinee et du nord de l'Australie. Cet article decrit trois nouvelles especes de Glossogobius du sud de la Papouasie-Nouvelle-Guinee et du nord de l'Australie. Ces especes different des autres especes de Glossogobius par une combinaison de caracteres incluant une petite taille (taille maximale de 50 mm LS ), un fort dimorphisme sexuel de la bouche et de la taille des nageoires, un nombre reduit d'ecailles sur la nuque et des pores de la tete. Elles sont connues de petites rivieres et de ruisseaux a des altitudes inferieures a 100 m.
The goby Parapocryptes serperaster lives on the mud flats in estuaries and has been increasingly exploited as food fish in Mekong Delta, Vietnam,-but little is known on its population, age structure ...and growth. This study aims to understand some basic parameters of its population biology and age used for fishery management and size-selective fishing.- Based on monthly samples over a year, a total of 3002 fish were used for population structure analysis. Fish length distribution and otoliths were used for fish aging. The sex ratio of P. serperaster was near 1:1 and fish size at first entry to fishery was 14.6 cm. The longevity of this goby was 4.05 yr, but fishing mortality (1.57 yr super(-1)) and natural mortality (1.51 yr super(-1)) accounted for 51% and 49% of the total mortality (3.07 yr super(-1)), respectively. Relative yield-per-recruit and biomass-per-recruit analyses revealed the levels of maximum exploitation yield (E sub(max) = 0.83), maximum economic yield (E sub(0.1) = 0.71) and the yield at 50% reduction of exploitation (E sub(0.5) = 0.37). Readable otoliths from female (n=164) and male (n=196) gobies with proper otolith morphometry were used for age identification. The mean age estimated by reading otolith annual rings matched the age estimate from length frequency distribution. The otolith morphometry is a reliable method to age this goby and possibly also applicable for other tropical gobies. The fishery analysis indicates that this goby stock is not overexploited and shows high population recruitment in the Mekong Delta.
The distribution and abundance of habitat specialists is often associated with the availability of preferred habitat; however, other environmental features can also influence habitat selection. ...Coral-dwelling gobies are habitat specialist fishes that depend on the availability of a few key species of coral for their survival and rely on skin toxins to reduce predation risk. This study investigated the influence of benthic substratum around coral colonies on patterns of habitat use and toxicity of two species of coral-dwelling gobies (
Gobiodon erythrospilus
and
Gobiodon histrio
) that compete for access to the coral,
Acropora nasuta
. Field surveys demonstrated that the benthic substratum around
A. nasuta
coral colonies differed between colonies occupied by
G. histrio
and
G. erythrospilus
. Juvenile, single adult and breeding pairs of
G. erythrospilus
mostly inhabited
A. nasuta
colonies surrounded by branching corals. In contrast, juvenile and single adult
G. histrio
associated with
A. nasuta
coral colonies that had adjacent epilithic algal matrix and
G. histrio
breeding pairs inhabited colonies surrounded by sand/rubble. Habitat choice experiments demonstrated that both goby species prefer
A. nasuta
coral colonies with benthic substratum mainly composed by epilithic algal matrix and sand; suggesting that competition for coral colonies in preferred locations could influence patterns of habitat use observed in the field. The substratum around preferred coral colonies also influenced the toxicity levels of associated fishes. Gobies inhabiting
A. nasuta
coral colonies surrounded by epilithic algal matrix and sand showed higher levels of toxicity than gobies collected from colonies surrounded by branching corals. Given the potential for toxicity level to reduce the risk of predation, this could explain why gobies would compete for access to colonies of the preferred coral species surrounded by epilithic algal matrix and sand. These results show that the habitat use of coral habitat specialist fishes can be affected by the benthic composition around preferred coral colonies and demonstrate how competition for important secondary resources can influence patterns of habitat use.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Population dynamics and feeding patterns of invasive
Knipowitschia caucasica
were studied in the littoral zone of the lower Stugna River. The abundances of this goby showed significant inter-annual ...and seasonal fluctuations. The studied population of
K. caucasica
was represented by two age groups (0 and I). Fish die after their first breeding season. In total, 58 prey items were identified in the diet of
K. caucasica
at the sampling site. The most abundant prey were copepods and cladocerans, while the most frequently encountered prey were copepods and chironomid larvae. Copepods were represented mainly by Cyclopoidae. Cladocerans included 21 taxa, among which the most abundant were
Diaphanosoma
sp.,
Acroperus harpae
, and
Disparalona rostrata
; chironomids included 22 taxa, among which the most abundant was
Cricotopus sylvestris
. The diet composition showed seasonal dynamics, where copepods predominated in January to April and in August-September, chironomid larvae were especially important in May to July, while cladocerans were most important in November-December. The relatively high diversity of both phytophilous and open-bottom-dwelling prey organisms in the stomach contents of
K. caucasica
indicates that this species fed on a large variety of benthic habitats including among macrophytes and open areas.
La dynamique des populations et les modes d'alimentation de
Knipowitschia caucasica
, espèce envahissante, ont été étudiés dans la zone littorale du cours inférieur de la Stugna. Les abondances de ce gobie ont montré d'importantes fluctuations interannuelles et saisonnières. La population étudiée de
K. caucasica
était représentée par deux groupes d'âge (0 et I). Les poissons meurent après leur première saison de reproduction. Au total, 58 proies ont été identifiées dans le régime alimentaire de
K. caucasica
sur le site d'échantillonnage. Les proies les plus abondantes étaient les copépodes et les cladocères, tandis que les proies les plus fréquemment rencontrées étaient les copépodes et les larves de chironomes. Les copépodes étaient principalement représentés par des Cyclopoïdes. Les cladocères comptaient 21 taxons, parmi lesquels les plus abondants étaient
Diaphanosoma
sp.,
Acroperus harpae
et
Disparalona rostrata
; les chironomes comptaient 22 taxons, parmi lesquels le plus abondant était
Cricotopus sylvestris
. La composition du régime alimentaire a montré une dynamique saisonnière, où les copépodes prédominaient de janvier à avril et en août-septembre, les larves de chironomes étaient particulièrement importantes de mai à juillet, tandis que les cladocères étaient les plus importants en novembre-décembre. La diversité relativement élevée, dans l'estomac de
K. caucasica,
des organismes proies phytophiles et des organismes proies vivant dans le sédiment indique que cette espèce se nourrissait d'une grande variété d'habitats benthiques, y compris parmi les macrophytes et les zones ouvertes.
The swimming performance of fishes has generally been assessed using a stepped velocity test where the speed at fatigue is considered the critical swimming performance (
U
crit
). Although this test ...was designed for fishes that swim in the water column, it has been applied to fishes that adhere to the substrate. Here we examined the extent to which substrate holding, slipping and swimming contributed to reaching
U
crit
in an example substrate holding fish, the invasive round goby. A linear model indicated that each behavior contributed significantly to
U
crit
, but that substrate holding was by far the biggest contributor (65.8 ± 3.9 % vs. 5.8 ± 0.9 and 28.4 ± 3.4 % slipping and swimming). We also used our behavioural analysis to determine the critical substrate holding speed (
U
hold:
28.6 ± 1.1 cm s
−1
). We conclude that the
U
crit
test can be applied to substrate holding fish but that it is not just an indication of critical swimming speed as is often considered and must be interpreted with caution.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Gobies (Gobiiformes: Gobiidae) are the most species-rich family of fishes in general, and the most abundant fish group in the European seas. Nonetheless, our knowledge on many aspects of their ...biology, including the population genetic diversity, is poor. Although barriers to gene flow are less apparent in the marine environment, the ocean is not a continuous habitat, as has been shown by studies on population genetics of various marine biota. For the first time, European marine goby species which cannot be collected by common fishery techniques were studied. The population genetic structure of two epibenthic species, Gobius geniporus and Gobius cruentatus, from seven localities across their distribution ranges was assessed, using one mitochondrial (cytochrome b) and one nuclear gene (first intron of ribosomal protein gene S7). Our results showed that there is a great diversity of haplotypes of mitochondrial gene cytochrome b in both species at all localities. Global fixation indices (FST) indicated a great differentiation of populations in both studied gobies. Our results did not show a geographic subdivision to individual populations. Instead, the data correspond with the model of migration which allow divergence and recurrent migration from the ancestral population. The estimated migration routes coincide with the main currents in the studied area. This matches well the biology of the studied species, with adults exhibiting only short-distance movements and planktonic larval stages.
The transparent goby (Aphia minuta) is a small progenetic goby that displays a short life cycle with early reproductive maturity and represents a valuable fishery resource harvested by artisanal ...fleets in most part of its distributional range. This study aimed to define the genetic variability in A. minuta at five sampling sites within the Mediterranean Sea and one in the Atlantic Ocean through the analysis of 11 nuclear microsatellite loci. The results revealed that several genetic diversity estimators (expected and observed heterozygosities, mean number of alleles and allelic richness) were lower in the Atlantic Ocean than in the Mediterranean Sea, suggesting the role of past or current demographic events in shaping this pattern. The genetic structure was investigated using both classical genetic differentiation descriptors and Bayesian approaches, and by defining the current and past migration rates. The results obtained revealed a pronounced genetic structure within the Mediterranean Sea and suggest a very low current migration rate. The pattern of historical migration suggests the possible role of hydrographic boundaries in shaping the genetic structure detected in this species. In addition, the identification of loci under selection suggests the possible implication of selective pressures that are acting on genes connected with the peculiar life cycle of this gobiid fish.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
You have reached the maximum number of search results that are displayed.
For better performance, the search offers a maximum of 1,000 results per query (or 50 pages if the option 10/page is selected).
Consider using result filters or changing the sort order to explore your results further.
PDF
