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1.
Abstract –  We present the first data on three-spined stickleback ( Gasterosteus aculeatus ) life history and habitat use in seasonal Mediterranean streams, analysing populations from NE Iberian Peninsula. Stickleback populations were strictly annual, with reproduction events involving exclusively 1+ fish. Somatic growth was concentrated in two periods, one in spring and early summer, and another in autumn and winter. During summer there was a clear stop in the somatic growth, coupled with low values of somatic condition. This growth pattern contrasts both with that of other Mediterranean stream fish species and that of stickleback in other European locations. Stickleback populations occupied mainly intermediate locations along fluvial gradients. The presence of abundant aquatic vegetation was identified as one of the main factors related with both stickleback presence and the abundance of its populations, while the latter was also negatively related with that of invasive fish and crayfish species. Stickleback tended to occur in native-dominated fish communities, being almost absent from lower stream reaches, which bear high abundances of invasive fish species.  相似文献   

2.
In the last decades, the fish Vinciguerria lucetia (Garman) has been of important interest to the fisheries sector; nonetheless, the spawning and nursery zones in the Humboldt Current System (HCS) have not yet been defined. By using a temporal series of 23 oceanographic surveys from austral spring of 1998 to autumn 2004 off northern Chile, the spatial and temporal distribution and abundance of eggs and larvae of V. lucetia were studied. The relationships with environmental conditions (sea surface temperature, water column stratification, salinity, dissolved oxygen) were modeled using generalized additive models (GAMs). Seasonal variations in eggs and larval abundances were recorded, and higher abundances were observed in spring and summer, respectively. The main spawning areas were located at approximately between 40 and 80 nautical miles offshore. The largest abundances of V. lucetia eggs were found during spring 2003; however, larval abundances reached the highest values following the strongest ENSO event 1997–98. GAMs predicted that offshore location, sea surface temperature, and the deepening of the oxygen minimum zone, characteristics of the subtropical waters (22–24°C, >34.9, 3–6 ml/L) drove eggs and larval distributions of V. lucetia in the HCS during 1998–2004, toward areas with scarce food availability for larvae. These results suggest that spawning and larval development of this oceanic species occur in oligotrophic waters as a loophole strategy, in order to reduce predation risk during early life stages.  相似文献   

3.
Sequential ichthyoplankton surveys were used to determine the spatial and temporal distribution of eggs and larvae over coastal spawning grounds of Atlantic cod (Gadus morhua) in Smith Sound, Trinity Bay, Newfoundland, during the spring and summer of 2006 and 2007. Egg densities showed similar patterns for both years with two peaks in abundance in spring (March–April) and late summer (late July). A clear progression of development stages (1–4) was observed in spring and summer in 2006 and summer in 2007, suggesting retention of eggs within the Sound during these periods. Modelled predictions of vertical egg distributions indicated eggs were broadly distributed near the surface during spring (March–April), but were concentrated below the pycnocline (>10 m) within the inner portions of the Sound during the summer months (July–August). Back‐calculated peaks in spawning based on water temperatures were estimated at 11 and 4 April for 2006 and 2007, respectfully, with late season peaks centred on 21–24 July for both years. Environmental data indicated cooler water temperatures and periods of high wind stress in spring, and warmer, calmer periods late summer, consistent with higher retention and faster development times on the spawning grounds later in the season. We conclude that spring and summer spawning events result in different distributions of early life stages and may lead to different distributions of juvenile and adult fish.  相似文献   

4.
Between spring 1998 and autumn 1999, a fine mesh seine net was used to sample fish communities at three locations in south-eastern Australian estuaries, two located near Sydney [Botany Bay (BB) and Port Hacking (PH)] and one located approximately 150 km to the south [Sussex Inlet (SI)]. At each location, fish were collected from adjacent beds of the seagrasses Posidonia australis Hooker and Zostera capricorni Ascherson. These seagrass species differ markedly in morphology and life history. Fish communities displayed significant differences between seagrass species with respect to abundances and lengths of economically important species, and the structure of assemblages at locations in PH and BB, but not in SI. Differences appeared to be related to the recruitment of juveniles of several inshore species, such as Acanthopagrus australis (Günther), Rhabdosargus sarba (Forskaal) and Girella tricuspidata (Quoy & Gaimard) to Zostera beds at BB and PH during spring and early summer. These differences were not evident over the wider spatial scale, however, the SI location did support a distinct assemblage of fish compared with locations in PH and BB. These results suggested that local recruitment events and differences in estuarine geomorphology may be important in structuring these seagrass fish communities.  相似文献   

5.
Abstract –  Pacific lamprey, Entosphenus tridentatus , return to streams and use somatic energy to fuel maturation. Body size decreases, the lamprey mature, spawn, and then die. We predicted that warm, summer temperatures (>20 °C) would accentuate shrinkage in body size, and expedite sexual maturation and subsequent death. We compared fish reared in the laboratory at diel fluctuating temperatures of 20–24 °C (mean = 21.8 °C) with fish reared at cooler temperatures (13.6 °C). The results confirmed our predictions. Lamprey from the warm water group showed significantly greater proportional decreases in body weight following the summer temperature treatments than fish from the cool water group. A greater proportion of warm water fish sexually matured (100%) and died (97%) the following spring than cool water fish (53% sexually mature, 61% died). Females tended to mature and die earlier than males, most obviously in the warm water group.  相似文献   

6.
Abstract – Two different Denil fishways on the Grand River, Ontario, were used as check-points to evaluate the upstream movement of fishes past a low-head weir and to examine the proportions and inferred swimming performance of non-salmonid warmwater fishes that used each fishway type. Traps installed at fishway exits were used to collect fish during 24-hour sampling periods, over 40–51 days each year, from 1995 to 1997. Passage rates, size selectivity, water temperature, water velocity and turbidity for the periods of maximum passage for each year were examined. General species composition from trap samples shifted from catostomids to cyprinids to ictalurids to percids and centrarchids, with some overlap, as water temperatures increased from 8 °C to 25 °C in the spring and early summer. Water depths, and therefore water velocities in each fishway, were independent of river discharge due to variable accumulations of debris on upstream trash-racks. Relationships between the water velocity and the swimming and position-holding abilities of several species emerged. Turbidity was directly related to river discharge and precipitation events, and many species demonstrated maximum fishway use during periods of increased turbidity. This study 1) provided evidence of strongly directional upstream movements among several species that were previously considered non-migratory and 2) describes physical and hydraulic conditions during fishway use for 29 non-salmonid fish species.  相似文献   

7.
Abstract – We studied diel microhabitat use at the focal point of age‐0 bull trout, Salvelinus confluentus, in Indian Creek, Washington during mid‐summer and fall of 1997. Microhabitat variables included water depth and velocity, distance from the stream bottom, habitat and refuge use, substrate type, and substrate embeddedness. Age‐0 fish were located over fines and gravel substrates in shallow, low‐velocity water near stream margins, but were located in shallower water at night. Bull trout were highly associated with loose substrate, and used the substrate interstices for refuge cover. Diurnal bull trout counts decreased and no age‐0 fish were observed after 15 September at water temperatures below 6.1 °C. Nocturnal counts remained relatively constant throughout the study. Our results suggest that age‐0 bull trout surveys be conducted at night when summer water temperatures begin to decline.  相似文献   

8.
During summer 1997, hundreds of thousands of emaciated short-tailed shearwaters ( Puffinus tenuirostris ) died in the south-eastern Bering Sea. Using strip transect methodology, we documented the distribution and abundance of short-tailed shearwaters during cruises conducted prior to, during, and after the die-off, as well as the distributions and abundances of floating carcasses. The distributions and abundances of short-tailed shearwaters in 1997 were similar to those found during the 1970s and early 1980s. In August–September 1997, we observed 163 floating shearwater carcasses, most of which were between St Paul Island and Nunivak Island. We estimated ≈ 190 000 carcasses were afloat in the study area, about 11% of the surveyed population. Between spring (June) and autumn (August/September), mean net body mass of shearwaters decreased by 19%, mean pectoral muscle mass decreased by 14%, and mean percentage body lipid content decreased by 46%, from 15.6% in spring to 8.4% in autumn. Compared with spring, short-tailed shearwater diets broadened in autumn 1997, to include, in addition to adult euphausiids Thysanoessa raschii, juveniles of T. inermis, T. raschii and T. spinifera, crab megalops, fish and squid. We discuss how the ecosystem anomalies in the south-eastern Bering Sea during spring and summer 1997 relate to the mortality event and suggest possible implications of long-term climate change for populations of apex predators in the south-eastern Bering Sea.  相似文献   

9.
Abstract –  Factors affecting long-term variation in brown trout, Salmo trutta L., stocking success were examined in a large lake, Lake Oulujärvi, in central Finland. Brown trout were stocked in spring (late May to early June) in 1974–1991 and in summer (late June to early July) in 1992–2001. The biomass of the vendace, Coregonus albula (L.), population (prey) at release time had the largest positive effect on stocking success within both periods: biomass of adult vendace in spring and both 0+ and adult vendace in summer. Increasing the size of stocked fish had a positive effect if the vendace available at release were only adults. The increasing trend of predator-catch-per-unit-effort (CPUE) [combined CPUE of northern pike Esox lucius L., burbot Lota lota (L.), and pike-perch Stizostedion lucioperca (L.)] through the study period and its negative effect on trout stocking success suggested an increasing effect of predation within the entire time series.  相似文献   

10.
ABSTRACT:     The biomass of bighand thornyhead Sebastolobus macrochir was increased by the high recruitment success of the 1999–2002 year classes off the Pacific coast of northern Honshu, Japan. In this study, the growth of bighand thornyhead was examined over a 9-year period from 1996 to 2004 in this area. The growth of the 1999 year class and the 2000–2002 year classes was reduced at 3 and 2 years old, respectively, while the 1999–2002 year classes were smaller than the 1993–1998 year classes. In 2-, 3- and 4-year-old fish, the relationship between abundance and mean standard length was expressed by negative linear regressions, while fish became smaller when abundance of the year class was larger. Mean bottom temperatures were stable at depths of 350–900 m; variations in water temperature were small in the main distribution area of bighand thornyhead. We discuss the factors affecting the growth of bighand thornyhead via changes in the demersal fish community and feeding habits.  相似文献   

11.
Abstract –  Fishery biologists have documented small home ranges, relative to available habitat, for many littoral freshwater fishes. Home ranges for pelagic species, such as white bass Morone chrysops , are generally not well described, yet are thought to be large. We studied white bass movement using acoustic telemetry in two irrigation reservoirs of the Republican River basin in south-western Nebraska. Acoustic transmitters were implanted in fall of the previous year and tracking occurred a minimum of once per week throughout spring (mid-March to May) 2007 and 2008. Linear home ranges were calculated from observed locations of individual fish. Twelve of the twenty-seven tagged fish with at least five locations exhibited localised home ranges throughout the spring whereas the remaining fish exhibited home ranges extending across large portions of each reservoir. Home range size was not correlated with fish size or condition.  相似文献   

12.
Abstract –  Water temperatures were expected to structure river fish assemblages by promoting: (i) offspring's growth and densities in warm years, (ii) spring spawning fish when temperatures increase early and (iii) improved growth and overwintering condition from elongated vegetation periods. Favourable temperature conditions in their first year should improve growth and survival in consecutive years. In the lower Oder River, Germany, fish have been sampled annually, 0+ in July since 1997, and older fish in November since 1998. This data set was analysed to test the hypotheses mentioned above. The water temperature ranged between −0.4 and 25.1 °C during the study period, resulting in substantial variations of the 29 temperature metrics derived from daily means. Cumulative degree-days until catch, in spring and during March, as well as minimum and mean temperatures in March and spring explained 63% of the variability observed. The mean total length of the most frequent 0+ fish differed significantly between years related to temperature. Increased length growth at higher temperatures was a general tendency. Total length and density of 0+ fish were significantly inversely correlated, but the potential influence of temperature on species densities was not significant. The mean fish densities varied not significantly between years. No indication was found that higher total length in the first year of life resulted in an improved growth in subsequent years.
For future research and management it has to be expected that temperature impacts become increasingly significant in regulated river systems. With decreasing hydrodynamics the significance of temperature effects will increase.  相似文献   

13.
Pires DF, Pires AM, Collares-Pereira MJ, Magalhães MF. Variation in fish assemblages across dry-season pools in a Mediterranean stream: effects of pool morphology, physicochemical factors and spatial context. Ecology of Freshwater Fish 2010: 19: 74–86. © 2009 John Wiley & Sons A/S
Abstract –  Knowledge of patterns of refuge use by fish is critical for maintaining biodiversity in drought-prone streams. In this study, the fish assemblages of 21 dry-season pools in a Mediterranean stream were characterised and related to three sets of factors reflecting pool morphology, physicochemistry and spatial context. Fish were associated with the three sets of variables, with variation partitioning indicating that overall species richness and abundance were primarily related to pool morphology but relative species abundances were mainly associated with physicochemical contexts. In general, species richness was the highest but overall fish abundance was the lowest in large pools. Pools well shaded by riparian canopy held the highest richness and abundance of native fish, but relative species abundances and assembly structure varied among pools contingent on canopy cover, substrate composition and spatial location. These results suggested that conservation of fish diversity in Mediterranean streams requires networks of pools with diverse sizes and physicochemical contexts.  相似文献   

14.
Abstract – The objective was to compare juvenile salmon density in 20 streams throughout the very large River Tana, northern Norway, and to relate variation in density to a suite of environmental factors. Four sampling sites were electrofished in each stream (one at the mouth of the stream and three within the stream) in August and October 2000, 2001, 2002. 0+ salmon parr were absent from seven streams, present at the mouth of 11 streams, and present within only two streams, both of which were probably spawning streams. Older parr migrated upstream into most streams and their highest densities were usually found in streams flowing directly into the spawning habitat in the three largest tributaries of the Tana or the river itself. Juvenile salmon were sparse or absent in streams flowing into smaller tributaries. Most streams with high parr densities were those of dense riparian vegetation that provided terrestrial invertebrates as drift food for the salmon parr, cover for fish, cooler stream temperatures in summer, and food for benthic stream invertebrates that were also a source of food for the parr.  相似文献   

15.
Stress in freshwater fish results in an increase in serum cortisol and glucose and a decrease in serum electrolytes. These physiological indicators of stress were measured in fignerling and food-size channel catfish, "Ictalurus punctatus," before harvest, immediately after harvest, and for several days after the fish were harvested. Fingerlings were harvested in spring with either a turbine fish pump or a traditional boom-and-basket lift net. Food-size fish were harvested in winter, spring, and summer by a turbine fish pump, a vacuum fish pump, or a life net. Elctrolyte concentrations were very stable and did not show consistent effects of harvesting. Cortisol and glucose were the most sensitive to harvesting, and both increased during harvesting in all months tested. Recovery of the serum concentrations to pre-harvest levels was generally completed by the fifth day after harvest. Stress responses were similar among the different harvesting techniques, which suggests that the method of choice may be based on other factors, such as cost of available facilities.  相似文献   

16.
ABSTRACT:   Body size dependent distribution patterns of bighand thornyhead Sebastolobus macrochir were examined using bottom trawl surveys in the Tohoku area, off the Pacific coast of northern Honshu, Japan. In northern and southern Tohoku, distribution depths of ≤10-cm standard length (SL) fish increased from 500–600 m in 2003 to 600–700 m in 2005 with an increase in density of 11–20-cm SL fish at depths of 500–600 m. In 2004–2005, small fish (≤10 cm SL) were distributed in deeper waters than large fish (11–20 cm SL). In ≤20-cm SL fish, the main distribution depths changed from 300–600 m in 1997–2002 to 500–600 m in 2003 in southern Tohoku, but not in northern Tohoku. Stepwise multiple regression analysis showed that negative correlations were found in biomass densities between a few demersal fish species and bighand thornyhead at depths of 300–400 and 400–500 m in southern Tohoku. These results suggest that distribution of bighand thornyhead was affected by intra- and interspecific competitions in the Tohoku area.  相似文献   

17.
Abstract – Brook charr (Salvelinus fontinalis) is a sentinel fish species that requires clean, cold water habitats generally resulting from landscapes that allow for surface water flows devoid of sediment and contaminants and high groundwater discharge of cold water. As such, brook charr are impacted by land cover changes that alter stream temperature regimes. We evaluated brook charr populations across their eastern and midwestern range in the United States with reference to thermal habitat availability in relationship to land cover and per cent baseflow. We found that while forest cover does protect brook charr thermal habitat, high levels of groundwater discharge can allow for increased levels of agriculture within a watershed by keeping the water cold in spite of warm ambient summer temperatures. Our study concludes that with enhanced communication among land, water and fisheries managers, society can provide for sustainable stream salmonid populations despite increased threats on cold water resources.  相似文献   

18.
Abstract– Historical and contemporary fish collections were used to examine the influence of agricultural land use on fish communities in the central Chattahoochee River, USA. In-stream habitat data were also collected to examine the relationship between agricultural land use and stream habitat structure. We found a significant positive relationship between agricultural land use and in-stream sediment ( r 2=0.43, P =0.01). Stream depth heterogeneity decreased significantly with increased sediment ( r 2=0.39, P =0.02). Mainstream reaches draining agricultural lands had significantly lower levels of fish diversity than forested reaches ( r 2=0.47, P < 0.01). Agriculture also explained significant variation in mainstream species abundances but was not a significant predictor of species diversity or species abundances in headwater reaches. Most pool species that use coarse substrates decreased in relative abundance with increasing agriculture in the watershed. Our results suggest that mainstream environments and their associated communities are more susceptible than headwater reaches to the effects of agriculture. This finding has important consequences for conservation, since mainstream reaches are reported to function as species refugia during pulse disturbance events (e. g., floods, droughts).  相似文献   

19.
Fish samples collected at the cooling water intake screens of West Thurrock power station located 35.5 km downstream of London Bridge on the Thames estuary during the decade 1980–1989 were analysed. Seasonal and long-term changes in the abundance of the 15 most numerous fish species and in several fish community parameters were analysed. The majority of species were highly seasonal in their distribution and abundance. Species diversity was lower in the summer (May–August) compared with spring/winter (October–February). Evidence of long-term changes in species diversity and community structure over the decade is presented. The changes were consistent with a period of relative stability (1980–1984) followed by a period of change (1985–1989) and may reflect a deterioration in water quality in the second quinquennium. It is argued that the monitoring of fish communities in estuaries should be based on a multi-metric approach as no single indicator alone can describe the complex community structure.  相似文献   

20.
Nutritional status and feeding habits of immature female bighand thornyhead Sebastolobus macrochir were assessed based on Fulton’s condition factor K, hepatosomatic index (HSI), and stomach observations. Fish were obtained from bottom trawl samples taken seasonally during 2006/2007 in the Tohoku area, off the Pacific coast of northern Honshu, Japan. Results of the generalized linear model (GLM) indicated that fish condition deteriorated with depth, and small fish had a lower K, HSI, and percent stomach content index (SCI) than larger specimens. The empty stomach rate was higher in deeper waters in northern Tohoku (except for small fish from spring to autumn) and in southern Tohoku (spring/summer). Changes in the index of relative importance (%IRI) showed that the main prey items changed from nutritionally high to low prey items with depth. This suggests that deeper waters, where fish with the lowest condition values occur, are a poorer quality habitat for immature bighand thornyhead and that small fish are subordinate to larger fish. The effect on growth, due to variations in nutritional status and feeding habits, produced by the distributional changes in bighand thornyhead is also discussed.  相似文献   

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