Feeding of Greenland halibut <Emphasis Type="Italic">Reinhardtius hippoglossoides</Emphasis> (Pleuronectidae) in the Kara Sea

Feeding of Greenland halibut Reinhardtius hippoglossoides in the northern Kara Sea was studied based on data collected in summer–autumn 2007–2013. The main food of all size groups of halibut were fish—up to 98% of weight of the food bolus. Larger individuals had lower intensity of feeding as compared to juveniles, which was probably owing to the lack of suitable food for large fish and, along with gonad maturation process, could be one of the reasons of their migration to the Barents Sea. The northern part of the Kara Sea, as well as the adjacent areas of Barents Sea, can be considered as an important area of habitation of juvenile Greenland halibut of the Norwegian–Barents Sea population.     

Biological features of the common fish species in Olyutorsky-Navarin region and the adjacent waters of the Bering Sea: 1. Gadidae (cods) family

Biological features of the three common fish species, pollock Theragra chalcogramma, Pacific cod Gadus macrocephalus, and saffron cod Eleginus gracilis (Gadidae), have been studied using a 20-year dataset (1995?2015). These species inhabit the northwestern Bering Sea in the summer–autumn period and form the schoolings in Olyutorsky-Navarin region. The size–age parameters, as well as the peculiarities of the body length and body weight dynamics, spawning periods, spawning range, and conditions, of the fish caught by different sampling gear have been analyzed. Due to the construction peculiarities and catch efficiency of the different catching gear, the largest specimens are found in the setlines and snurrevads; the fish caught by the trawls are characterized by the smallest size. The body length and body weight of pollock is greater in the pelagic trawl catches compared to the bottom trawl catches. The abundant brood of Gadidae may well be tracked on the multiyear dynamics graphs reflecting the size distribution, as well as by the decrease of biological parameters of the fish. The studied species inhabit the vast growth areas, so smaller body size of them in the coastal waters may be a result of a high ratio of the young specimens there.     

Length–weight relationships for nine Paraschistura species from several river basins of Iran (Teleostei: Nemacheilidae)

Length–weight parameters were estimated for nine nemacheilid fish of the genus Paraschistura from Iran. Significant length–weight relationships with high correlation coefficients were found for all studied species.     

Length‐weight relationships of Secutor interruptus (Valencennes, 1835) and Opisthopterus tardoore (Cuvier, 1829) from the South China Sea,Sarawak

Length–weight relationships for two fish species Secutor interruptus (Valencennes, 1835) (2.3–5.0 cm in size) and Opisthopterus tardoore (Cuvier, 1829) (9.2–15.6 cm in size) were determined. Samplings were conducted at Bintulu coast, South China Sea, Sarawak from September to October 2016 using a pull net having different mesh size from 6 inch at the mouth, 4 inch at the bag area, 2 inch at the panel and 1.5 inch at the cod end. The estimated growth coefficient (b) was 2.96 for S. interruptus and 3.11 for O. tardoore. No information regarding length‐weight relationships was reported previously in FishBase for either S. interruptus or O. tardoore.     

Length–weight relationships for 11 species at three small hydropower plants on the Sapucaí‐Mirim River (Grande River basin,Brazil)

This paper presents length–weight relationships (LWR) for 11 freshwater fish species from the Sapucaí‐Mirim River, a tributary of the Grande River basin, São Paulo, Brazil. The specimens were captured in quarterly samplings between March 2011 and December 2014, using gillnets of mesh size: 1.5–9.0 cm between knots. The present study adds new information for the maximum length of seven species, and presents new LWR records for four species.     

The effects of coastal water pollution of the Black Sea on the blood biomarkers of the round goby <Emphasis Type="Italic">Neogobius melanostomus</Emphasis> Pallas, 1811 (Perciformes: Gobiidae)

The activities of antioxidant enzymes and the contents of the oxidized forms of the proteins in the blood of the Black Sea round goby Neogobius melanostomus, which were sampled in the waters of Sevastopol in 2003 and 2012, were studied. An increase in the values of the tested biomarkers in fish catches of 2012 compared to those of 2003 was recorded. The causes for the observed changes are discussed.     

Length–weight relationships of sixteen freshwater fishes from the Hacha River and its tributaries (Amazon Basin,Caquetá, Colombia)

Body length and weight relationships were estimated for sixteen native freshwater fish species (ten Characidae, three Loricariidae, two Heptapteridae and one Astroblepidae, mainly small‐sized fish) collected in the Andean piedmont Hacha River (Caquetá, Colombia) by electrofishing. These are the first length–weight and length–length parameters reported for the species, which are mostly endemic to the Amazonian basin. Maximum lengths in eight of the sixteen studied species are also reported. Knowledge of this biometric data and their relationships can be relevant in the management and conservation of the local fish and fisheries.     

Length–weight relationships of two Nemacheilid fish species Schistura alepidota (Mirza & Bănărescu, 1970) and Schistura shadiwalensis (Mirza & Nalbant, 1981) from River Swat,Pakistan

In the present study two fish species Schistura alepidota (Mirza & B?n?rescu, 1970) and Schistura shadiwalensis (Mirza & Nalbant, 1981) from River Swat were studied. Fishes were collected using different cast nets (10–12 mm mesh size) in the period of January to August 2017. No information regarding the LWR of these species is available in fish base.     

Peculiarities of the lysozyme content in cods (order Gadiformes) and flatfish (order Pleuronectiformes)

There was analyzed the content of lysozyme-the parameter of the non-specific immunity-in kidney, liver, spleen, and blood serum in 8 fish species of orders Gadiformes and Pleuronectiformes. The cods are characterized by very low level of the enzyme or by the absence of its activity in some organs and in blood serum regardless of the fish habitat. The flatfish demonstrated diversity in the content and distribution of lysozyme in the body of fish of different species. Two flatfish species inhabiting the Okhotsk Sea, with the unique distribution of the enzyme, are revealed. Their peculiarity is due, first, to the highest content of lysozyme in the blood serum among all fish studied earlier; second, to exceeding 2–3 times the enzyme amount in blood serum, as compared to the studied immunocompetent organs. The obtained results confirm the concept that among the fish there exist different related groups differing by the lysozyme activity, and, possibly, by peculiarities of the non-specific immunity as a whole.     

Length–weight and length–length relationships of 139 Indo‐Pacific fish species (Teleostei) from the Davao Gulf,Philippines

Length–weight relationships (LWRs) of 139 coral reef and pelagic fish species (representing 34 fish families) were calculated based on 3806 individuals measured at local fish markets near the Davao Gulf in the southern Philippines during weekly visits between March 2009 and July 2011, as well as in June 2012. Fishes were caught with a variety of fishing methods, corroborated by abrasions and injuries. Forty‐seven of 139 LWRs were firstly reported and new to science. The mean slope b of the LWRs was 3.035, indicating that the majority of studied species followed isometric growth. Standard length – total length relationships were calculated for all measured fish species. Additionally, standard length – fork length relationships are presented for 108 species. Moreover, fifteen new records of maximum fish length and weight are reported.     

Relationships between fish size and otolith size of four bathydemersal fish species from the south eastern Arabian Sea,India

The objective of this study was to estimate a prey body size from the hard parts (e.g. otoliths) of a fish species frequently found in the guts of predators. Length–weight relationships between otolith size (length, height, weight and aspect ratio) and fish size (total length and weight) were determined for four fish species captured in the Arabian Sea by bottom trawl (2015 survey on‐board FORV Sagar Sampada, 200–300 m depth), off the west coast of India: Psenopsis cyanea, Pterygotrigla hemisticta, Bembrops caudimacula and Hoplostethus rubellopterus. No significant differences were noted between the size of the left and right otoliths (t test) in any of the four species. The length–weight relationship of the otolith in all four species showed a negative allometric growth pattern (t test, p < .05). The data fitted well to the regression model for otolith length (OL), otolith height (OH) and otolith weight (OW) to total length (TL) and total weight (TW). Results showed that these relationships are a helpful tool in predicting fish size from the otoliths and in calculating the biomass of these less‐studied fish species during feeding studies and palaentology.     

Effects of feeding on survival, cannibalism, growth and feed conversion of African catfish, Clarias gariepinus (Burchell) in concrete tanks

Daily feeding rates of 0, 2, 4, 6, 8 and 10% of body weight to juvenile (average weight 0.64–65.4 g) catfish, Clarius gariepinus, for 112 days had significant effects on survival, cannibalism, growth and feed conversion ratio (FCR). Survival was significantly higher in fish fed at 6–10% of body weight than those fed at 2–4%. Mortality was mainly caused by cannibalism, being significantly higher in underfed (2–4%) fish than in fish fed at the 6–10% level. A feeding level above 6% did not further reduce cannibalism. The best growth performance was recorded for the fish fed at 8–10% body weight, followed by the fish fed at 4–6%; poorest growth was found for those fed at the 2% level. FCR significantly increased from 2–4% (FCR, 1.14–1.13) to 6, 8 and 10% (FCR, 1.37, 2.18, 2.98, respectively). The results of this study suggest that the optimum feeding rate of juvenile catfish with an average initial weight of about 0.64 g and grown to a size of about 64 g is at 6% body weight per day.     

Length–weight relationships for two loach species,Sinibotia superciliaris (Günther, 1892) and Sinibotia reevesae (Chang, 1944) collected from the Tuojiang River,China

Length–weight relationships were determined for two loach species, Sinibotia superciliaris (Günther, 1892) and Sinibotia reevesae (Chang, 1944). Samples were collected with gill nets (30 × 15 m, mesh‐size 1.5 cm) and fish cages (mesh‐size 0.5 cm) as well as by electroshock (CWB‐2000 P, 12 V, 250 HZ) between May 2013 and June 2015 from the Tuojiang River in southwest China. It is believed that the size range covered is close to a commonly known size range of each species. The length–weight relationship values of b were determined as 3.105 for S. superciliaris and 3.381 for S. reevesae. The data will be helpful in further research regarding these species in the upper Yangtze River Basin.     

Feeding ecology of the tufted puffin (<Emphasis Type="Italic">Lunda cirrhata</Emphasis>) and the horned puffin (<Emphasis Type="Italic">Fratercula corniculata</Emphasis>) in the northern Sea of Okhotsk

The feeding of tufted puffin and horned puffin nestlings was studied on two islands of Tauyskaya Bay of the Sea of Okhotsk: at Talan Island in 1999–2004 and 2006 and Umara Island in 1994 and 1996–1997. The composition of the puffin diet during the breeding season was determined. The main fish species in the diet were determined and the seasonal and annual dynamics of the occurrence of the items was analyzed. Comparative data on biological characteristics, such as the size, weight and age of the fish caught by these birds, as well as the size and composition of food samples, were collected. Differences between the age groups of fish in the diets of the two puffin species were revealed. Conditions for forming of seabird feeding base in Tauyskaya Bay were described.     

Length‐weight relationship of fish species from the Bijagós Archipelago,Guinea‐Bissau

Length–weight relationships were estimated for six teleost fish species occurring in Bijagós Archipelago, Guinea‐Bissau. Samples were collected seasonally during three dry seasons (2013/2014, 2014/2015, 2015/2016) and two rainy seasons (2015 and 2016). Fishes were captured by three methods: angled from the beach or a boat; using beach seine with a mesh size ranging 0.5–1 cm; drift netting from a boat (mesh size 2 cm). This work provides the length‐weight relationship for three fish species that are not reported in FishBase (Citharichthys stampflii, Gerres nigri and Psettodes belcheri) as well as for three species from which we present a wider size range (Eucinostomus melanopterus, Scomberomorus tritor and Sphyraena afra).     

Age,growth and maturity of tub gurnard (Chelidonichthys lucerna Linnaeus 1758; Triglidae) in the inshore coastal waters of Northwest Wales,UK

The tub gurnard Chelidonichthys lucerna has been identified by ICES as a potential commercial species in the northeast Atlantic with recommendations made to monitor landings and discards and to derive information on population biology for stock assessment purposes, however, data are lacking for the species in the northeast Atlantic. Therefore, aims of this study were to provide data on the size/age‐structure and patterns of growth, maturity and mortality of C. lucerna in Northwest Wales, UK, and in doing so to provide data on the biological characteristics of the most northerly population studied to date for comparison with the existing data for southerly Mediterranean populations. Data on the age, growth and maturity of C. lucerna were collected by otter trawling (73 mm cod‐end stretched mesh size) in the coastal waters of Northwest Wales, UK in October (2000–2011, excluding 2006). Total length (TL) of fish sampled ranged between 10.5–41.0 cm (males) and 10.4–57.5 cm (females). The majority of the female fish were between 20–30 cm TL (60.2%) and the majority of the male fish between 20–30 cm TL (58.3%) respectively. TL/weight (W) relations for male and female fish were similar and the combined data was described by W = 0.0067 TL^3.10. Age of fish ranged between 1–7 years old for female fish and 1–5 years old for male fish respectively with the majority of female fish 3 years old (40%) and the majority of male fish 3 years old (37%). The age structures of female and male tub gurnards were not significantly different with the older age classes consisting predominantly of female fish. Both males and females exhibited similar asymptotic growth patterns and the combined von Bertalanffy growth function was TL_t = 51.6 (1 ? e ^{[?0.25(t + 0.41)]}). Instantaneous rates of total mortality were calculated as 1.04 year^?1 for males and 1.11 year^?1 for females. The size (L₅₀) and age at first maturity (A₅₀) were estimated to be 29.1 cm TL and 2.8 years for males, 27.7 cm TL and 2.7 years for females and 28.0 cm TL and 2.8 years for both sexes combined. The results of this study provide the first information on the biology and population dynamics of C. lucerna in the Irish Sea, the first data collected in the northeast Atlantic since 1985 and the most northerly population studied to date.     

The lifecycle of <Emphasis Type="Italic">Dichelyne minutus</Emphasis> (Rudolphi, 1819) (Nematoda: Cucullanidae) in the estuarine biocenosis of the Black Sea

The lifecycle, the host–parasite system, and the ecological features of the nematode Dichelyne minutus (Rudolphi, 1819), which parasitizes invertebrates and fish in the estuarine biocenosis located at the influx of the Chornaya River into the Black Sea (off Sevastopol), have been studied. The host–parasite system of D. minutus includes the polychaete Hediste diversicolor Müller, 1776 (as an obligatory intermediate host) and nine fish species, of which seven are definitive hosts and two are accidental or captive hosts. It has been found that the lifecycle of D. minutus in the biocoenosis of the Black Sea differs from the lifecycle of this nematode that inhabits the Baltic and North seas. In the studied biocoenosis, nematode larvae occur in polychaetes and fish only in the spring and summer; no larvae are found in the autumn (the study was not conducted in the winter). The nematode parasitizes the polychaete H. diversicolor in the spring; the main source of infection in this period is obviously nematode eggs that were laid in the autumn and have overwintered in the environment. The infection process ends by early summer. The seasonal and size–age dynamics of nematode infection of the round goby, Neogobius melanostomus (Pallas, 1814), are analyzed taking the specifics of fish biology into account. The short period of infection, as characterized by the active emission of nematode larvae, their low survival in polychaetes and fish, a short lifecycle and the mortality of mature nematodes after egg-laying in the autumn result in an over-scattered distribution (mostly of the negative-binomial type) of D. minutus in populations of all the hosts.     

Length‐weight relationships for five fishes in the Pengxi River,a main tributary of the Three Gorges Reservoir,China

The length‐weight relationships and new total length are described for five fish species in the Pengxi River basin of the Three Gorges Reservoir. Fish were occasionally sampled from five sites between 2009 and 2014, using various gill nets (mesh size range 2–12 cm) and electrofishing. For four of the five species studied a new maximum total length not yet recorded in previous length‐weight estimates have been found. These data will help to convert length data from field studies in the Three Gorges Reservoir into weight and biomass.     

A radiographic estimation of the effect of temperature on gastric emptying time in Sarotherodon niloticus (L) × S. aureus (Steindachner) hybrids

A radiographic technique was used to determine temperature effects on gastric emptying time in S. niloticus/aureus hybrids. Stomach evacuation times for 30 g fish fed 3% of their body weight were 8.5 h at 30° C, 10.8 h at 25° C and 16.4 h at 20° C. Hence, there was a negative correlation between stomach evacuation time and temperature. The Q ₁₀ between 20 and 30° C was calculated to be 1.92. Similar relationships were found for intestinal evacuation and total evacuation.
The data were used to estimate maximum daily feed intake levels of fish within the size range studied. Levels for 30 g fish were 8.5% body weight at 30° C, 6.6% at 25° C and 4.4% at 20° C. However, the optimum feeding regime should take account of the feeding behaviour of the animals.