In this study, length distribution, length-weight relationship, age, growth parameters, and reproduction of 331 Gobius niger collected monthly by trawling in the Sea of Marmara between October ...2011-July 2014 were determined. The total length and weight distributions of the population varied from 6.2-14.2 cm and 2.85–36.25 g, respectively. The average length was found 10.28 cm and average weight was found 13.71 g. Black goby was distributed between 0-4 age groups. Otolith length-total length relationship was calculated as OL= 2.337*TL+0.143 (R2=0.76). Length-weight relationship were determined total, female, and male as W = 0.096*L3.084 (R²=0.89); females W= 0.010*L3.042 (R2=0.88); males W=0.005*L3.33 (R²=0.94) respectively. The growth parameters were calculated for the whole populations as L∞=15.31 cm K= 0.36 y-1 t0=-1.77 year, L∞=14.89 cm, K=0.35 y-1, t0=-1.97 year for females and L∞=1 4.65 cm, K=0.45 y-1, t0=-1.39 year for males. The natural mortality rate (M) was calculated as 0.82 year-1, total mortality rate (Z) was 1.33 year-1, and fishing mortality rate (F) was 0.51 year-1. The exploitation rate (E) of population was determined as 0.38 year-1. The first sexual maturity length of G. niger was found L50=9.58 cm. The reproduction period was indicated between March to July.
The parasitic copepods Chondracanthus horridus Heller, 1865 and Chondracanthus zei Delaroche, 1811 (Cyclopoida; Chondracanthidae) are recorded for the first time in Turkey. Chondracanthus horridus ...was found on the gill rakers of the black goby, Gobius niger L. and Chondracanthus zei on the gill rakers of the John Dory, Zeus faber L. captured during a trawl survey of demersal fish stock assessment in the Sea of Marmara. The morphological characters of female and dwarf males of copepods were assessed from microphotographs and drawings. This study presents new knowledge about the geographical distribution of these parasites.
The ability to differentiate and localize conspecific calls from the ambient soundscape is particularly challenging for aquatic animals because of the increased wavelength, and concomitant increased ...distortion, of sound underwater. The increased wavelength is especially problematic for fish because of the relatively small space between their two ears, making interaural comparisons difficult. We presented round goby with conspecific calls, two heterospecific calls (
Padogobius bonelli and
Gobius niger), white noise and a 100
Hz tone burst to ascertain the effects of sound structure on localization abilities. The round goby has no obvious hearing specializations, causing theory to predict that it should not be able to localize sounds. In the laboratory, fish were presented with a silent speaker and a speaker playing one sound of interest and their behavioural response was quantified. In all trials except those using
Gobius niger calls, fish preferentially selected the playing speaker over the silent but the intensity of this response differed with sound type. When the round goby call was played, fish came closer to the speaker and swam faster when responding. Also, the ability to directionalize the sound, measured by examining the path taken to the speaker, was significantly better when the conspecific call was played than when other sounds were presented. While it is still unclear how the round goby is able to directionalize the conspecific call, it appears clear they can directionalize, and possibly localize, conspecific calls as well as differentiate between call types.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Male reproductive phenotypic plasticity related to environmental–social conditions is common among teleost fish. In several species, males adopt different mating tactics depending on their size, ...monopolizing mates when larger, while parasitizing dominant male spawns when smaller. Males performing alternative mating tactics are often characterized by a strong dimorphism in both primary and secondary reproductive traits. According to studies on sex-changing species and on species where only one male morph is reproductively active, male alternative phenotypes are expected to vary also in gonadotropin-releasing hormone (GnRH) neurons in forebrain preoptic area (POA). Here, we compared the intra- and inter-sexual variations in number and size of GnRH neurons, along with gonads and male accessory structure investment, in two goby species, the grass goby,
Zosterisessor ophiocephalus, and the black goby,
Gobius niger, characterized by male alternative mating phenotypes. In both species, older and larger males defend nests, court and perform parental care, while younger and smaller ones try to sneak territorial male spawning. We found that grass goby and black goby have different patterns of GnRH expression. Grass goby presents a clear intra-sexual dimorphism in GnRH expression, related to the occurrence of alternative mating tactics, while in the black goby, only inter-sexual differences are observed. The inter- and intra-specific variability in the GnRH neurons in these two goby species is discussed in light of the differences in migratory behavior, nest type, and mating system.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
U radu su prikazani rezultati biometrijske analize – deset morfometrijskih i šest merističkih značajki, glavoča blatara Gobius niger. Ukupno je analizirana 301 jedinka glavoča blatara koji su ...prikupljeni u hrvatskim teritorijalnim vodama. Ukupna dužina tijela svih analiziranih jedinki se kretala u rasponu od 70 mm do 145 mm, sa srednjom vrijednošću od 109.90±15.64 mm. Merističke značajke analiziranih jedinki glavoča blatara iznosile su D1: V-VII, D2: I + 10-14, A: I + 7-12, P: 10-19, C: 14-23, V: 5. Na temelju učestalosti pojavljivanja u analiziranim lovinama uočena su tri područja rasprostranjenja glavoča blatara na području istočnog dijela Jadranskog mora.
