The Egg Mortality in Walleye Pollock (Gadus chalcogrammus Pallas, 1814) during Embryogenesis in Waters off the Western Kamchatka Coast

Russian Journal of Marine Biology - Five consecutive ichthyoplankton surveys were conducted during the spawning season of the walleye pollock Gadus chalcogrammus, in April and May 2019, at a...     

Horizontal and Vertical Distribution of the Zebra Mussel (Dreissena polymorpha,Pallas) Larvae in the Modrac Reservoir,Bosnia and Herzegovina

In the Modrac Reservoir, loaded with coal separation suspended material, rapid development of the zebra mussel (Dreissena polymorpha) took place from at least 1987. It is probably the first distinguished “infection” for this part of Balkan Peninsula, caused by this organism. Horizontal and vertical distribution of this mussel, at 15 different reservoir profiles, had been investigated.     

Feeding of Cyclops vicinus (Uljanin) (Copepoda: Cyclopoida) in Lake Balaton on the basis of gut content analyses

Consumption of planktonic algae by Cyclops vicinus living in Lake Balaton were studied in eighteen feeding experiments during 1980–1981. Gut contents of 284 adult C. vicinus were analysed in comparison with the natural phytoplankton assemblage. Rates of algal cells elimination were also studied and compared to controles which did not contain animals. C. vicinus in Lake Balaton was found to be an omnivore.     

Dynamics of feeding and growth of bluegill (Lepomis macrochirus) in Lake Wingra and Lake Mendota,Wisconsin

Adult bluegil grew faster in Lake Mendota than in Lake Wingra. Once and two year old fish from both lakes had similar growth patterns and grew at a rate similar to that of fish from other lakes. Small fish from the two lakes (averaging 10 g) had comparable rations in July but larger fish (averaging 50 g) had daily ration of 3% in Lake Mendota compared to 1% for Lake Wingra fish. Mean number of benthic organisms varied from 364 to 80 per m² in Lake Wingra as opposed to 1560 to 450 organisms per m² in Lake Mendota. Fish in Lake Wingra fed selectively on Daphnia and Cyclops, which, although small in size, were relatively larger than the other plankton species. Bluegill from Lake Mendota, on the other hand, fed mainly on large macroinvertebrates such as Hyalella and insects.     

Feeding ecology of larval and juvenile black seabream (Acanthopagrus schlegeli) and Japanese seaperch (Lateolabrax japonicus) in Tolo Harbour, Hong Kong

Black seabream, Acanthopagrus schlegeli, and Japanese seaperch, Lateolabrax japonicus, are important commercial species in the coastal waters of western Pacific Ocean, including Japan, Korea and China. In Hong Kong, larvae and juveniles of these two species occur in bays and estuaries during late winter and spring. This study reports on the ontogenetic changes in food habits in larvae and juveniles of these species in an artificial rocky shore area. Copepods and cladocerans were the most numerous food items for black seabream. There was a shift to larger and benthic prey as the fishes grew. Japanese seaperch <2.1cm fed predominantly on copepods and cladocerans, while larger prey were added as fish size increased. Japanese seaperch >6.0cm were piscivorous. Maximum prey width increased with fish standard length and mouth gape width in both species. Overall, black seabream showed greater diet breadth than did Japanese seaperch. In black seabream, diet breadth increased with fish size. In Japanese seaperch, diet breadth increased with size for fishes <4.0cm, then decreased as the fishes became piscivorous. Prey selectivity in black seabream was determined using information on prey availability in plankton samples. In general, preference was stronger for cypris larvae, Penilia avirostris and decapod larvae than for copepods and podonids. In recent years, overfishing and environmental degradation have led to the decline of fish populations in Tolo Harbour. Absence of fishes with empty gut indicates that inner Tolo Harbour is still an important nursery area for these two commercial species.     

Feeding ecology of rooks (Corvus frugilegus) on the Heretaunga Plains,Hawke's Bay,New Zealand

Abstract

The food resources of rooks were measured and related to changes in the birds' feeding behaviour during 1968-1970. In all, 381 birds were individually marked with wing tags and colour-coded leg bands and released; their activities were recorded for set periods. Rooks preferred to eat invertebrates and walnuts, but also took seed of cereals, pulses, and stock feeds. They spent at least 40% of their feeding time (75-80% in spring) eating invertebrates, 30-60% finding or hiding walnuts and sometimes acorns in autumn and winter, and 45% eating seed during hot, dry weather in summer. Up to 6% of feeding time was spent eating newly sown or ripening seed. Throughout winter rooks frequently searched for hidden nuts, which they ate or moved to new positions. The proportion of time they spent feeding and the kind of food taken varied seasonally and, in summer and winter, hourly; there were only slight differences between morning, mid-day, and afternoon periods. Rooks spent 65% of the time feeding in autumn, but only 25-30% in spring. Conversely, they spent longer at nest sites from late autumn, peaking at 60% in spring, then less time at nests as they spent longer searching for food. The size of flocks altered with the food being eaten and therefore with season and time of day. Small flocks were widespread where favoured food was plentiful in autumn, winter, and spring, but flocks were larger where food was unevenly abundant in summer and sometimes in winter. During early autumn each bird usually ate and stored walnuts in a selected area of 1-2 km3, returning there later in the season to recover stored nuts. The areas formed only part of the total range used by the study population, and were usually shared with other birds. Tests in aviaries showed that rooks preferred earthworms and walnuts to acorns, maize, and wheat (in that order), and field tests confirmed that rooks preferred walnuts to maize. The numbers of each food item required to sustain a rook for a daylight hour were estimated. Summer is the most difficult season for rooks to find food.     

Density Dynamics and Size Composition of Bivalve Mollusk Larvae of the Genus Mya in Peter the Great Bay (Sea of Japan)

The seasonal population size of planktonic larvae of mollusks of the soft-shell clam genus Mya were studied in Vostok Bay. The larvae occurred in plankton from the first third of June to early September. The highest density of larvae (279.7 ± 98.7 specimens/m³) was found in late June. In early July, larval numbers decreased sharply, and at the end of the first third of July, only single Mya larvae were found in the plankton. Another increase in larval population was observed in early and late August. The larvae varied in length from 175 to 325 m in June–July and from 150 to 250 m in August. It is likely that the larvae of two species of Mya, M. arenaria and M. uzenensis, are present in the plankton of Vostok Bay.     

Effect of growth on reproduction in the freshwater amphipod, Hyalella azteca (Saussure)

A gradient in H. azteca growth was created by reducing food ration. Tests were initiated with neonates (48 h old) and the effects of an altered food ration on survival and growth were examined after 10 and 49 days. Growth rates decreased significantly with reduced food ration (10 day growth rates ranged from 1.2 µg d^–1 in the highest feeding regime to 0.5 µg d^–1 in lowest feeding regime). Survival after 10 days was not affected by ration, ranging from 86 to 96%. A growth rate of 1.2 µg d^–1 at day 10 resulted in mean dry weight (1.0 mg), survival (62%) and reproduction (9.3 neonates/female) at day 49 similar to reported values for this species. Growth rates 0.9 µg d^–1 at day 10 corresponded to significantly reduced reproduction at day 49 (i.e., < 1 neonate per female). Time to the onset of amplexus increased with decreasing ration suggesting reduced ration may have delayed reproduction.     

New data on the historical and expanded range of Proterorhinus marmoratus (Pallas, 1814) (Teleostei: Gobiidae) in eastern Europe

A review of historical and recent area of distribution of tubenose goby Proterorhinus marmoratus was undertaken using critical analysis of published literature, data from two large fish collections (Natural History Museum, Kiev, Ukraine, and Zoological Institute, St Petersburg, Russia), personal collections of the authors sampled during extensive field activities in 1998–2004, and unpublished reports of the Institute of Lake and River Fisheries in Volgograd. Historically, riverine P. marmoratus from the Black Sea–Azov basin were distributed in the upper reaches of the rivers Dnieper and the Don even before the construction of water retention structures; this form at present has demonstrated only limited upstream range expansion. The native ‘Caspian tubenose goby’ is mostly connected with sea and delta habitats. We adduce some arguments for the tubenose goby's recent invasion of the Middle and Upper Volga as a result of introductions of the Don–Azov riverine form rather than upstream dispersal of the Caspian marine form.     

Feeding impact of the planthopper Taosa longula (Hemiptera: Dictyopharidae) on water hyacinth,Eichhornia crassipes (Pontederiaceae)

Taosa longula Remes Lenicov (Hemiptera: Dictyopharidae), a planthopper native to South America, is a candidate for the biological control of water hyacinth, Eichhornia crassipes (Mart.) Solms-Laubach (Pontederiaceae), a serious weed worldwide. Biological control requires agents that are not only specific but also effective. Damage caused by sap-sucking insects is difficult to assess. In this work we designed an experimental and analytical procedure to evaluate the potential damage of T. longula on water hyacinth. The damage that T. longula causes to the clonal reproduction, biomass production, and growth of water hyacinth was studied through a paired greenhouse trial with floating cages. The performance of the plant, starting from two plants per treatment, was evaluated at different insect densities (5, 10, 15 and 20 nymphs per cage) until all the nymphs moulted to adults. The tests showed that individual growth and biomass production of water hyacinth was reduced due to the effect of the insect feeding above five nymphs per cage. The number of new plants produced by clonal reproduction was only significantly different above 15 nymphs per cage. These results suggest that this planthopper could be an effective agent for the biological control of water hyacinth.     

The dynamics of the abundance of the walleye pollock <Emphasis Type="Italic">Theragra chalcogramma</Emphasis> (Pallas, 1814) (gadiformes: gadidae) in the Sea of Japan

The biomass of the walleye pollock (Theragra chalcogramma) stock in waters of Primorskii krai, Sea of Japan, during the 1976–2015 observation period ranged from 48000 to 373000 tons; their number ranged from 99 to 1115 million fish. Four very strong year-classes born in 1975, 1981, 1997, and 2006 have been identified. It has been shown that the duration of the sexual-maturity period is determined by the periodicity of the dynamics of the year-class strength close to the 9-year cycle. According to the results of numerical modeling, an increase in the walleye pollock stock in Primorye is expected from 2017 to 2020.     

Temporal and Spatial Patterns of Epibenthic Macroinvertebrates (EMI) from the San Pedro Shelf,California: Ten-Year Study

Temporal and spatial changes of epibenthic macroinvertebrates (EMI) were described from a ten-year (1985–1995) trawl study on the San Pedro Shelf, California. Community measures including number of species, individuals, biomass, dominance (DI), evenness (J'), and diversity (H' and SR) per trawl were computed for eight trawl stations representing four isobaths. Two reference stations and a test station (located at an ocean outfall) were featured in statistical analyses examining whether the outfall had any effect on EMI. During the ten-year period 127,389 individuals provided 106 EMI taxa. Water depth was the most important factor affecting EMI composition. Although some statistically significant differences in EMI community measures among trawl stations were found. differences between the outfall and both reference stations were either insignificant or inconsistent, providing no obvious ecological impacts attributable to the outfall.     

Size and age composition of populations and growth of Mytilus trossulus (Bivalvia: Mytilidae) in the subtidal area of western Kamchatka

Fairly large Mytilus trossulus beds were found in the subtidal zone at depths to 40 m off the western coast of Kamchatka. The size and age composition of local populations and growth rates of M. trossulus in this region and at Atlasova Island were studied. Significant variability of the shell shape of mollusks was found. In the western Kamchatka subtidal, M. trossulus grew faster than in the northern Kuril Islands and eastern Kamchatka. Mussels attained commercial size (50 mm in shell length) in the fourth year of life in the former case and in the fifth-sixth year in other cases. Mollusks of different ages, from 1 to 8–9 year olds, were present in western Kamchatka populations; i.e., juvenile recruitment takes place regularly, while growth rates vary. Growth and population structure of M. trossulus are discussed in relation to the habitat conditions on the western Kamchatka shelf.     

Feeding ecology of the endangered Valencia toothcarp,Valencia hispanica (Actinopterygii: Valenciidae)

Patterns of food resource utilisation by Valencia toothcarp were studied in a small coastal lagoon in the Iberian Peninsula, its most northern population. Emphasis was placed on feeding activity, diet composition, seasonal and intraspecific variation in diet and feeding strategy. Important features of the overall feeding pattern of the Valencia toothcarp are decreased feeding activity during winter, concentration on benthic invertebrates and narrow dietary breadth, with a focus on gammarid amphipods. The feeding of V. hispanica was independent of seasonal variation in food availability, because its main prey were much the same throughout the year. There were no differences in seasonal niche width and niche overlap between seasons was high. There are also no differences in diets between sexes, although diet composition, niche width and niche overlap differ between juvenile and adult fish. The Valencia toothcarp population from Santes Creus lagoon was formed by specialist individuals, with narrow niche widths, that fed on four preferential prey types, but also consumed some occasional prey.     

Interplay between ecological, behavioural and historical factors in shaping the genetic structure of sympatric walleye populations (Sander vitreus)

Disentangling ecological, behavioural and evolutionary factors responsible for the presence of stable population structure within wild populations has long been challenging to population geneticists. This study primarily aimed at decoding population structure of wild walleye (Sander vitreus) populations of Mistassini Lake (Québec, Canada) in order to define source populations to be used for the study of spatial partitioning using individual-based multilocus assignment methods, and decipher the dynamics of individual dispersal and resulting patterns of spatial resource partitioning and connectivity among populations. A second objective was to elucidate the relationships between biological characteristics (sex, size, age and population of origin) and an individual's probability to migrate and/or disperse. To do so, a total of 780 spawning individuals caught on five distinct spawning sites, and 1165 postspawning individuals, captured over two sampling seasons (2002-2003) were analysed by means of eight microsatellite loci. Four temporally stable walleye populations associated with distinct reproductive grounds were detected. These populations were differentially distributed among lake sectors during their feeding migration and their spatial distribution was stable over the two sampling seasons. Dispersing individuals were identified (n=61); these revealed asymmetrical patterns of dispersal between populations, which was also confirmed by divergent admixture proportions. Regression models underlined population of origin as the only factor explaining differential dispersal of individuals among populations. An analysis of covariance (ancova) indicated that larger individuals tended to migrate from their river of origin further away in the lake relative to smaller fish. In summary, this study underlined the relevance of using individual-based assignment methods for deciphering dynamics of connectivity among wild populations, especially regarding behavioural mechanisms such as differential spatial partitioning and dispersal responsible for the maintenance of genetic population structure.     

On predatory tendencies in the feeding ecology of the fairy shrimp Streptocephalus proboscideus (Frauenfeld, 1873) (Crustacea: Anostraca)

The feeding habits of the filter-feeding fairy shrimp Streptocephalus proboscideus are documented experimentally by offering them ciliates, Volvox, rotifers, nematodes and small crustaceans as prey. Escape capabilities (e.g. swimming speed) rather than size or shape were found to determine these animals' vulnerability to predation by the fairy shrimp. Ingestion rates for Volvox increased hyperbolically with size and, at the high temperatures in which they live, fairy shrimps may daily remove the equivalent of their body weight from the environment.     

Ontogenetic variability in the external morphology of monkey goby, Neogobius fluviatilis (Pallas, 1814) and its relevance to invasion potential

In the previous decade, four species of non-native gobies have invaded the middle section of the river Danube and its tributaries. An effective tool for understanding biological invasions is the evaluation of various biological traits (morphological, life history, ontogenetic) within an epigenetic context. The present study examines the external morphology of monkey goby Neogobius fluviatilis (Pallas, 1814) from the mouth of the River Hron, the morphological differences among three goby species (monkey, bighead and round) and the relevance of these differences for invasive potential. Monkey goby reach their definite phenotype very early in their ontogeny and thus represent a strongly precocial (specialized) species with direct development. The morphological differences between monkey and two other goby species also reflect its strong specialization for sandy substrata and smaller prey types. Thus, monkey goby are not expected to spread to new areas as fast as the round and bighead gobies, and their distribution is likely to be limited to sandy and/or sandy-gravel substrata. If this assumption is correct, then the potential adverse impact of monkey goby on native fauna or even ecosystem is likely to be less than that of the bighead and round gobies. Handling editor: K. Martens     

Feeding on micro-algae in the invasive Ponto-Caspian amphipod Dikerogammarus villosus (Sowinsky, 1894)

Feeding on micro-algae is shown in the invasive Ponto-Caspian amphipod Dikerogammarus villosus. Compared with controls, males, females and juveniles of this species significantly reduced the concentration in suspension of unicellular micro-algae. Juveniles had higher concentrations of algae in the cardiac gut than adults. The presence of these algae in the mid- and hindgut was also recorded. This feeding behaviour was filmed and the mechanisms involved are described and discussed. We comment on the use of the Functional Feeding Group (FFG) concept to classify feeding in amphipods. The role of being a feeding-generalist in aiding the invasion process is also discussed.An erratum to this article can be found at     

Role of Corpus Allatum on the Modulation of Feeding Rhythm in the Semilooper Caterpillar,Achaea Janata (L)

A circadian feeding rhythm which may be entrained by photoperiod was found in fifth instarcaterpillars of the lepidopteran, Achaea Janata (L.). AUatectomy reduced the amount of food consumed; this consumption was significantly lower during the fifth instar in both allatectomized and sham-operated insects. An apparent circadian feeding pattern appeared on day 2 in the sham-operated caterpillars. Topical application of the anti-allatin, Precocene-II (50μg/animal) also reduced leaf consumption significantly compared to the respective controls, although these controls maintained the same apparent circadian feeding rhythm on day 2.