bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Hook Size in the Hawaiian Deep-sea Handline Fishery
Authors: Ralston Stephen
Published: April 2011

Experimental bottom fishing trials were conducted in the Northwestern Hawaiian Islands where four different hook sizes (Nos. 28, 30, 34, and 38) were fished simultaneously. Within this series the biggest hook is about 71% larger than the smallest hook. Alterations in gear within this range have no substantive effect on the catch of bottom fish. In all cases examined, variation in catch statistics associated with differing replications (days and sites) greatly exceeded any effect attributable to different hook sizes. It is concluded that for medium- and large-sized fish, the catch is reasonably representative of those fish which strike the hooks and that a sigmoid selection curve most accurately describes the selective properties of the gear in this fishery.Key words: gear selection, hook size, bottom fish, replications
Capacity Reduction on Norwegian Industrial Fisheries
Authors: Flåm S. D. , Storøy S.
Published: April 2011

Catch and processing capacity in Norwegian industrial fisheries may be extensively reduced without affecting gross revenue. A linear programming model for maximizing annual revenue in the Norwegian industrial fisheries was formulated. The main purpose of the modeling effort was to determine the minimal size of the fleet and the industry. The constraints of the model are on catch and on capacity in fishing, transporting, and processing.Key words: linear programming, capacity reduction.
Manipulation of the Seasonal Reproductive Cycle of the Landlocked Atlantic Salmon (Salmo salar) by LHRH Analogues Administered at Various Stages of Gonadal Development
Authors: Crim L. W. , Evans D. M. , Vickery B. H.
Published: April 2011

Pellets designed for continuous, long-term, oligopeptide, hormone delivery were implanted into the adult landlocked Atlantic salmon (Salmo salar) to investigate the effects of LHRH agonist analogue (LHRH-A) upon the reproductive system. Chronic elevations in plasma gonadotropin were observed in experimental fish at a variety of stages of reproductive development. Synthesis of pituitary gonadotropin was also evoked in sexually regressed fish and fish undergoing gonadal recrudescence, but the already elevated level of pituitary GtH observed in prespawning and spawning salmon was not augmented. In prespawning fish, the events of ovulation and spermiation were accelerated by LHRH-A treatment. The LHRH-A hormone treatment also increased milt volume and the duration of spermiation in ripe males. In sexually regressed males LHRH-A treatment did not induce the advanced phases of spermatogenesis but some testicular stimulation was indicated by the presence of increased numbers of B-type spermatogonia and enlargement of the lumen of lobules. The gonadal response to LHRH-A treatment during the rapid phase of gonad recrudescence differed in males and females. Based upon the changes in GSI, the LHRH analogue accelerated vitellogenic development of the ovaries in females; in males, however, the GSI was significantly reduced following LHRH-A administration. Whereas, it seems clear that a long acting preparation containing LHRH-A can be successfully used in prespawning fishes to advance the final events of gonadal maturation and initiate spawning, further studies are necessary to evaluate the potential of LHRH agonists to either stimulate or inhibit the reproductive development of fish at other stages of the seasonal reproductive cycle.Key words: fish, teleosts, landlocked salmon, LHRH analogues, gonadotropic hormone releasing hormones, seasonal reproductive cycle, gonad development, spawning
Patterns and Rates of Nitrogen Release by Benthic Chironomidae and Oligochaeta
Authors: Gardner Wayne S. , Nalepa Thomas F. , Slavens David R. , Laird Gwenyth A.
Published: April 2011

Metabolic mineralization of ammonium by tubificid worms and chironomid larvae appears to be an important mechanism contributing to nitrogen regeneration from aerobic lake sediments. Mean weight [ash free dry weight (AFDW)] – specific ammonium release rates ranged from 3 to 15 nmol NH4 (mg AFDW)]−1∙h−1 for chironomid and tubificid species collected at different times and temperatures from nearshore Lake Michigan sediments. Although mean rates of nitrogen release were similar for the two groups of benthic invertebrates, the patterns of release were different. Tubificids released nitrogen (ammonium plus primary amines) continuously, whereas chironomids released it in spurts several times per hour. Mean ammonium-release rates were generally constant with time after the animals were removed from food for both species. This implies that ammonium regeneration for these benthic animals is primarily an endogenous process. Conversely, primary amine nitrogen release often decreased with time after food removal and may reflect either egestion of partially digested materials from the animals' guts or a decrease in the metabolic pool size of free amino acids. Based on previous measurements of phosphorus release, mean molar NH4:PO4 ratios in excreted materials were calculated to be 15:1 for chironomids and 35:1 for tubificids.Key words: nitrogen release, benthic invertebrates, chironomids, tubificids, ammonium excretion, amino acid release
Primary Productivity in a Large, Temperate Lake with River Interflow: Kootenay Lake, British Columbia
Authors: Jasper Steve , Carmack Eddy C. , Daley Ralph J. , Gray Colin B. J. , Pharo Chris H. , Wiegand Ron C.
Published: April 2011

Phytoplankton productivity in a large, deep lake with river interflow was determined using an incubator method modified to include vertical distributions of chlorophyll and temperature together with continuous surface irradiance measurements. The annual average areal production, in 1977, was 170 g C∙m−2 with daily areal productions ranging from 100 to 2800 mg C∙m−2. Pmax for all samples correlated well with chlorophyll a (r = 0.79). No large horizontal trends in areal productivity or Pmax were found in the lake at any time of the year. However, pronounced differences with depth in the photosynthetic characteristics of populations within the euphotic zone were common during the stratified season. The two large inflowing rivers are thought to be important to the productivity of Kootenay Lake as they initiate the spring production peak and supply nutrients to the deeper phytoplankton populations during the summer and fall period.Key words: phytoplankton, productivity, incubator, riverine lake, vertical structure
An Investigation of the Relationship Between Oregon Coho Salmon (Oncorhynchus kisutch) Hatchery Releases and Adult Production Utilizing Law of the Minimum Regression
Authors: Clark Jerry , McCarl Bruce
Published: April 2011

This study examines aggregate relationships between coho salmon (Oncorhynchus kisutch) adult production and hatchery releases within the Oregon Index Area (OIA). Previous analyses have indicated the presence of density dependence, and concluded with a request for a reduction in hatchery smolt releases. The hypothesis that density dependence is exhibited in the OIA is tested via a broad correlation approach. Several regression models are used including one unique one in fisheries research based on limiting factors.Analysis was done on the fitted regression equations including a simple simulation of release policies. Neither significant density dependence nor a statistically supportable technical maximum for smolt releases was found. The limiting factors regression technique generally gives the best results of all the models employed, and thus appears potentially useful in this type of fisheries work.
Reproductive Success of Artificially Hybridized Golden Trout (Salmo aguabonita) and Rainbow Trout (Salmo gairdneri)
Authors: Halliburton Richard , Pipkin R. E. , Gall G. A. E.
Published: April 2011

Golden trout (Salmo aguabonita) were artificially crossed to hatchery rainbow trout (S. gairdneri). Interspecific matings were as fertile as intraspecific matings, and hatchability and survival to 35 d were not significantly different among the mating types. Embryos derived from golden trout eggs hatched sooner than those derived from rainbow eggs, and G♂ × R♀ hybrids were significantly larger than golden trout or rainbow trout at 165 d. Hybrid males were significantly more fertile than golden trout or rainbow trout males, and hatchability of the eggs from hybrid females was significantly higher than that of eggs from golden trout females. However, this apparent hybrid superiority may not be genetic. The results suggest that postzygotic reproductive isolating mechanisms between the two species are very weak or nonexistent, at least through the F1 generation.
Importance du régime de dénudation sur la structure et la succession des communautés intertidales de substrat rocheux en milieu subarctique
Authors: Archambault Diane , Bourget Edwin
Published: April 2011

Developmental patterns were studied following natural (abrasion by ice) and experimental disturbances (total or partial clearings) in intertidal rocky communities. Four semi-exposed communities along the St. Lawrence Estuary and Gulf were studied from May 1977 to May 1979. In the spring, when free space becomes available, annual algae, mainly Ulothricales and Ulvales, rapidly colonize areas denuded by ice abrasion. This early stage is soon followed by an abundant fucoid growth, largely Fucus vesiculosus but also some Ascophyllum nodosum, and a large number of Balanus balanoides, along with some Mytilus edulis. Opportunists, F. vesiculosus and B. balanoides, dominate where ice disturbances are severe and regular but where the community is not severely disturbed, initial differences in the abundance of F. vesiculosus and A. nodosum are reduced, and the community becomes closer to the mature one dominated by A. nodosum. The period of disturbance influences the species' settling and their abundance. The earlier the disturbance in the spring, the greater will be the colonization by the opportunists Ulothricales, Ulvales, and B. balanoides, but when the disturbance occurs later, F. vesiculosus and M. edulis are the main settlers. The tidal level influences mainly the establishment of dominance. In the mid zone, few species are present, densities are low, competition is not an important controlling factor, and Balanus dominate. In the low zone, barnacles are replaced by mussels, the number of species and densities are high, and competition is greater. Exclosure and enclosure experiments using cages have shown that littorinid grazers have a negligible influence on the reduction of the dominant annual alga Ulothrix flacca. Its reduction in midsummer appears to be related to its life cycle. Predators were rarely observed at the study sites. Structural and developmental patterns of intertidal rocky communities were slow and the monopolization of space by A. nodosum and M. edulis, as observed in the mature, less disturbed community, must result from a long period [Formula: see text] without major disturbances.
Factors Governing Geographical Variation in Body Size of Diaptomus minutus (Copepoda, Calanoida)
Authors: Carter J. C. H. , Sprules W. G. , Dadswell M. J. , Roff J. C.
Published: April 2011

Considerable variation in cephalothorax length of adult female Diaptomus minutus and D. oregonensis occurs among lakes of glaciated eastern North America during spring and early summer. Moderately significant Spearman rank correlations existed between D. minutus length, and Secchi transparency depth (negative) and true water color (positive). Similar significant correlations were not found for D. oregonensis. In these lakes water transparency is largely a negative function of color derived from humic substances. It is hypothesized that waters of low transparency provide a measure of protection to D. minutus against visually feeding fish predators. It can thus undergo a modest gain in size, thereby reducing vulnerability to invertebrate predation, increasing potential fecundity and (possibly) allowing it to feed on larger food particles.
Suspended Sediment Transport and Deposition Modeling in the Bay of Fundy, Nova Scotia — a Region of Potential Tidal Power Development
Authors: Greenberg D. A. , Amos C. L.
Published: April 2011

Two recent independent studies of the Minas Basin have been combined to produce a numerical simulation of suspended sediments. One study devised a numerical, barotropic tidal model of the Bay of Fundy and Gulf of Maine, which produced a good simulation of the tides and currents in the Minas Basin. The second, an extensive program of sediment sampling and monitoring addressed the nature of suspended sediments, bottom sediments, their various sediment sources and the postglacial evolution of the system. The only significant source of suspended sediment was from the open boundary to the Minas Basin and was of relatively uniform concentration through the water column. Consequently, the barotropic tidal model was well suited to modeling this material. Sediment laws describing sediment settling, resuspension, and the critical stress for entrainment were obtained from the literature and evaluated. The settling velocity of the suspended sediment was obtained by experimentation using actual water/sediment samples. Because the various parameters and critical stresses show a considerable variation among experimenters, runs were planned to examine a range of parameters. A close fit to existing conditions was obtained with the model generating mudflats in those regions where indeed they exist. Using the various parameters and critical stresses reflecting maximum sedimentation, the model was run to include the effects of a tidal power barrage off Economy Point. It is concluded that suspended sediment would not inhibit the operation of such a barrage through siltation directly in front of or behind the barrier. Increased siltation can be expected in the intertidal areas behind the barrage. Sediment budget considerations further limit the degree of post barrier siltation, insofar as the resident volume of suspended material (30 × 106 m3) is not enough to significantly reduce the headpond area.Key words: suspended sediment, sediment transport, numerical model, tide
River-Dominated Suspended-Sediment Deposition in a New Mississippi Delta
Authors: Heerden Ivor Ll. van , Wells John T. , Roberts Harry H.
Published: April 2011

Progradation of Atchafalaya Delta, one of the most dynamic geological events in historical times within the Mississippi Delta complex, has produced a 230 km2 new sediment body on the Louisiana coast of which 28 km2 is subaerial. Sedimentation in Atchafalaya Bay was initiated in the early 1950s, and by 1973 a complex subaerial feature had evolved. Between 1972 and 1980 the area of Atchafalaya Delta dominated by coarse sedimentation increased. The greatest increase occurred along the delta's western flank as a result of introduction of dredge spoil from a navigation channel, as well as greater discharges in this area. Detailed field studies in the natural (spoil-free) eastern Atchafalaya Delta show that discharge and suspended load vary greatly between flood and nonflood conditions. Recognition of sedimentary environments, each characterized by sedimentary structures and grain size, indicates rates and modes of deposition. Processes of deposition in this fluvially dominated environment are characterized by rapid settling of suspended loads generally under waning flood conditions.Key words: new Mississippi delta, Atchafalaya River, suspended sediment, river-dominated deposition
Characteristics of Suspended Cohesive Sediment of the Severn Estuary, U.K.
Authors: Bryant R. , Williams D. J. A.
Published: April 2011

Characteristics of suspended cohesive sediment from the benthic boundary layer of the Bristol Channel/Severn Estuary were examined at one location (51°27.66′N. 2°53.20′W). Samples were collected in vertical profiles over the bottom 2 m of the water column at times near to, and at low and high slack water periods on spring and neap tides. Primary particle size distributions obtained using a Coulter Counter (range 1.59–50 μm) and electron microscopy (range 0.1–20 μm) reveal bimodal (volume) frequency distributions with a lower mode fixed at 1.59 μm and a higher mode variable between 6 and 30 μm. When these data are converted to number frequency distributions, the higher mode effectively vanishes, while the lower is retained. Suspended sediment mineralogy, of dispersed samples, was determined by individual and multiple particle examination using analytical electron microscopy. Average suspended sediment composition was found to be illite 44%, quartz 23%, chlorite 19%, calcium carbonate 5%, kaolinite 4%, and organic carbon 3% (by weight). Floc diameters estimated from hindered settling experiments were ≈ 140 μm possessing a sedimentation velocity in the range 1.8–2.0 mm∙s−1, in good agreement with field observations of temporal changes in the vertical distribution of turbidity.Key words: suspended cohesive sediment, flocculation, Bristol Channel.
Ichthyoplankton Associated with a Warm Core Ring off the Scotiars Shelf
Authors: Wroblewski J. S. , Cheney Jerry
Published: April 2011

A warm core ring and adjacent waters off the Scotian Shelf in June 1982 contained substantial numbers of larval and juvenile white hake, Urophycis tenuis, as far as 140 km seaward of the continental shelf break. The warm core ring, designated 81-G, had entrained shelf water on several occasions before the shipboard observations were made. We suggest that the ring contributed to the offshore advection of these fish, which probably were spawned on the continental shelf or upper slope. Warm core rings can disrupt the usual larval drift pattern of shelf–slope fishes and thereby affect recruitment. Larvae and juveniles of several species of tropical–subtropical fishes found in ring 81-G have been reported previously as rare specimens in ichthyoplankton surveys on the Scotian Shelf. Our observations support the hypothesis that warm core rings can be a mechanism for transport of these expatriated fishes onto the shelf.
Characterization of Protease from the Myxosporean Salmon Parasite, Henneguya salminicola
Authors: Bilinski E. , Boyce N. P. , Jonas R. E. E. , Peters M. D.
Published: April 2011

The biochemical properties of the protease(s) from the myxosporean parasite, Henneguya salminicola, occurring in the muscle of sockeye salmon, Oncorhynchus nerka, were examined. The cysts of the parasite contained a soluble, heat-labile protease, having maximal activity at pH 3.0 for hydrolysis of hemoglobin and 4.5 for hydrolysis of salmon muscle proteins. The inhibitions obtained from metal ions and from sulfhydryl group binding reagents suggest the involvement of sulfhydryl groups in the expression of enzyme activity. The enzyme required no preliminary activation by disulfide bond reducing agents and it had no obvious divalent metal ions requirement. The hydrolysis of salmon muscle by H. salminicola protease was strongly temperature dependent. Although proteolysis occurred at the highest rate at 30–40 °C, the enzyme remained active in iced muscle. The proteolytic activity was arrested completely in frozen muscle but the enzyme was only slightly inactivated by a prolonged frozen storage (−28 °C). The presence of the parasite had no marked effect on the texture of raw or cooked flesh.
Vertical Distribution of Atlantic Halibut (Hippoglossus hippoglossus) Eggs
Authors: Haug Tore , Kjørsvik Elin , Solemdal Per
Published: April 2011

It is suggested that the vertical distribution of Atlantic halibut (Hippoglossus hippoglossus) eggs is determined by their specific density and that it is closely correlated to seawater salinity. In two deep North Norwegian fjords, only one halibut egg was found near the bottom (approximately 5200 m3 seawater filtered), while 278 eggs were found floating pelagically in intermediate water layers (approximately 190 000 m3 seawater filtered). Eggs were most abundant in water masses where temperature and salinity ranged between 4.5 and 7.0 °C and 33.8 and 35 0‰. Neutral buoyancy salinity measurements of living eggs corresponded approximately with the observed capture salinities. Mean capture salinity was 34.2 ± 0.3‰ (Malangen) and 34.5 ± 0.4‰ (Sørøysund). Egg diameters ranged from 3.06 to 3.49 mm.
Reproductive Biology of Pacific Herring (Clupea harengus pallasi)
Authors: Hay D. E.
Published: April 2011

Most British Columbia herring begin sexual maturation in the late summer and become sexually mature in the subsequent March or April. As they mature, most stocks migrate from summer feeding grounds to overwintering areas and then to shallow nearshore spawning areas. Also, newly recruited, sexually maturing fish join the adult spawning stocks, either on the summer or winter grounds. These events occur in an unpredictable environment. Consequently, reproduction in Pacific herring (Clupea harengus pallasi) may be viewed as a biological problem of maintaining synchrony and precision: specifically the synchronous maturation of (1) males and females and (2) the recruit spawners with the adult fish that have spawned in previous years. Biological precision is required to ensure that gametes are released at the correct place at the correct time. Further precision is required to achieve an appropriate balance between egg number and egg size, and then to control the density of eggs deposited on the bottom. The annual temperature regime is a vital regulator of these processes. Generally, the warmer the temperature, or lower the latitude, the earlier the maturation and spawning time. There are some notable exceptions that indicate local adaptation to other environmental cues. Also, experimental work indicates that food supply can affect the maturation rate. Intensities of egg depositions are generally similar among Pacific North American stocks, and indeed for many documented herring spawnings from Asian and European stocks. It has been shown that eggs in the middle of very thick spawns have lower survival so there is a selective advantage for biological mechanisms that ensure more even and lighter egg densities. This paper suggests that egg density in Pacific herring is controlled by a biological feedback mechanism involving milt concentration and hydrographic factors. Earlier spawners tend to be larger and there is a positive relationship between female size and egg size, a tendency consistent with other herring stocks and species. Size-adjusted fecundity, when compared among different regions and years, is strikingly uniform within British Columbia. On a broad geographic scale (California to Alaska), size-specific fecundity declines with latitude. Recent experimental work reveals that total egg number is higher at early stages of maturation and decreases as spawning time approaches. Presumably, this decrease reflects selective resorption of some developing oocytes, and probably occurs in response to available body energy. The duration and geographical variation in spawning time is relevant to questions concerning the evolutionary and taxonomic relationships between Pacific herring and Atlantic herring (Clupea harengus harengus). Other aspects of reproductive biology have important management implications, particularly for (1) predicting recruitment, (2) deriving stock estimates from spawn surveys, and (3) managing fisheries.
Recent Changes in the Central and Southern North Sea Herring Stocks
Authors: Burd A. C.
Published: April 2011

Since 1980 there has been a sudden recovery of recruitment to the central and southern North Sea herring stocks (Bank and Downs, respectively). In contrast, recruitment to the northern North Sea has continued at a low level and spawning stock biomass has even declined since 1979. These events underline the independence of the substocks in the North Sea, each of which has reacted differently to the cessation of the directed herring fishery in the North Sea since 1977. A precondition to the reopening of a herring fishery in the North Sea was that the severely depleted spawning stock biomass should have recovered to 800 000 t, the underlying assumption being that all components would respond in a similar manner and that a reopening of the whole North Sea would be possible. This has not happened and it may well be that management of the North Sea as a single unit is not a viable management procedure. The paper examines the historic changes in sizes of the Bank and Downs stocks, with particular emphasis on the most recent period. Evidence of density-dependent growth change is considered together with the recent data on fecundity and larval herring production. It is concluded that if the separate stocks are to be managed individually for maximum yield, then global North Sea regulations such as a total allowable catch and size regulation are inappropriate. Regulations must also take into consideration the seasonal distributions of the stocks. Indeed, this would lead, in particular, to more restrictive and specific regulation of the industrial fisheries.
History of the Herring Fishery and Review of Artificial Propagation Techiques for Herring in Japan
Authors: Morita Shou
Published: April 2011

According to written records, a Japanese herring fishery has been carried out since 1447, but statistical catch data were not recorded until 1870. The Japanese herring fishery has harvested the so-called Hokkaido spring herring, which spawned near the coast of Hokkaido from March to May. In 1897, the landings reached a peak of 975 000 tonnes but the resources were depleted year by year and this stock became extinct in the 1950's. During the 1960's, Japanese fleets were exploiting the herring stocks in the Northwest Pacific. However, since 1970 these fisheries were limited in their operations by the Japan–Soviet Fisheries Committee and eventually ceased in 1976. At the present time, the Japanese catch of herring is at a low level of several thousand tonnes. The Japanese license system was not designed to conserve the resources, and herring studies were weighted to fishing forecasts only. Many Japanese scientists believed that the strength of herring year-classes fluctuated with changes in food conditions in the early larval stages. Based on artificial egg production techniques developed recently in Japan, herring eggs were successfully hatched, and larvae were cultured artificially and raised to 66.3-mm juveniles with a high survival rate.
Intervention Analysis of Power Plant Impact on Fish Populations
Authors: Madenjian Charles P. , Jude David J. , Tesar Frank J.
Published: April 2011

Alewife (Alosa pseudoharengus) and yellow perch (Perca flavescens) abundances, estimated from monthly gillnet and trawl catches at two transects, were monitored before (1973–74) and during (1975–82) operation of the D. C. Cook Nuclear Power Plant, southeastern Lake Michigan. Intervention analysis, a technique which accounts for autocorrelated observations, and analysis of variance (ANOVA) were applied to the monitoring data to assess any plant impact beginning in 1975. Both analyses disclosed no significant power plant impacts except for gillnetted yellow perch adults. The ANOVA indicated a significant decrease in abundance at the plant-discharge transect relative to the reference transect as plant operation began, which established a plant effect; intervention analysis showed no change. When April and May catches (months of low abundance) were deleted, this plant effect was insignificant. Monte Carlo simulation showed that as the first-order autoregressive coefficient increased positively, type I error of the ANOVA F-test increased. However, ANOVA was more powerful than intervention analysis when a first-order autoregressive component was included. Impact assessment based only on ANOVA can result in detection of impact when actually there was no effect (type I error) when observations are serially correlated (lack independence).
Effects of Diet on PCB-Induced Changes in Xenobiotic Metabolism in the Liver of Channel Catfish (Ictalurus punctatus)
Authors: Ankley Gerald T. , Blazer Vicki S.
Published: April 2011

Effects of nutrition on xenobiotic-metabolizing enzymes in fishes are not well known. We fed three groups of channel catfish (Ictalurus punctatus) either a synthetic, laboratory-prepared diet or one of two commercial catfish rations. After 3 mo on each diet, fish were treated with the enzyme inducer Aroclor 1254. Hepatic microsomal monooxygenase (MO) activity was lower in untreated fish fed a commercial diet than in those fed the laboratory diet. Aroclor 1254 increased MO activity to a lesser degree in fish fed that same commercial diet compared with those receiving the laboratory or other commercial diet. Hepatic microsomal UDP-glucuronosyltransferase (UDPGT) activity was similar in all control fish; however, Aroclor 1254 increased UDPGT activity to differing degrees in the three diet groups. Hepatic cytosolic glutathione S-transferase (GST) activity was increased by Aroclor 1254 to a similar extent in all diet groups; however, levels of GST activity generally were higher in fish fed the commercial diets than in those fed the laboratory ration. These data indicate that diet can affect the toxicity of xenobiotics to fishes through alterations in hepatic enzyme systems, and thus should be considered a potential source of variation in toxicological studies with fishes.
A Reevaluation of the Search Cycle of Planktivorous Arctic GraylingsThymallus arcticus
Authors: Evans Barbara I. , O'Brien W. John
Published: April 2011

Planktivorous arctic grayling, Thymallus arcticus, were previously believed to forage using a cruise strategy, searching for prey while swimming, while other planktivores have been found to search while stationary, a strategy termed "saltatory search." Comparing the predicted components of cruise and saltatory search, we observed that the planktivorous feeding behavior of the grayling was more consistent with the strategy of saltatory search. Although the grayling appear to swim continuously, they actually pause before making turns. Swim speed is reduced with decreased prey detectability, as would be expected of a cruise searcher; however, this behavior is believed to be a result of fin placement and body form constraints. Pause duration, run length, and run turn angle were observed to vary when grayling fed on prey of different sizes, all in a manner consistent only with saltatory search. The relationship between the ability to locate prey and the components of search suggests that the grayling alter the way they search for different prey, possibly as a means of increasing search efficiency.
A Diver Operated Suction Gun and Collection Bucket for Sampling Crayfish and Other Aquatic Macroinvertebrates
Authors: Davies I. J. , Ramsey D. J.
Published: April 2011

A suction gun powered by rubber tubing and a collection bucket with a self-closing lid were developed to assist SCUBA divers in sampling crayfish. Design details of the equipment are reported. Test collections done by hand and with the suction gun each contained a full size range of crayfish and equal proportions of male and female specimens. By comparison, females, young-of-the-year, and juvenile crayfish were poorly represented in catches from baited wire traps. Divers found that using the suction gun was easier, faster, and less damaging to specimens than collecting by hand.
Correction of Relative Fish Abundance Estimates from Catch Data for Variable Fishing Intensity during Lake Surveys
Authors: Ryan P. M. , Kerekes J. J.
Published: April 2011

Six small Newfoundland lakes were fished with gillnets over a 3–6 yr period in a manner typical of standard lake surveys where surveyors have a fixed amount of gear available, but lake size varies. Catch and effort data for brook trout (Salvelinus fontinalis) were examined for the purpose of selecting an appropriate measure of the relative abundance of trout. Fishing effort was not a function of lake area but fishing intensity or fishing effort per unit area varied inversely with lake area. Brook trout yield (kilograms per hectare) was positively related to fishing intensity Catch per unit effort (kilograms) of brook trout was inversely related to fishing intensity. Methods are suggested to correct for the bias in catch data resulting from variable fishing intensity during lake surveys and improve the recognition of differences in relative fish abundance.
Mercury in Crayfish Species from Thirteen Ontario Lakes in Relation to Water Chemistry and Smallmouth Bass (Micropterus dolomieui) Mercury
Authors: Allard Martine , Stokes Pamela M.
Published: April 2011

Total mercury was determined in crayfish from 13 lakes in South-Central Ontario that receive no direct discharge of mercury to their watersheds. Mercury concentration in crayfish abdominal muscles ranged from 0.022 to 0.614 μg∙g−1 wet weight and was positively related with weight in Cambarus bartoni, C. robustus, Orconectes obscurus, O. propinquus, and O. virilis. Bioaccumulation of mercury in the early maturing and comparatively small body-sized O. propinquus was faster than in any other species. There were significant differences in mercury concentrations in crayfish among the lakes. Conductivity of lake water alone explained 54% of the variability observed among lakes for mercury in abdominal muscle of a 10-g crayfish. Moreover, mercury levels in C. bartoni and C. robustus were significantly higher in lake inlets than in the corresponding lake basin. Mercury in smallmouth bass was also positively correlated with crayfish mercury. From these results, we conclude that high mercury concentrations in biota were related to low mineralization of lake or inlet water and to the sensitivity to acidification. We also recommend that crayfish be used as biomonitors of mercury in addition to proving useful toward a better understanding of mercury pathways in these remote lakes.
Plasma Antifreeze Levels Reflect the Migratory Behaviour of Atlantic Herring (Clupea harengus harengus) in the Southern Gulf of St. Lawrence
Authors: Chadwick E. M. P. , Cairns D. K. , Dupuis H. M. C. , Ewart K. V. , Kao M. H. , Fletcher G. L.
Published: April 2011

This study compared freeze protection conferred by blood antifreeze proteins to juvenile and adult Atlantic herring (Clupea harengus harengus) in the southern Gulf of St. Lawrence in December 1988. Juvenile herring had significantly lower plasma freezing points and significantly higher antifreeze activity than adults. Differences in antifreeze activity and in late autumn distribution suggest that juvenile herring are more capable of wintering in the Gulf of St. Lawrence than adults. This conclusion is consistent with our observation that during December, juveniles were present in shallow waters of Chaleur Bay, which is ice-covered during winter, while adults were found only in the deeper waters of Sydney Bight, which do not freeze during winter.
Effect of an External Tag on Growth of Sabiefish (Anoplopoma fimbria), and Consequences to Mortality and Age at Maturity
Authors: McFarlane Gordon A. , Beamish Richard J.
Published: April 2011

Tagged juveniles from a strong year-class of sablefish (Anoplopoma fimbria) were sampled for 9 yr Tagged females were approximately 6 cm larger than untagged females at 50% maturity. Males showed little difference because of their slower growth rate. Untagged males and females matured one and 2 yr earlier than tagged males and females. From this same year-class length-at-age of untagged males and females was significantly larger than for tagged and recaptured fish. Untagged males and females were 6.5 and 8 cm larger than tagged fish by age seven. Smaller tagged fish were recaptured at lower rates than larger tagged fish, indicating that slower growth reduced recapture percentage, which we believe indicates a higher mortality rate. Because smaller size was associated with increased mortality and tagged fish grew slower than untagged fish, we concluded that tagged fish had higher rates of mortality than untagged fish. The increased age and size at 50% maturity and the increased juvenile mortality indicated the potential response of a population of sablefish and possibly other species to a reduction in individual fish growth. If our results apply to other species and other types of tags, investigators should be cautious in extrapolating from tagged to untagged populations.
Comparison of Logistic Regression and Discriminant Analyses for Stock Identification of Anadromous Fish, with Application to Striped Bass (Morone saxatilis) and American Shad (Alosa sapidissima)
Authors: Prager Michael H. , Fabrizio Mary C.
Published: April 2011

We examined the applicability of logistic regression to stock identification studies and compared its performance on two data sets to that of linear and quadratic discriminant functions. Logistic regression can be used to model a categorical dependent variable associated with continuous or discrete independent variables, and is preferred to discriminant analyses when the explanatory variables are not multivariate normal. Our examples were American shad (Alosa sapidissima) from the Connecticut River and Hudson River estuaries, and striped bass (Morone Saxatilis) from the Hudson River, Chesapeake Bay, and Roanoke River estuaries. In the examples we used a resampling method to assess classification and allocation errors of the two methods on new data. For the shad data, the logistic model classified significantly more fish correctly, and provided a significantly better estimate of stock composition. For the striped bass data, the two methods classified about the same proportion of fish correctly, but the logistic model gave a significantly better estimate of stock composition.
Measurement of Scope for Change in Ascendency for Short-Term Assessment of Community Stress
Authors: Genoni Giulio P. , Pahl-Wostl Claudia
Published: April 2011

Scope for growth, or the resource balance of an organism or population, has been used as a comparative descriptor for the short-term assessment of stress effects. This concept may be extended to all levels of biological organization, and in particular to the assessment of early responses of communities to anthropogenic stress (or subsidy). The size (throughput) and development (organization) of a biological system can be described by the state function ascendency. We define the scope for change in ascendency of a biological system as the difference between the ascendency of inputs and the ascendency of outputs. This balance increases when a resource subsidy is used by the system to build size and organization, and decreases under stress. Changes in a system's resource balance and distribution in terms of flows help trace effects at one level to effects at the other. Computer simulations of an epilimnion community indicated that scope for change in ascendency gives a sensitive and fast response to perturbations. This index may provide a means for short-term assessment of anthropogenic stress, or management options.
Response of a Phytoplankton Community to Controlled Partial Recovery from Experimental Acidification
Authors: Findlay D. L. , Kasian S. E. M.
Published: April 2011

Lake 223 was experimentally acidified with H2SO4from 1976 to 1989. The pH was reduced from 6.7 (1974) to 5.0 (1981) and held there for 3 yr (1981–83). Beginning in 1984 the pH was allowed to increase at a controlled rate by reduction of acid additions, resulting in a two-step recovery of 4 yr at pH ~5.5 and 2 yr at pH ~5.8. During the first 6 yr of early recovery, species diversity of the phytoplankton community increased linearly with pH and the number of common species increased. Total phytoplankton biomass remained elevated above preacidification estimates or increased. Dinoflagellates and cyanophytes remained codominant with little evidence of other taxonomic groups increasing.
Hatchery Growth of Pure Strains and Intraspecific Hybrids of Juvenile Arctic Charr, Salvelinus alpinus (Canadian × Norwegian Charr)
Authors: March B. G. E. de
Published: April 2011

Growth parameters of 36 tank populations representing 23 full-sib families of Nauyuk and Norwegian Arctic charr (Salvelinus alpinus) and both reciprocal hybrids were determined for 1 yr. Hatching success of families was a maternal characteristic. Mean weights of families at 30 d after swim-up were related to maternal effects as well as the general and specific combining abilities of the two strains, with the weight contribution of the Nauyuk parent(s) larger than that of the Norwegian. At 125 d after swim-up, the mean weights and coefficients of variation (CVs) in the four types of crosses were Nauyuk dam × Nauyuk sire, 2.05 g ± 20%; Nauyuk dam × Norwegian sire, 2.10 g ± 24%; Norwegian dam × Nauyuk sire, 1.91 g ± 26%; and Norwegian dam × Norwegian sire, 1.71 g ± 31%. After 125 d, the Nauyuk dam × Norwegian sire families showed superior growth, while the Norwegian dam × Nauyuk sire families grew slowly and developed large size variation. At 325 d, reciprocal effects were evident, and mean weights and CVs were Nauyuk dam × Nauyuk sire, 36 g ± 45%; Nauyuk dam × Norwegian sire, 43 g ± 48%; Norwegian dam × Nauyuk sire, 30 g ± 68%; and Norwegian dam × Norwegian sire, 38 g ± 36%. The largest individual fish in the experiment were hybrids.
Effects of Selenite and Selenate Toxicity on the Ultrastructure and Physiology of Three Species of Marine Microalgae
Authors: Wong Donald , Oliveira Luis
Published: April 2011

The main ultrastructural and physiological changes in cells of Dunaliella tertiolecta, Pavlova lutheri, and Amphidinium carterae treated with selenite or selenate involved the mitochondria and chloroplasts as well as the respiratory and photosynthetic rates. Other changes were observed in the nucleus, lipids, vacuoles, and nitrogen and carbon contents, but these showed greater variability among the microalgae studied. The major alterations suggested that energy-transducing systems were severely affected by selenium toxicity. These led to significant decreases or even elimination of storage products and major reductions in growth.
Fish Introductions in Africa and Some of Their implications
Authors: Ogutu-Ohwayo Richard , Hecky R. E.
Published: April 2011

Fish introductions in Africa have been made at various spatial scales from small fish ponds to the largest lakes, primarily to sustain or increase production, though some were to develop sport fisheries and to control unwanted organisms. Some introductions have fulfilled their objective in the short term, but several "successful" introductions have created uncertainties about their long-term sustainability. Lates niloticus, Oreochromis niloticus, O. leucostictus, Tilapia melanopleura and T. zilli were introduced into Lakes Victoria and Kyoga in 1950's and early 1960's; by the 1980's L. niloticus and O. niloticus dominated the fisheries, having virtually eliminated a number of endemic species. In Lake Victoria, the loss of genetic diversity has been accompanied by a loss of trophic diversity; the transformation of the fish community coincided with profound eutrophication (algal blooms, fish kills, hypolimnetic anoxia) which might be related to alterations of the lake's food-web structure. By contrast, the introduction of a planktivore, Limnothrissa miodon into Lake Kivu and the Kariba reservoir has established highly successful fisheries with little effect on the pre-existing fish community or trophic ecology. The endemic species-rich African Great Lakes may be particularly sensitive to introductions. Species extinctions, introgressive hybridization and ecosystem alterations may occur following introductions.
Organisation et développement du système osmorégulateur chez les Monogenea
Authors: Euzet Louis , Oliver Guy , Ktari Mohamed Hedi
Published: April 2011

On the basis of data obtained from the literature, an attempt is made to synthesize current knowledge on the oncomiracidial osmoregulatory system of the Monogenea and its evolution during post-larval development. At the oncomiracidial level, two types characteristic respectively of the Monopisthocotylea and Polyopisthocotylea are defined. In each type, many states are recognized, based on the number and disposition of protonephridia. In the Monopisthocotylea these states appear to be in harmony with the ontogenic complication of the system. The development of the osmoregulatory system of Diplectanum aequans (Wagener, 1857) is considered representative of the Monopisthocotylea. In the Polyopisthocotylea, a difference is pointed out between the post-larval development of the osmoregulatory system of the Microcotylidae and the Gastrocotylidae. The results of this synthesis add new support to the hypothesis of the polyphyletic origin of the Monopisthocotylea and the monophyletic origin of the Polyopisthocotylea.
Evaluation of characters of the digenean family Gymnophallidae Morozov, 1955
Authors: Ching Hilda Lei
Published: April 2011

Characters of the family Gymnophallidae are defined and evaluated to provide a better framework for cladistic analysis and a basis for determining its relationship with other families within the Strigeiformes. Gymnophallids are exclusively marine parasites that commonly use bivalve mollusks and rarely utilize gastropods and polychaetes as intermediate hosts. Marine birds are the final hosts, but human infections have recently been reported in Korea. Daughter sporocysts, cercarial and metacercarial germinal sacs, cercariae, and adults are stages of the life cycle. Depending on the season and species, furcocercous cercariae remain in the sporocyst or leave to find other bivalve or polychaete hosts. The metacercaria are found unencysted and in specific sites where they may cause pits in the shell, concretions, or pearls. Fossilized clams with pits are the first geological evidence of parasitism between digeneans and their hosts. Chick chorioallantoic membrane incubation of the metacercariae combined with scanning electron microscopy of adult gymnophallids can be useful in diagnostics. Seven genera of the family Gymnophallidae can be separated on the basis of 11 characters.
A new digenean, Didymocystis margolisi n.sp. (Didymozoidae: Didymozoinae), from the skipjack tuna, Katsuwonus pelamis, of Japan
Authors: Kamegai Shunya , Araki Jun
Published: April 2011

Didymocystis margolisi n.sp. (Digenea: Didymozoidae: Didymozoinae) is described from a marine fish, Katsuwonus pelamis, caught off the Pacific coast of central Japan. Worms were found in pairs in a round somewhat flattened cyst in the dorsolateral subcutaneous tissue of the host. The new species is characterized by the intestine being distended with dark ingesta from the host blood, the forebody attached near to central part of hindbody, elongated testes, and a highly branched ovary. Taxonomic problems of the genus Didymocystis and its allied genera are discussed. Didymocystis komoroensis (Nikolaeva and Dubina, 1978) n.comb. (Syn. Didymocystoides komoroensis) is proposed and the genera Coeliodidymocystoides Yamaguti, 1970 and Univitellodidymocystis Yamaguti, 1970 are considered valid.
Development of a diagnostic molecular marker forPhilonemaspp. (Nematoda; Dracunculoidea) infecting salmonids in British Columbia
Authors: Després L. , Adamson M.L. , McDonald T.E.
Published: April 2011

We developed a species specific DNA probe based on differential PCR amplification that distinguishes two congeneric nematode parasites of salmonids in British Columbia: Philonema agubernaculum Simon and Simon, 1936, usually parasitic in lake resident rainbow trout, Oncorhynchus mykiss; and P. oncorhynchi Kuitunen-Ekbaum, 1933, parasitic in anadromous sockeye salmon, O. nerka. The region differentially amplified was the D3 expansion domain of the 28S rDNA. Sequences of the two species differ in two parts of the domain, one a single base substitution and the other a three base duplication in P. oncorhynchi. A primer specific to P. oncorhynchi (amplifying P. oncorhynchi, not P. agubernaculum) was defined in the duplication region. Using differential amplification, we showed that sockeye smolts are infected with P. agubernaculum, although returning adults harbour only P. oncorhynchi. This technique could conceivably be used to quantify the frequency of heterologous infections in the wild, before infecting worms are identifiable at the species level based on morphological criteria.