The downstream migration to sea of newly-hatched larvae of amphidromous fishes exposes them to the risk of irreversible starvation if migration takes too long. Some fishes, especially sicydiine ...gobies, exhibit early hatch of eggs, often less than 48 h after fertilisation, and the newly-hatched larvae are at a very early stage of ontogeny, with no functional mouth or fins, no functional eye, and little pigmentation in the eye or elsewhere. This may facilitate survival as it means that downstream migration takes place when plenty of yolk remains, minimising the risk of starvation. Additional behaviours, such as positive phototaxis, continual swimming up into the water column, and hatching during elevated river flows, may also have contributed to rapid downstream transport and survival.
Developing predictive methods to forecast the impacts of existing and emerging invasive species is of critical importance to biodiversity conservation. However, invader impacts are context-dependent, ...making reliable and robust predictions challenging. In particular, it is unclear how temporal variabilities in relation to temperature regime shifts influence invader ecological impacts. In the present study, we quantify the functional responses of three coexisting freshwater fishes: the native freshwater River Goby
Glossogobiuscallidus
, and the non-native Mozambique Tilapia
Oreochromismossambicus
and Western Mosquitofish
Gambusiaaffinis
, under two temperature treatments using chironomid larvae as prey. This was used along with fish abundance data to determine temporal differences in ecological impacts of each fish species between seasons (i.e. at two corresponding temperatures). All three fish species exhibited potentially population-destabilizing Type II functional responses. Their maximum feeding rates were consistently higher in the warm temperature treatment, whereas attack rates tended to be reduced. Non-native Mozambique Tilapia had the highest maximum feeding rate under both temperature treatments (18 °C and 25 °C), followed by the non-native Western Mosquitofish and lastly the native River Goby, suggesting greater
per capita
impacts on native prey by non-native fishes. The predatory fish abundances differed significantly according to season, with native River Goby and non-native Mozambique Tilapia generally more abundant than non-native Western Mosquitofish. By multiplying functional response maximum feeding rates with abundances of each fish species across the seasonal gradient, the relative impact potential of non-native Mozambique Tilapia was consistently higher compared to that of native gobies. Western Mosquitofish impacts were less apparent, owing to their low abundances. We demonstrate how seasonal temperature fluctuations affect the relative impact capacities of introduced species and the utility of consumer functional response and the relative impact potential metric in impact forecasting.
The complete mitochondrial genome sequence of Stonogobiops yasha was first determined in this study. The circle genome was 16,566 bp long and consisted of 13 protein-coding genes, 2 ribosomal RNA ...genes, 22 transfer RNA genes, and 1 control region. The mitochondrial gene arrangement of S. yasha is similar to those of most other gobies. The phylogenetic analysis using the neighbor-joining method showed that the kinship between Stonogobiops and Acentrogobius is closer than those between Stonogobiops and other selected genera. This is the first record of the complete mitogenome for the genus Stonogobiops.
This study presents Ctenogobius boleosoma from the São Luis estuarine region, the first record from the state of Maranhão, northeastern Brazil. This species may have gone unrecorded from Maranhão due ...to the difficulties in collecting gobies by the usual sampling methods, such as gill nets, corking nets, and longlines, even when using nets with an appropriate mesh size.
It is hypothesized that fish larvae undertake vertical movements in estuarine waters. To test this hypothesis, a sampling period was selected during times when many spring‐spawning fish reach maximum ...abundance in coastal waters so that spring and summer variations in larval fish assemblages could be determined in the Yangtze River estuary. Six oceanographic surveys were conducted across the salinity gradient of an inshore (freshwater) and offshore area (brackish intersection) during spring (May) and summer (August) between 2010 and 2012. The fish larval community was dominated by species of Engraulidae, Gobiidae, Champsodontidae and Mugilidae. The pre‐flexion and flexion larval stages of euryhaline marine species, which are dependent on estuaries as nursery areas, were common. The brackish and marine larval assemblage was the most abundant with taxa such as Coilia mystus and Engraulis japonicus accounting for more than 57.3% of the total catch. Spatial differences in the taxonomic composition of larval fish assemblages were evident between the inshore and offshore areas. Additionally, the Yangtze River runoff regulatory functions as affected by the Three Gorges Reservoir operational mode (hydrological alternating operations) showed weak influences on fish and habitat environments. Low salinities from high freshwater inflow limited bay anchovy production in the inshore area.
Fish otoliths from the fossiliferous turbiditic sand deposits outcropping at the Borelli and Moncucco localities (Piedmont, Northern Italy) are herein analyzed. The studied section is Tortonian in ...age and belongs to the lower portion of the Sant’Agata Fossili Formation. The study reveals the presence of at least 90 otolith-based taxa of which 78 are identified at the species level. Two of these are named and described as new species: “Gobiida” bicornuta and “Gobiida” brioche. In addition, 19 taxa, including both still living and extinct ones, are recorded for the first time in Tortonian deposits. Among them, the still living Nansenia aff. oblita, ?Sagamichthys schnakenbecki, and Chaunax pictus are found as fossils for the first time. The high diversity of this well-preserved otolith assemblage improves the systematic knowledge of the Tortonian gobiids and other neritic taxa, which show a close affinity with the present-day Mediterranean fauna. Moreover, the stratigraphic distribution of both neritic and mesopelagic taxa, that were previously considered to enter the Mediterranean Basin in younger stratigraphic intervals, can now be extended back to the Tortonian.
The results of wholesale on the use of waste of vegetable crops and sunflower when fattening gobies of the black-and-white breed are given. Six groups of uncastrated bulls were formed: control, I ...experienced, II experienced, III experienced, IV experienced and V experienced (on the principle of analogous groups, taking into account age and body weight and origin). All gobies (control and experimental groups) were given 17.2 kg of silage from cereal perennial grasses and 3.65 kg of mixed feed and 9.5 kg of brewer's grain, 80g of fodder chalk each. The gobies of the experimental groups were given various wastes of vegetable crops and sunflower (at 30 g / head / day): I experienced - did not feed them, II experienced - pepper stalks, III experimental - sunflower stalks, IV experimental - cucumber stalks, V experimental - stalks tomatoes (in the form of flour). The live weight of bulls when removed from fattening for the control group is 297.0 ± 0.19 kg, the experienced ones - from 304.6 ± 0.12 kg (hay with KKS and without feed additives) to 317.7 ± 0.24 kg (114.7%, tomato stalks). Average daily gains in live weight are from 801 ± 14.6 g (hay with CCR) to 874 ± 16.7 (tomato stalks, P <0.001) versus 762 ± 16.4 g in the gobies of the control group.
Aquatic organisms living in a range of photic environments require specific mechanisms to tune their visual pigments. Maximum absorbance (λmax) of retinal rods in populations of the marine demersal ...sand goby, (Pomatoschistus minutus; Gobiidae, Teleostei) correlates with the local optic environment. It has been shown that this is not regulated through a physiological response by exchanging the rhodopsin chromophore. To test for evolutionary adaptation, the sequence of the rhodopsin (RH1) gene was analysed in 165 Pomatoschistus minutus individuals from seven populations across its distribution range. Analysis showed a high level of intraspecific polymorphism at the RH1 gene, including nonsynonymous mutations on amino acids, known as spectral tuning sites. Population differentiation at these sites was in agreement with the observed differentiation in λmax values. Analyses of dN/dS substitution rate ratios and likelihood ratio tests under site-specific models detected a significant signal of positive Darwinian selection on the RH1 gene. A strong discrepancy in differentiation was noticed between RH1 gene variation and the presumably neutral microsatellites and mitochondrial data. Samples did not cluster according to geographical or historical proximity with regards to RH1, but according to the general photic conditions of the habitat environment of the sand goby. This study highlights the usefulness of sensory genes, like rhodopsin, for studying the characteristics of local adaptation in marine nonmodel organisms.
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