bluuebunny/crossref_metadata_2025_split huggingface dataset:
Predation on adult Atlantic salmon, Salmo salar L., by otters, Lutra lutra (L.), within the River Dee system, Aberdeenshire, Scotland
Authors: Carss D. N. , Kruuk H. , Conroy J. W. H. 
Published: January 2006

Predation on adult salmon, Salmo salur L., by otters, Lurra lutra (L.), varied seasonally on the R. Dee, Aberdeenshire, Scotland, being highest during the spawning season in winter. Predation is described for some tributaries of the river. Male fish were caught by otters more often than females, and it is suggested that they were most vulnerable during their extensive excursions up and down stream, particularly as they negotiated shallow riffles. Otters appeared to prey upon healthy fish rather than those infested with Saprolegnia sp. but there was no difference in the size, freshwater‐ or sea‐age offish killed by otterscompared with ‘kelts’ which had died non‐violently. At least some of the otters obtained most of their daily food requirements by catching a single salmon per night.Considerable numbers of adult salmon may be killed by otters during the spawning period but it is suggested that, because most are males, this is unlikely to affect the breeding success of the salmon population. Most predation occurs outside the fishing season and so is unlikely to reduce the numbers of salmon caught by anglers.
Tidal movements of shallow water fishes in Kuwait Bay
Authors: Wright J. M. , Clayton D. A. , Bishop J. M. 
Published: January 2006

The intertidal migrations of shallow water fishes in Kuwait Bay were studied during two 24 h periods using an otter trawl. Most species wereconcentrated at a location corresponding to Low Low Water mark. At the other tidal levels some fishes migrated with the tide to High High Water mark through a horizontal distance of up to 2 km. Any effect of day and night on the catch was masked by the effect of tidal condition. Leiognarhus decorus (de Vis) was typically concentrated at Low Water but a proportion of the population followed the rising tide toward the shore. There was a die1 effect whichmay have been due to fish moving to shallower water at night compared with the day. Length‐frequency distribution changed slightly with tidal state so that larger fish were not captured at High Water during the day. Of the fishes captured at high tide, the largest individuals of L. decorus were captured at a depth of 2.0 m deep. Solea elongata Day did not migrate with tidal fluctuations and was captured in large numbers only at Low Water. Arius tenuispinis Day was captured in shoals at or around Low Water.
Colonization, larval survival and epidemiology of the nematode Anguillicola crassus, parasitic in the eel, Anguilla anguilla, in Britain
Authors: Kennedy C. R. , Fitch D. J. 
Published: January 2006

In late 1987, immature Anguillicola crassus were reported for the first time in Britain from eels from two river systems. By late 1988, gravid adults were present in a number of rivers in the east of England in two discrete centres of distribution: one in East Anglia correlated with the route taken by lorries exporting eels to the continent, and one in the R. Thames correlated with the import of eels to London. The parasite was firmly established in the R. Trent, where prevalence levels reached 100% in some places.Laboratory investigations showed that adult parasites and their eggs remained viable even after infected eels had been maintained for 4 weeks in 100% sea water. Hatching of eggs declined with increasing salinity, but was not totally inhibited by sea water. Survival and infectivity of freeliving second stage larvae were maximal in natural fresh water (95% survival for 4 months, and 50% still infective to copepod intermediate hosts after 70 days), but declined in alkaline water and with increased salinity. Nevertheless, in 100% sea water, 50% of larvae were still infective after 8 days. Specificity to the intermediate host was low, and eels of all sizes could be infected.These characteristics, plus a high reproductive potential, give the parasite exceptional colonization potential and ability, enabling it to survive natural movements of eels from catchment to catchment and to increase rapidly within a new locality. The ability of free‐living larvae to adhere to the substratum and survive in sea water enables them to survive in eel‐transport lorries from which they will not readily be removed by flushing, the normal cleansing procedure. It is concluded that there were two separate introductions of the parasite to Britain; via the eel import trade through London, and, totally unexpectedly, via the eel export trade in lorries traversing East Anglia. The parasite is now firmly established in Britain and will continue to spread by natural movements of eels but especially by human‐assisted movements of infected eels for stocking and market. This latter practice is recognized as a major factor in introducing and disseminating fish parasites.
Seasonal changes in energy and the energy cost of spawning in Gulf of Alaska Pacific cod
Authors: Smith R. L. , Paul A. J. , Paul J. M. 
Published: January 2006

In the Gulf of Alaska, adult Pacific cod exhibited an annual cycle of condition, gonad index and liver index in which maximum values occurred in ripe fish in March and minima in July. About 30–31 % of prespawning stored energy was expended during the spawning effort. The energy associated with spawning derived from liver (24% and 18%), somatic tissue (22% and 33%) and gonad (53% and 48%) for females and males, respectively. Liver index and gonad index at the time of sampling were directly related in females, but in males gonad index was best related to liver index 1–3 months earlier.The Pacific cod is very similar to the Atlantic cod in terms of energy cycling, maximum gonad sizes, energy expended during spawning and gonadal contribution to energy expenditure. However, in Pacific cod, somatic tissue contributes markedly to energy expended during reproduction. The Pacific cod cod differs from the walleye pollock with respect to gonad index (13% and 20%ν. 20% and 8% for females and males, respectively), spawning weight loss (25%ν. 38%), liver energy loss during spawning (71%ν. 55%) and energy cost of spawning.
Diet and prey selection of six species of tuna baitfish in three coral reef lagoons in the Solomon Islands
Authors: Milton D. A. , Blaber S. J. M. , Rawlinson N. J. F. 
Published: January 2006

The diets and prey selection of six species of tuna baitfish (the engraulids Stolephorus devisi and S. heterolobus, three dussumierids of genus Spratelloides, and the apogonid Archamiazosterophora. were examined at two heavily fished and one unfished site in the Solomon Islands. All species ate almost exclusively nektonic zooplankton, especially crustaceans. Calanoid copepods were the most importantpreyofallspeciesexcept A. zosterophora, whichateagreater biomassoflarvalfish. Baitfishcould be divided into two groups according to prey taxa: the apogonid A. zosterophora and the engraulids S. devisi and S. heterolobus ate similar prey in similar proportions; the three dussumierid species (Spratelloides) ate smaller zooplankton and a greater proportion of calanoids than the other species.The size of prey eaten differed greatly between baitfish species. A. zosterophora ate larger prey than other species. The two Stolephorus species ate similar‐size prey, which were larger than the prey of the three species of Spratelloides. Among the Spratelloides, S. delicatulus ate smaller prey than the other two species. All species differed in the size of calanoids, carids and brachyurans they ate. In all cases, prey differed more by the minimum dimension (width) than by volume. There were significant relationships between fish length and prey width and volume, except for Archamia. However, in terms ofvolume, the prey of Stolephorus increased with fish size at a much greater rate than in Spratelloides species.Baitfish diets were compared to the zooplankton available. Prey selection by the three Spratelloides species and two Sfolephorus species was density‐dependent for all common prey types, although Stolephorus positively selected hyperiid amphipods and brachyurans. Archamia showed strong negative selection for calanoids and selected larger zooplankters, including fish larvae and carids, avoiding smaller, more common, prey.Overall baitfish density and zooplankton density did not correlate at either of the heavily fished sites. Nor were there consistent differences for any species in diet or changes in prey selection between the heavily fished and unfished sites. This suggests that, in these lagoons, commercial baitfish catches are not directly influenced by the composition or density of prey.
Biology of parasite populations: population dynamics of bothriocephalids (Cestoda‐Pseudophyllidea) in teleostean fish
Authors: Robert F. , Boy V. , Gabrion C. 
Published: January 2006

Relationships between sympatric populations of four species of Cestoda belonging to the genus Bothriocephalus (B. barbarus. B. gregarius, B. funiculus and B. scorpii) and populations of their respective hosts Scophthalmus rhombus, Pserra maxima, Ciliata mustela and Myoxocephalus scorpius were investigated. The parasites were overdispersed within their host populations. The mean intensities of B. burbarus were 1.59 (s.d.=0.83) in the Mediterranean (Gulf of Lions) and 1.25 (s.d.=0.53) in the Atlantic (coasts of Brittany). The mean intensities of B. gregarius were 62.3 (s.d.=49.7) in the Mediterranean and 14.06 (s.d.=18.48) in the Atlantic, compared to 1.78 (s.d.=0.3) for B. funiculus and 21.6 (s.d.=17.3) for B. scorpii.The distribution of prevalence of B. gregarius corresponded to a lognormal distribution while those of B. barbatus and B. fwticulus corresponded to negative binomials. No differences in infection could be related to host sex. The parasitization of B. gregariusdepended on host size. In brill, infection by E. barbatus was independent of host size and remained stable after the fish reached 180mm in length. Parasitization of turbot by E. gregarius was lower in young fish (≤110–150 mm) and increased with the host size. Compared to the Atlantic populations of B. gregarius and B. barbatus, the Mediterranean populations were more frequently and intensively infected. The differences in the population dynamics of B. gregarius and B. barbarus would appear to depend on whether or not the life cycle involves a paratenic host.
Vascularization and related distribution of leucocytes in carp, Cyprinus carpio L., head kidney
Authors: Imagawa T. , Hashimoto Y. , Kon Y. , Sugimura M. 
Published: January 2006

The distribution of lymphoid cells in the carp head kidney was investigated in relation to the vascular system. Blood vessels in the head kidney were histologically identified into arteries, sinusoids and two types of veins: renal veins and portal, which were distinguished by India ink injection into the caudal vein. By histological and histoplanimetrical observations it was found that the head kidney contained a number of lymphoid cells, which mainly aggregate around the connections between the portal veins and sinusoids, and that the cellular density of the aggregations was higher than in the thymus.Pigment‐containing cell clusters were also observed around these connections. This arrangement of the blood vessels suggests that it is one of the structures able to trap foreign materials, and the occurrence of the lymphoid clusters around the portal veins is a phylogenetic sign of the morphological division between granulopoietic and lymphatic tissues in the carp head kidney.
Growth and nutrient utilization by 0 + and 1 + triploid rainbow trout, Oncorhynchus my kiss
Authors: Oliva‐Teles A. , Kaushik S. J. 
Published: January 2006

Growth performance, protein and energy utilization in triploid rainbow trout juveniles of two yearclasses, 0 + and 1 +, were compared to diploid control groups. Growth rate, food conversion and protein efficiency ratios of triploid rainbow trout did not differ (0 + juveniles) or were slightly lower (1 + juveniles) than the diploid control. Proximate body composition was also not affected by ploidy.Apparent digestibility coefficients (ADC) ofprotein and ofenergy, oxygen uptake, and ammonia excretion rates were not different between the two groups. Nitrogen and energy balance studies showed that digestive and metabolic utilization of the diets did not differ in triploid and diploid rainbow trout juveniles.
Terrestrial locomotion in the climbing perch, Anabas testudineus (Bloch) (Anabantidea, Pisces)
Authors: Davenport J. , Matin A. K. M. Abdul 
Published: January 2006

Climbing perches use the tail for forward propulsion when on land. The spiny gill covers are used to obtain purchase on the substratum. Unusually amongst teleosts, the opercular and subopercular bone are not bound strongly together into a single operculum. Instead they are joined only by a thin, flexible membrane, so that the fish has two sections of the gill cover hinged separately; the opercular on the suspensorium and the subopercular on the rearmost part of the lower jaw. The gill covers open very widely and the subopercular rotates ventrally as well as laterally. Two modes of locomotion are employed. Usually Anabus adopts a near‐upright posture and alternately drives the left and right spiny suboperculars into the substratum, using the tail to vault over the subopercular (which acts in the manner of a short vaulting pole). During vigorous movement the fish may leave the substratum altogether during the vault. Fatigued fish, or fish which have fallen during climbing, move on their sides, using the tail for propulsion and a single spiny opercular which is repeatedly driven into the substratum. Maximum speeds observed on land corresponded to 1.8 body lengths S−1. No evidence of involvement of the pelvic fins in locomotion was obtained; the pectorals seemed only to help in tilting the head from side to side and did not contribute significantly to forward propulsion. On mud and tree bark the fish were laterally unstable, often resting on their sides. Grassy substrata provided support and permitted a more upright posture.Slope climbing ability was restricted to 25° when climbing tree bark and 30° when climbing grass. Coupled with lateral instability these observations disqualify the species from any tree‐climbing capacity. Anabas can climb vertical obstacles of at least half body length in height by pushing the head against the obstacle, using the spiny gill covers for purchase until one or other subopercular hooks over the top of the barrier. The subopercular is then used as a fulcrum for an upwards vault to clear the obstacle.
Early development of the digestive tract of cod larvae, Gadus morhua L., during start‐feeding and starvation
Authors: Kjørsvik E. , van der Meeren T. , Kryvi H. , Arnfinnson J. , Kvenseth P. G. 
Published: January 2006

Cod larvae, Gadus morhua L., were reared in the laboratory and released to a large marine enclosure 4 to 5 days after hatching (6–8° C). The development of the digestive system was studied until day 24 after hatching. Morphological investigations of the jaw apparatus and the digestive tract showed that the larvae are able to absorb ingested food well before exhaustion of the yolk sac. The foregut, and especially the midgut, were particularly active in lipid absorption, and the hindgut was characterized by pinocytotic activity. Duhng the first days of feeding, no distinct prey organisms were observed in the gut, and signs of food absorption in the epithelial cells of the gut were sparse.A distinct red fluorescence, restricted to the hindgut, was observed from day 11 to day 19. On the basis of changes in absorptive pattern in the gut we suggest that changes in digestive and absorptive abilities, as well as in nutritional needs, take place around days 15–17 after hatching.In starved larvae, signs of degeneration of the gut tissue were first visible in the foregut. By day 9 after hatching, microvilli was degenerated to such an extent that the ability to absorb food must have been severely restricted. If larvae are starved longer than this, they will probably not survive.
Critical swimming velocities of juvenile sockeye salmon and kokanee, the anadromous and non‐anadromous forms of Oncorhynchus nerka (Walbaum)
Authors: Taylor E. B. , Foote C. J. 
Published: January 2006

In streams tributary to the North Pacific, anadromous sockeye salmon and non‐anadromous kokanee, Oncorhynchus nerka (Walbaum), occasionally spawn sympatrically and male kokanee may act as 'sneaks’to spawn with the larger female sockeye. Despite this interbreeding, sockeye and kokanee exhibit persistent biochemical genetic differences at several enzyme loci. Genetic differences between forms may be maintained by selection against‘hybrids’due to the different life histories of sockeye and kokanee; sockeye make extensive smolt, oceanic, and spawning migrations while kokanee reside permanently in fresh water. We tested the sustained swimming abilities of juvenile sockeye, kokanee, and sockeye (female) × kokanee (male) hybrids to see if hybrids were inferior to sockeye in a trait that is probably under stronger selection in an anadromous life history. Sockeye had significantly greater mean critical swimming velocities (Ucrit) than kokanee of the same size raised under identical conditions (8.3 v. 7.3 body lengths s−1 respectively). When tested 1 month later the mean Ucrit of sockeye was only marginally greater than that for sockeye × kokanee hybrids (both c. 6.6 body lengths s−1). Sockeye swimming performance was also less variable than that of either kokanee or hybrids.Sockeye tended to have slimmer bodies and longer caudal regions than kokanee or sockeye × kokanee hybrids of the same size. Sockeye also had significantly more vertebrae than kokanee and hybrids, while hybrids had more vertebrae than kokanee. These morphological differences may have contributed to the differences in swimming performance. We concluded: (i) that juvenile sockeye and kokanee have diverged with respect to sustained swimming performance and that reduced performance by kokanee may be due to relaxed selection for sustained swimming performance associated with their non‐anadromous life history, (ii) that sockeye × kokanee hybrids appear to have modestly lower swimming capabilities than pure sockeye, and (iii) if the variability in swimming performance is associated with differences in survival in nature, then such differences may promote divergence between sympatric sockeye and kokanee.
Myxosporea parasites in roach, Rutilus rutilus (Linnaeus), from four lakes in central Finland
Authors: Brummer‐Korvenkontio H. , Tellervo Valtonen E. , Pugachev O. N. 
Published: January 2006

Ten myxosporean species belonging to three families were found in roach, Rutilus rutilus (Linnaeus), obtained in 1985 and 1986 from four lakes in central Finland which are connected to each other, but differ in water quality. One of the lakes is polluted by paper and pulp mill effluent, two are eutrophic and one is oligotrophic and still in its natural state. Eight species were found in all the lakes. The most common species were Myxidium rhodei Léger, 1905, Myxobolus muelleri Bütschli, 1882 and Myxobolus pseudodispar Gorbunova, 1936 with prevalences varying between 66–80, 16–31 and 32–59%, respectively, in the four lakes. The largest difference in myxosporean prevalence between lakes was found in the case of M. pseudodispar infection, which was highly significantly lower in the polluted lake. The locations of the myxosporean species in the tissues of the fish were found to be species‐specific. M. rhodei and M. muelleri being prevalent in the kidney and M. pseudodispar in the muscles.No clear seasonal variation was found but a tendency for a decrease in infection with increasing age was recorded in the case of M. rhodei and M. pseudodispar.
Fish species associations in riffle habitat of streams of varying size and acidity in New Brunswick and Nova Scotia
Authors: Peterson R. H. , Gale D. 
Published: January 2006

Factors related to stream size and alkalinity were most influential in determining fish species associations in three catchments of New Brunswick (NB) and Nova Scotia (NS) Canada, as determined by discriminant function analysis of TWINSPAN stream site classification.In the circumneutral Saint Croix (NB) catchment, the creek chub, Semotilus atromaculatus (Mitchill), brook trout, Salvelinus fontinalis (Mitchill), blacknose dace, Rhinichthys atratulus (Hermann), Atlantic salmon, Salmo salar Linnaeus, eel, Anguilla rostrata (Lesueur) and fallfish. Semotilus corporalis (Mitchill) dominated stream sites of progressively greater discharge and higher median mid‐summer temperature. In the acidic Gold (NS) system, the brook trout, Atlantic salmon, and eel exhibited a distribution pattern in relation to stream size and temperature similar to that for the Saint Croix, with the eel relatively more abundant in the Gold at large stream sites. The creek chub was excluded from the smallest tributaries by low pH. The ranges of blacknose dace and fallfish do not extend to southwestern Nova Scotia. In the Medway (NS) system (slightly more acidic than the Gold), the relative abundance of Atlantic salmon is reduced, and that of eel increased as compared with the Gold and Saint Croix systems. The lower limiting mid‐summer pH levels for creek chub, salmon, brook trout, and eel are 5.2, 5.0, 4.7 and <4.5 respectively.
Food intake and growth in the Moses perch, Lutjanus russelli (Bleeker), with reference to predation on penaeid prawns
Authors: Smith R. L. , Salini J. P. , Blaber S. J. M. 
Published: January 2006

Juvenile Moses perch were fed various rations of penaeid prawn and pilchard foods at 26.4 and 28.7° C to elucidate feeding–growth relationships. Maintenance rations amounted to 5.0 and 3.8% of body weight per day (BW day–1) on prawn and pilchard diets, respectively, at 26.4° C and 4.5% BW day 1 for prawn at 28.7° C. This apparent reduction in maintenance ration at higher temperature is probably due to reduction in activity levels. Starvation weight loss, an indicator of resting metabolic rate, increased with temperature and exhibited a Q10 of 2.0 to 2.4.Fish fed ad libitum once or twice per day at 26.4° C grew at 1.1 % BW day–1 and ingested about 9% of their BW day–1. At 28.7° C fish ingested about 8% of their BW day–1 and grew 1 .0% BW day–1. These growth rates are comparable to those of similar sized lutjanids in the wild. Since prawns comprise 64% of the diet of Moses perch in northern Australia, this level of consumption would require about 6% BW day–1 of prawns. The relevance of these findings to the assessment of predator impact on prawns in Australian estuaries is discussed.
Changes in plasma protein patterns in smolting Atlantic salmon, Salmo salar L., are not dependent on changed growth rates
Authors: Rourke A. W. , Saunders R. L. , Harmon P. R. 
Published: January 2006

Juvenile Atlantic salmon, Salmo salar L., were raised under simulated natural photoperiod (SNP) and constant light (CL). SNP fish displayed typical characteristics of smolts in the spring including changes in colouration, elevated gill Na+/K+ ATPase activity and ability to pass a seawater challenge. CL fish grew at rates comparable to SNP fish, but did not demonstrate any of these molt characteristics.Electrophoretic analyses of plasma proteins from both groups of fish revealed that SNP fish displayed reproducible qualitative changes in protein patterns from February to May with May patterns being the most complex. CL fish displayed patterns similar to SNP fish. The timing of the appearance of patterns was influenced by photoperiod as indicated by the fact that CL fish had a progression of pattern changes retarded by at least one month relative to SNP fish. The changes in plasma protein patterns in smolting Atlantic salmon were not dependent on changed growth rates.