bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling the temperature mediation of growth in larval fish
Authors: Bartsch Joachim 
Published: March 2003

AbstractA brief description of the logistic growth curve and its derivative is given. It is shown how to incorporate a temperature‐dependent function into this curve without changing the essential mathematical properties. This is accomplished by changing the exponential parameter in the logistic formulation from a constant value to a temperature‐dependent variable. This growth formulation is used to model mackerel (Scomber scombrus) larval growth in a Bio‐Physical Transport Model developed within the EU SEAMAR (Shelf‐Edge Advection, Mortality and Recruitment) project.
Long‐term changes in zooplankton and its relationship with squid, Todarodes pacificus, catch in Japan/East Sea
Authors: Kang Young S. , Kim Jin Y. , Kim Hak G. , Park Jong H. 
Published: March 2003

AbstractLong‐term change in zooplankton biomass and composition of major zooplankton assemblages was studied with a focus on climate change and squid catch in the Japan/East Sea. This study deals with data sets of zooplankton biomass, abundance of major zooplankton assemblages, and sea surface temperature (SST) obtained during the period from 1965 to 1998, and the catch of squid, Todarodes pacificus, from 1978 to 1998. Based on its physical characteristics, the study area was divided into two subregions, a northern and southern region.The SST during the winter and spring (February and April) steadily increased after the late 1980s in the southern region. On the other hand, the northern region did not have a warm winter and had higher interannual fluctuations. Zooplankton biomass also showed an increasing trend and major zooplankton assemblages have shifted in their composition since the early 1990s. The northern region exhibited a greater increasing trend than the southern region in zooplankton biomass. Macrozooplankton such as chaethognaths, euphausiids and amphipods gradually increased after the early 1990s. In the Japan/East Sea, squid catches increased continuously after the early 1990s. The squid catch for the autumn of year n is significantly associated with the zooplankton biomass collected in October and December of year n − 1 (r=0.864 in the northern region and r=0.818 in the southern region, P < 0.001) and macrozooplankton, especially euphausiids (r=0.578 in the northern region and r=0.840 in the southern region, P < 0.05) and amphipods (r=0.695 in the northern region and r=0.648 in the southern region, P < 0.05).
Transport of larval jack mackerel (Trachurus japonicus) estimated from trajectories of satellite‐tracked drifters and advective velocity fields obtained from sequential satellite thermal images in the eastern East China Sea
Authors: Kim Hee‐Yong , Sugimoto Takashige 
Published: March 2003

AbstractTransport processes of jack mackerel (Trachurus japonicus) larvae in the waters off the west coast of Kyushu in the eastern East China Sea, have been investigated using satellite‐tracked surface drifters and consecutive satellite thermal images. Trajectories of drifters describe northward flows over the continental shelf, eastward flows of the Kuroshio south‐west of Kyushu, and a weak clockwise gyre off the west coast of Kyushu. In particular, the clockwise gyre causes the entrainment of jack mackerel larvae into the waters off the west coast of Kyushu. Consecutive satellite thermal images help to elucidate the northward warm water intrusion from the Kuroshio front south‐west of Kyushu. Particle trajectories using sea surface current fields computed with the Maximum Cross Correlation (MCC) technique also reveal that the transport of jack mackerel larvae into the nursery ground off the west coast of Kyushu caused by the anti‐cyclonic gyre and the warm streamers are an important process for successful recruitment.
A spatially explicit study of prey–predator interactions in larval fish: assessing the influence of food and predator abundance on larval growth and survival
Authors: Pepin P. , Dower J. F. , Davidson F. J. M. 
Published: March 2003

AbstractWe apply a coupled biophysical model to reconstruct the environmental history of larval radiated shanny in Conception Bay, Newfoundland. Data on the larvae, their prey and predators were collected during a 2‐week period. Our goal was to determine whether environmentally explicit information could be used to infer the characteristics of individual larvae that are most likely to survive. Backward drift reconstruction was used to assess the influence of variations in the feeding environment on changes in the growth rates of individual larvae. Forward drift projections were used to assess the impact of predators on mortality rates as well as the cumulative density distribution of growth rates in the population of larvae in different areas of the bay. There was relatively little influence of current feeding conditions on increment widths. Patterns of selective mortality indicate that fast‐growing individuals suffered higher mortality rates, suggesting they were growing into a predator's prey field. However, the mortality rates appeared to increase with decreasing predator abundance, based on the drift reconstructions. The relationship of growth and mortality with environmental conditions suggests that short‐term, small‐scale variations in environmental history may be difficult to describe accurately in this relatively small system (∼1000 km2).
Changes in the distribution of sardine eggs and larvae off Portugal, 1985–2000
Authors: Stratoudakis Y. , Bernal M. , Borchers D. L. , Borges M. F. 
Published: March 2003

AbstractGeneralized additive models (GAMs) were fitted to sardine (Sardina pilchardus) egg distribution data from three daily egg production method surveys. The results showed that the area of egg cover off Portugal decreased significantly from 11 800 km2 in 1988 to 7000 km2 in 1997 and 7400 km2 in 1999. This is because of a significant reduction in sardine egg presence off northern Portugal, GAM estimated areas being similar or higher in the late 1990s for southwestern and southern Portugal. The distributional area covered by larvae was not estimated for 1988 (larval distribution extended beyond the survey area), although it was probably higher than the 9600 km2 for 1997 and 5500 km2 for 1999. In 1997 and 1999, the Gulf of Cadiz was also sampled, indicating extensive areas with sardine eggs and larvae (more than 50% of the total area of distribution off Portugal). Standardized data from 15 ichthyoplankton surveys between 1985 and 2000 show a decline in the mean probability of egg presence within the Portuguese continental shelf from the mid‐1980s to the late‐1990s, because of a marked reduction in egg presence off northern Portugal. Sardine larval data from the same surveys suggest that the reduction in mean probability of presence in the north is less marked than for eggs (although this comparison ignores the presence of sardine larvae beyond the continental shelf in the 1980s). Similar changes off northern Portugal and western Galicia are observed in commercial sardine catches and the acoustically estimated area of fish distribution. It is possible that the observed decline in spawning area off northwestern Iberia during the 1990s is indirectly reflecting the prevalence of environmental conditions detrimental to sardine recruitment (northerly winds during winter that favour coastal upwelling and offshore transport), which have reduced the spawning contribution of young fish in that area.
Small‐sized invertebrates in a gravel stream: community structure and variability of benthic rotifers
Authors: Schmid‐Araya J. M. 
Published: March 2003

1. The Rotifera assemblage inhabiting the streambed surface and the hyporheic zone of a gravel stream was investigated between October 1991 and October 1992. Forty‐two species of Monogononta and 27 of Bdelloidea were identified. Within these two classes, dominant species differed between the surface and the hyporheic zone. At the streambed surface, the abundance of monogonont rotifers showed a seasonal pattern with significantly higher densities in pools, whereas bdelloids showed no clear temporal trend and did not differ significantly among sites. In the hyporheic zone, the depth distribution differed among the two rotifer groups, bdelloids occurred in highest densities between 0 and 30 cm sediment depth, while monogononts were most abundant at greater depths.2. Species composition differed greatly between successive sampling dates (min. 5 to max. 26 days) at both the streambed surface and the hyporheos. At the streambed surface and in the shallow hyporheos a significantly higher percentage of species was replaced in riffles than in pools.3. Few measured hydrophysical variables were associated with the Rotifera assemblage structure. At the streambed surface, species richness was negatively correlated with water temperature and substratum heterogeneity, and Monogononta rotifer densities declined with water depth and substratum roughness.4. Permutation tests carried out on temporal serial correlations showed that, at riffle sites at the streambed surface, bdelloid rotifer densities, rotifer species richness and diversity did not differ significantly from a temporal, near‐random pattern. The hyporheic rotifer assemblage followed similar near‐random patterns.
Environmental gradients and the horizontal distribution of microcrustaceans in lakes
Authors: Smiley Elizabeth A. , Tessier Alan J. 
Published: March 2003

1. The assemblage of suspension‐feeding microcrustaceans in lakes changes along a habitat gradient from nearshore to offshore. This gradient of microcrustaceans was explored in relation to differences in macrophytes and the associated changes in water chemistry, food resources and types of predators.2. Some microcrustacean species were littoral or limnetic specialists, while others changed their distribution along this horizontal habitat gradient on a diel or seasonal basis. Distribution patterns were similar in a lake and a pond which differed in extent of macrophyte habitat.3. There was a large shift in the composition of sestonic food, indicating heterotrophic seston nearshore and more autotrophic seston offshore. Sit‐and‐wait predators of microcrustaceans (e.g. Enallagma spp.) dominated nearshore and cruising predators (e.g. Leptodora kindtii Focke) were more common offshore.4. A reciprocal transplant experiment revealed that littoral specialists could survive equally well when fed littoral or limnetic seston, while limnetic specialists performed poorly when fed littoral seston. Food resources may be important in determining where some microcrustacean species live along this horizontal habitat gradient.
Logistic regression as a tool for defining habitat requirements of two common gammarids
Authors: Peeters Edwin T. H. M. , Gardeniers And Jean J. P. 
Published: March 2003

1. Logistic regression predicts the probability of occurrence of a species as a function of environmental variables. This technique was applied to a large data set describing the distribution of two common gammarid species, Gammarus fossarum and G. pulex, in streams in the Netherlands, to evaluate its usefulness in defining habitat requirements.2. A method is presented that derives optimum habitat ranges for environmental variables from logistic regression equations. The calculated optimum habitat ranges, which are related to the maximum likelihood of presence in the field, agreed with habitat requirements and ecological tolerances in the literature.3. Single logistic regressions provide good descriptions of the optimum habitat requirements and multiple logistic regressions give insight into the relative importance of each environmental variable. It is the combination that makes logistic regression a valuable tool for constructing habitat suitability indices.4. Current velocity, pH, Kjeldahl nitrogen, total phosphorus, ammonium nitrogen, conductivity, width and depth are, in this sequence, the most important environmental variables in predicting the probability of occurrence of G. fossarum, whereas current velocity, Kjeldahl nitrogen, pH and depth are the most important variables for the prediction of the probability of occurrence of G. pulex.
The trophic interactions of young Arctic grayling (Thymallus arcticus) in an Arctic tundra stream
Authors: Golden Heidi E. , Deegan And Linda A. 
Published: March 2003

1. Young (0+) Arctic grayling (Thymallus arcticus) have the potential to control the trophic structure of Arctic tundra streams through consumption, nutrient excretion and the modification of prey behaviour. The effect of young grayling on three trophic levels (algae, invertebrates and fish) was investigated by manipulating fish density and by fertilizing the river with phosphorus (P).2. Nutrients, epilithic chlorophyll a, benthic invertebrates and fish biomass were measured within each fish density treatment (0, 4, and 40 fish m–2) within the P‐limited reference zone and the P‐enriched fertilized zone of the Kuparuk River, Alaska.3. Epilithic chlorophyll a increased with increased fish density in both reference and fertilized zones, while mayfly density decreased with increased fish density in the fertilized zone only. Final mean mass of young grayling in the 40 fish m–2 cages was lower than mean mass in the 4 fish m–2 cages.4. Young grayling may produce a top‐down cascading trophic effect in areas where nutrients are not limited.5. River nutrient status and river discharge may modify the strength of top‐down control by young grayling.
How does the vertical distribution of chlorophyll vary in littoral sediments of small lakes?
Authors: Cyr Hélène 
Published: March 2003

1. In this study, sediment chlorophyll profiles at twenty littoral stations in three oligo‐mesotrophic lakes were compared to test whether the vertical distribution of chlorophyll is related to site characteristics (light availability, temperature, physical disturbances) and whether these profiles differ between shallow and deep portions of the littoral zone.2. The magnitude of chlorophyll peaks at the sediment surface did not vary with light intensity. Chlorophyll peaks in the shallow littoral zone had a weak tendency to decrease with increasing effective fetch. The magnitude of chlorophyll peaks at deeper sites was more closely related to water temperature than to substrate slope.3. High chlorophyll concentrations were measured down to 1–3 cm in the sediments, both at shallow (< 2.5 m) and deep (4–10 m) stations. The depth to which high chlorophyll was found in sediments did not vary with effective fetch or sediment water content, two indices of wave disturbance in the shallow littoral zone, or with substrate slope, an index of sediment stability in the deep littoral zone. Sediment mixing is apparently not related to common indices of physical disturbances.4. Between 8 and 100% of sediment surface chlorophyll was ‘retained’ 4–5 cm into the sediments. The proportion of chlorophyll ‘retained’ in littoral sediments increased with increasing depth, increasing lake productivity (total phosphorus concentration) and increasing lake pH.5. Among‐core variability (standard error/mean) in chlorophyll concentration at the sediment surface ranged from less than 1% to 33% at different stations and was highest at shallow, exposed sites. These levels of variability are similar to those found in other periphytic communities.
The relationship between egg size and embryonic and larval development in the freshwater shrimp Paratya australiensis Kemp (Decapoda: Atyidae)
Authors: Hancock Marty A. 
Published: March 2003

1. Paratya australiensis egg and clutch sizes vary between lower and upper altitude sites within headwater streams of the Conondale Range, Queensland, Australia. The adaptive significance of this variation is examined by comparing the development of large eggs from upper sites with small eggs from lower sites at ambient temperatures in the laboratory.2. Embryonic duration was not dependent on egg size, but was a function of temperature (28 days at 18 °C, but only 22 days at 21 °C). However, larvae developing from large eggs were significantly larger at all stages of development, larval duration was shorter and growth rate was faster than that of larvae from small eggs.3. It is suggested that the larger, more rapidly developing larvae at upper altitude sites have a greater chance of maintaining position within headwater sections of the stream. This is important as physical barriers such as waterfalls may severely restrict upstream movement. At lower altitude sites, maintaining position may not be as critical as there are no major barriers to upstream movement following downstream displacement. The influence of temperature may also be important as larger eggs may be an adaptation to compensate for slower development of eggs and larvae at cooler, upper altitude sites. The advantage in completing larval development quickly is that larvae would have less risk of removal by spates occurring late in the breeding season.
Inhibition of phosphatase activity by dissolved humic substances and hydrolytic reactivation by natural ultraviolet light
Authors: Boavida M. ‐J. , Wetzel R. G. 
Published: March 2003

Summary1. Phosphatases released extracellularly by aquatic micro‐organisms often complex with humic compounds that are released from decomposing tissues of plants and imported in dissolved and colloidal forms to lakes and rivers.2. Dissolved humic substances from several natural sources formed complexes with phosphatases of bacterial and algal origin and reduced hydrolytic activity by non‐competitive inhibition. Restoration of the hydrolytic enzyme activities from the humic substances–enzyme complexes increased progressively over time when exposed experimentally to natural and artificial ultraviolet (UV) irradiance.3. Greater phosphatase restoration occurred from humic acid–phosphatase complexes when humic acids were extracted from dissolved organic matter (DOM) of mixed natural plant sources, than when humic acids were isolated from a decomposing single plant species.4. The data support a previously suggested hypothesis that phosphatases and other enzymes in aquatic ecosystems can complex with humic substances that dominate the DOM pool. These humic substances–enzyme complexes, in which the enzyme is temporarily inactivated, can be transported with water movements and displaced to other sites within the ecosystem. Upon exposure to UV irradiance in the photic zone, functional enzymes can be released. The potential for inactivation and storage of enzyme activity, relocation within the ecosystem, and subsequent reactivation holds important implications for regulation of nutrient cycling in fresh waters.
Effects of temperature and ultraviolet radiation on microbial foodweb structure: potential responses to global change
Authors: Rae Rowena , Vincent Warwick F. 
Published: March 2003

Summary1. A series of growth experiments were conducted with natural plankton communities from a lake and river in northern Quebec, to evaluate the response of microbial foodweb structure to changes in ambient temperature and solar ultraviolet radiation (UVR).2. Bioassays were incubated for 6 days at two temperatures (10 and 20 °C) and three near‐surface irradiance conditions [photosynthetically active radiation (PAR) + UVA + UVB, PAR + UVA, and PAR only).3. The concentration of total bacteria showed no net response to temperature, but the percentage of actively respiring bacteria, as measured with the cellular redox probe5‐cyano‐2,3‐ditolyl tetrazolium chloride (CTC), was up to 57% higher at 20 °C relative to 10 °C. Chlorophyll a concentrations in the < 2 μm size fraction also reacted strongly to temperature, with a net increase of up to 61% over the temperature range of 10–20 °C.4. The UVR effects were small or undetectable for most of the measured variables; however, the percentage of actively respiring bacteria was significantly inhibited in the presence of UVR at 20 °C, decreasing by 29–48% on day 6 in the lake experiments and by 59% on day 2 in one river experiment.5. The results show differential sensitivity to temperature among organisms of microbial communities in subarctic freshwaters, and a resilience by the majority of micro‐organisms to their present UVR conditions. Microbial foodwebs in northern freshwaters appear to be relatively unresponsive to short‐term (days) changes in UVR. However, the observed responses to temperature suggest that climate change could influence community structure, with warmer temperatures favouring picoplanktonic phototrophs and heterotrophs, and a shift in nanoplankton species composition and size structure.
Comparative energetics and life cycle of the opossum shrimp (Mysis relicta) in native and non‐native environments
Authors: Chess Dale W. , Stanford Jack A. 
Published: March 2003

Summary1. Life history, fecundity and energy ingestion were compared for non‐native Mysis relicta in Flathead Lake, Montana, and in Waterton Lake, Montana/Alberta, where the mysid is native.2. Based on estimates from stomach contents, M. relicta in Flathead Lake consumed three to four times more energy per hour while foraging than M. relicta from Waterton Lake. The primary prey of M. relicta in Flathead Lake was Daphnia thorata. Diaptomus sicilis was the primary prey for M. relicta in Waterton Lake.3. Mysis relicta in Flathead Lake had a 1‐year life history. It took 2 years for M. relicta in Waterton Lake to complete a generation. Mysis relicta from Flathead Lake produced significantly (P < 0.05) more eggs per female (19.9 ± 4.7) compared to M. relicta in Waterton Lake (13.7 ± 3.6). The lipid content in eggs from M. relicta in Flathead Lake was also significantly (P < 0.05) higher than eggs from M. relicta in Waterton Lake.4. In Flathead Lake, M. relicta is able effectively to exploit Daphnia thorata, consuming greater biomass than M. relicta in Waterton Lake. Mysis relicta efficiently assimilates the greater biomass, which reduces generation time, increases fecundity, and increases lipid reserves of offspring. These results provide evidence of energetic mechanisms that enable M. relicta to colonize and affect foodwebs when introduced into lakes.
Restoration and management of riparian ecosystems: a catchment perspective
Authors: Wissmar Robert C. , Beschta Robert L. 
Published: March 2003

Summary1. We propose that strategies for the management of riparian ecosystems should incorporate concepts of landscape ecology and contemporary principles of restoration and conservation. A detailed understanding of the temporal and spatial dynamics of the catchment landscape (e.g. changes in the connectivity and functions of channel, riparian and terrestrial components) is critical.2. This perspective is based upon previous definitions of riparian ecosystems, consideration of functional attributes at different spatial scales and retrospective analyses of anthropogenic influences on river catchments.3. Restoration strategies must derive from a concise definition of the processes to be restored and conserved, recognition of social values and commitments, quantification of ecological circumstances and the quality of background information and determination of alternatives.4. The basic components of an effective restoration project include: clear objectives (ecological and physical), baseline data and historical information (e.g. the hydrogeomorphic setting and the disturbance regime), a project design that recognizes functional attributes of biotic refugia, a comparison of plans and outcomes with reference ecosystems; a commitment to long‐term planning, implementation and monitoring and, finally, a willingness to learn from both successes and failures.5. Particularly important is a thorough understanding of past natural disturbances and human‐induced changes on riparian functions and attributes, obtained by a historical reconstruction of the catchment.