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1.
A 3-D coastal ocean model with a tidal turbine module was used in this paper to study the effects of tidal energy extraction on temperature and salinity stratification and density-driven two-layer estuarine circulation. Numerical experiments with various turbine array configurations were carried out to investigate the changes in tidally averaged temperature, salinity, and velocity profiles in an idealized stratified estuary that connects to coastal water through a narrow tidal channel. The model was driven by tides, river inflow, and sea surface heat flux. To represent the realistic size of commercial tidal farms, model simulations were conducted based on a small percentage (less than 10 %) of the total number of turbines that would generate the maximum extractable energy in the system. Model results show that extraction of tidal in-stream energy will increase the vertical mixing and decrease the stratification in the estuary. Installation of in-stream tidal farm will cause a phase lag in tidal wave, which leads to large differences in tidal currents between baseline and tidal farm conditions. Extraction of tidal energy in an estuarine system has stronger impact on the tidally averaged salinity, temperature, and velocity in the surface layer than the bottom layer even though the turbine hub height is close to the bottom. Finally, model results also indicate that extraction of tidal energy weakens the two-layer estuarine circulation, especially during neap tides when tidal mixing is weakest and energy extraction is smallest.  相似文献   

2.
The present study examined actigraphically evaluated sleep on the days surrounding the greatest earthquake in Japanese history. The Great East Japan Earthquake occurred unexpectedly on the third day of a 1-week actigraphy measurement. The subjects were eight elderly (73.1 ± 4.3 years, mean ± SD) individuals living in Sendai city, one of the largest cities damaged by the earthquake. All of the subjects wore their actigraph devices until 2 days after the earthquake. The results showed that wake after sleep onset (WASO) was significantly increased (118 ± 29 min, mean ± SE) the first night after the earthquake compared with pre-earthquake values (35 ± 12 min). The subjects described being awoken by frequent aftershocks the first night. This sleep debt was recovered the next day through significant increases in daytime napping and the length of nocturnal sleep periods resulting from earlier bedtimes. An electrical blackout that lasted 2–3 days seemed to be associated with earlier bedtimes by inducing a dark and cold environment. One subject who evacuated to a school gymnasium after the earthquake suffered severely disturbed sleep due to cold temperatures (nocturnal WASO over 180 min). These findings suggest that the environmental factors related to disrupted infrastructure might have considerable impacts on sleep in the first several days after the catastrophic disaster. The findings should be considered for future disaster preparedness initiatives.  相似文献   

3.
The use of tidal currents by fishes for movements to and from onshore spawning, foraging, and nursery grounds is well documented. However, fishes’ use of the water column in tidal currents frequently exceeding 1.5 m?·?s-1 is largely unknown. With growing interest in extracting energy from the tides, understanding animal use of these dynamic environments has become essential to determining environmental effects of tidal energy devices. To assess the effects of a tidal energy device on fishes, we used down-looking single-beam hydroacoustic technology to collect pre-deployment data on the presence and vertical distribution of fishes at a pilot project site and a control site in Cobscook Bay, ME. Twenty-four-hour stationary surveys were conducted in each season of 2010 and 2011. Relative fish density and vertical distribution were analyzed for variation with respect to site, year, month, and diel and tidal cycles. A seasonal pattern in fish density was apparent in both years at both sites, with maxima in spring and late fall. Fish density was generally highest near the sea floor. Diel changes in vertical distribution were frequently observed, but changes in distribution related to tidal cycle were inconsistent. Results from the project and control sites were very similar, demonstrating that the control site provides a reference for quantifying changes in fish density and vertical distribution related to the tidal device. This approach and baseline dataset will be used to compare hydroacoustic data collected at the project and control sites after device deployment.  相似文献   

4.
Fish and decapod entry into small (1.5 m2) artificial seagrass habitats positioned on an open sand area in a New Jersey estuary was examined to determine if immigration varied between day and night. To encounter the structured habitats, colonizers had to cross an expanse of bare sand, with its presumably higher predation risk. Contrasts in abundance in the artificial seagrass plots between dawn and dusk indicated higher nighttime immigration for four species, including the fishesFundulus heteroclitus andMyoxocephalus aenaeus, and the caridean shrimpsPalaemonetes vulgaris andHippolyte pleuracanthus. Size-frequency distributions of colonizers varied between day and night for two fish species,Menidia menidia andSyngnathus fuscus, with a greater proportion of smaller individuals immigrating to the artificial seagrass at night.Callinectes sapidus also displayed a diel contrast in size distribution but, for this species, proportionately more small individuals colonized the plots during the day. We suggest that diel variability in predation risk and/or diel patterns in motor activity may be responsible for these patterns in immigration.  相似文献   

5.
This study evaluated the relative importance of the Narragansett Bay estuary (RI and MA, USA), and associated tidal rivers and coastal lagoons, as nurseries for juvenile winter flounder, Pseudopleuronectes americanus, and summer flounder, Paralichthys dentatus. Winter flounder (WF) and summer flounder (SF) abundance and growth were measured from May to October (2009–2013) and served as indicators for the use and quality of shallow-water habitats (water depth <1.5–3.0 m). These bioindicators were then analyzed with respect to physiochemical conditions to determine the mechanisms underlying intraspecific habitat selection. WF and SF abundances were greatest in late May and June (maximum monthly mean?=?4.9 and 0.55 flounder/m2 for WF and SF, respectively) and were significantly higher in the tidal rivers relative to the bay and lagoons. Habitat-related patterns in WF and SF abundance were primarily governed by their preferences for oligohaline (0.1–5 ppt) and mesohaline (6–18 ppt) waters, but also their respective avoidance of hypoxic conditions (<4 mg DO/L) and warm water temperatures (>25 °C). Flounder habitat usage was also positively related to sediment organic content, which may be due to these substrates having sufficiently high prey densities. WF growth rates (mean?=?0.25?±?0.14 mm/day) were negatively correlated with the abundance of conspecifics, whereas SF growth (mean?=?1.39?±?0.46 mm/day) was positively related to temperature and salinity. Also, contrary to expectations, flounder occupied habitats that offered no ostensible advantage in intraspecific growth rates. WF and SF exposed to low salinities in certain rivers likely experienced increased osmoregulatory costs, thereby reducing energy for somatic growth. Low-salinity habitats, however, may benefit flounder by providing refugia from predation or reduced competition with other estuarine fishes and macroinvertebrates. Examining WF and SF abundance and growth across each species’ broader geographic distribution revealed that southern New England habitats may constitute functionally significant nurseries. These results also indicated that juvenile SF have a geographic range extending further north than previously recognized.  相似文献   

6.
Fish communities in tidal tributaries have received considerable attention, but the relative value of nontidal tributaries (having a tidal amplitude of <?5 cm) may represent an under-valued habitat. A multi-gear sampling approach was used to collect fish and macroinvertebrates from one tidal and two nontidal tributaries to describe and compare the respective nekton communities and habitat use patterns. Nekton communities in tidal and nontidal tributaries were markedly different even though habitats were similar (e.g., temperature, DO, depths, shoreline vegetation). While catch-per-unit-effort (CPUE) of estuarine-dependent species (e.g., red drum, spot, common snook) was lower in nontidal tributaries, the overall nekton CPUE was twice that of the tidal tributary, and the community was comprised mostly of freshwater marsh species (e.g., eastern mosquitofish, sailfin molly, bluefin killifish). Based on the life histories of the fishes that differed between tributary types, the proximity of coastal inlets and availability of effective larval transport mechanisms for estuarine-dependent species may be greater determinants of community differences than factors related to tributary size or shoreline habitat type. These results recognize smaller nontidal tributaries as undervalued nursery habitats and suggest the function as secondary nursery habitats is a critical service to the overall estuarine community.  相似文献   

7.
We present a project management methodology designed for the selection of wind turbines wake effect most influential parameters, who need to run wind farm project for large energy conversion. Very frequently, the managers of these projects are not project management professionals, so they need guidance to have autonomy, using minimal time and documentation resources. Therefore, agile method is adapted to assist the project management. Wind energy poses challenges such as the reduction in the wind speed due to the wake effect by other turbines. If a turbine is within the area of turbulence caused by another turbine, or the area behind another turbine, the wind speed suffers a reduction and, therefore, there is a decrease in the production of electricity. In order to increase the efficiency of a wind farm, analyzing the parameters, which have influence on the wake effect, is one of the focal research areas. To maximize the power produced in a wind farm, it is important to determine and analyze the most influential factors on the wake effects or wake wind speeds since the effect has most influence on the produced power. This procedure is typically called variable selection, and it corresponds to finding a subset of the full set of recorded variables that exhibits good predictive abilities. In this study, architecture for modeling complex systems in function approximation and regression was used, based on using adaptive neuro-fuzzy inference system (ANFIS). Variable searching using the ANFIS network was performed to determine how the five parameters affect the wake wind speed. Our article answers the call for renewing the theoretical bases of wind farm project management in order to overcome the problems that stem from the application of methods based on decision-rationality norms, which bracket the complexity of action and interactions in projects.  相似文献   

8.
Community Oxygen and Nutrient Fluxes in Seagrass Beds of Florida Bay, USA   总被引：1，自引：0，他引：1  
We used clear, acrylic chambers to measure in situ community oxygen and nutrient fluxes under day and night conditions in seagrass beds at five sites across Florida Bay five times between September 1997 and March 1999. Underlying sediments are biogenic carbonate with porosities of 0.7–0.9 and with low organic content (<1.6%). The seagrass communities always removed oxygen from the water column during the night and produced oxygen during daylight, and sampling date and site significantly affected both night and daytime oxygen fluxes. Net daily average fluxes of oxygen (?4.9 to 49 mmol m?2 day?1) ranged from net autotrophy to heterotrophy across the bay and during the 18-month sampling period. However, the Rabbit Key Basin site, located in the west-central bay and covered with a dense Thalassia testudinum bed, was always autotrophic with net average oxygen production ranging from 4.8 to 49 mmol m?2 day?1. In November 1998, three of the five sites were strongly heterotrophic and oxygen production was least at Rabbit, suggesting the possibility of hypoxic conditions in fall. Average ammonium (NH4) concentrations in the water column varied widely across the bay, ranging from a mean of 6.9 μmol l?1 at Calusa in the eastern bay to a mean of 0.6 μmol l?1 at Rabbit Key for the period of study. However, average NH4 fluxes by site and date (?240 to 110 μmol m?2 h?1) were not correlated with water column concentrations and did not vary in a consistent diel, seasonal, or spatial pattern. Concentrations of dissolved organic nitrogen (DON) in the water column, averaged by site (15–25 μmol l?1), were greater than mean NH4 concentrations, and the range of day and night DON fluxes (?920 to 1,300 μmol m?2 h?1), averaged by site and date, was greater than the range of mean NH4 fluxes. Average DON fluxes did not vary consistently from day to night, seasonally or spatially. Mean silicate fluxes ranged from ?590 to 860 μmol m?2 h?1 across all sites and dates, but mean net daily fluxes were less variable and most of the time contributed small amounts of silicate to the water column. Mean concentrations of filterable reactive phosphorus (FRP) in the water column across the bay were very low (0.021–0.075 μmol l?1); but site average concentrations of dissolved organic phosphorus (DOP) were higher (0.04–0.15 μmol l?1) and showed a gradient of increasing concentration from east to west in the bay. A pronounced gradient in average surficial sediment total phosphorus (1.1–12 μmol g DW?1) along an east-to-west gradient was not reflected in fluxes of phosphorus. FRP fluxes, averaged by site and date, were low (?5.2 to 52 μmol m?2 h?1), highly variable, and did not vary consistently from day to night or across season or location. Mean DOP fluxes varied over a smaller range (?8.7 to 7.4 μmol m?2 h?1), but also showed no consistent spatial or temporal patterns. These small DOP fluxes were in sharp contrast to the predominately organic phosphorus pool in surficial sediments (site means?=?0.66–7.4 μmol g DW?1). Significant correlations of nutrient fluxes with parameters related to seagrass abundance suggest that the seagrass community may play a major role in nutrient recycling. Integrated means of net daily fluxes over the area of Florida Bay, though highly variable, suggest that seagrass communities might be a source of DOP and NH4 to Florida Bay and might remove small amounts of FRP and potentially large amounts of DON from the waters of the bay.  相似文献   

9.
Shallow water habitats within estuarine systems are believed to be important areas for small fish. While a wide variety of shallow habitats have been studied, the land that becomes inundated by the damming effect after the closure of intermittently open mouths has previously been overlooked. Fish were sampled monthly from both the main channel and flood zone of an intermittently open estuary between July 2004 and June 2005 using minifyke nets during the day and at night. A total of 7,787 fish were collected during the study representing 13 species and 11 families. Philypnodon grandiceps was the most abundant species and, together with Atherinosoma microstoma, Pseudogobius olorum, and Galaxias maculatus, made up 94% of the total catch. Inundation of the flood zone occurred in two discrete forms associated with mouth condition, which consisted of sporadic flooding while the mouth was open, to long-term flooding for 6 months after its closure. Large numbers of fish were captured on the flood zone, which included nine species; however, A. microstoma dominated the catch. A distinct shift in the flood zone fish assemblage occurred between the two mouth conditions, which is likely associated with changes in hydro-period and food availability of the flood zone and physico-chemical parameters in the main channel. There was no longitudinal variation in the fish assemblage in both the main channel and flood zone; similarly, the diel period was found to have little effect on the fish assemblage. The total catch per unit effort did not vary across seasons and suggests that fish abundance within the estuary is stable throughout the year. Unlike other estuarine systems where shallow water fish assemblages may be structured by variations in tide and elevation within the Surrey, freshwater inflow and, more importantly, mouth condition appear to have the greatest influence in composition of the shallow water flood zone fish assemblage of intermittently open estuaries.  相似文献   

10.
Inappropriate management of industrial effluents has been among major causes of water pollution and subsequent fish physiological and behavioral disorders and mortalities. This study investigated the effects of wastewater from a paper mill on immune-related gene expressions (lysozyme, tumor necrosis factor and heat shock protein 70) and hematological alterations, in juvenile rainbow trout (Oncorhynchus mykiss) during a 14-day exposure period. Following the determination of LC50, fish (135 ± 10 g body weight) were exposed to three effluent treatments: control (0), 10 and 25% of LC50, in laboratory conditions. The wastewater exposure initially increased lysozyme and tumor necrosis factor gene expression, and the expression of both genes was suppressed on the 14th day after exposure. There was a rise in heat shock protein 70 gene expression at the beginning of the experiment and then decreased to the level observed in the control group. Fish exposed to wastewater showed a significant increase in the levels of red blood cells, white blood cells and hematocrit three days following exposure, but the levels of these blood parameters significantly decreased at the end of the exposure period (P < 0.05). Our results indicated a range of immune-related gene toxicity and hematotoxicity in rainbow trout caused by the negative impacts of the industrial wastewater. Here we also discussed that poor biosecurity controls and inadequate treatments of effluents from industrial activities can lead to serious damages among wild populations.  相似文献   

11.
Predicting population- and ecosystem-level benefits of habitat restoration minimally requires an understanding of the link between the trophic ecology of a species and their use of a habitat. This study combined novel, non-lethal natural tracers of trophic ecology with acoustic tagging techniques to examine spatial and temporal patterns of habitat use of spotted seatrout Cynoscion nebulosus on Half Moon Reef (HMR), a recently restored oyster reef in Matagorda Bay, Texas. Forty-one spotted seatrout (408?±?25 mm total length) were captured at HMR, surgically implanted with acoustic transmitters, and monitored by an array of underwater listening stations from December 2015 to August 2016. Patterns of presence-absence on HMR were strongly influenced by water temperature, and to a lesser extent, salinity and tidal height. Overall, spotted seatrout residency to HMR was low, with fish being present on the reef 24% of days. When present, individual fish exhibited strong site-attachment to small portions of the reef. Residency to HMR increased significantly with size, while scale stable isotope analysis revealed fish exhibiting high residency to HMR occupied significantly smaller isotopic niches. If indeed smaller fish with decreased residency rely upon a wider range of prey items across multiple habitats than larger, more resident individuals, restored oyster reef habitat may be expected to primarily benefit larger spotted seatrout.  相似文献   

12.
Tidal fluctuation could modify the physicochemical parameters in coastal groundwater mixing zone (CGMZ) notably, which in turn largely impacts on the reactive transport, discharge, and cycling of carbon, nutrients, trace metals, and other dissolved constituents. In this study, to capture the dynamic of groundwater physicochemical parameters (e.g., salinity, dissolved oxygen, pH, temperature, and oxidation/reduction potential) under the effect of tidal fluctuation, in situ measurement of groundwater is conducted along a 2D transection at different tidal stages. The results demonstrate visible periodic variations of parameters like salinity, temperature, DO, and pH, while the groundwater pH oscillation displays a phase lag behind the tidal fluctuation. Furthermore, the salinity variation at the near-surface area is mainly controlled by the mixing process between the infiltrated seawater and groundwater. Barring the mixing process, the groundwater temperature at the near-surface area is also affected by day and night air temperature difference. Meanwhile, the depleting DO and declining pH indicate that the biodegradation via aerobic respiration is highly active in CGMZ and acts as one of the major impact factors for the DO dynamic. The sharp contrast between the high removal rate of DO (7.25 mmol m?3 day?1) and relatively low production rate of H+ (9.38 μmol m?3 day?1) demonstrates the existence of the processes consuming H+ and DO besides aerobic respiration such as dissolution of carbonates, and respiration of microorganism and mangrove roots. Moreover, owing to the mixing process, the salinity transition zone overlaps with the oxidization/reduction potential transition zone. The enrichment of Fe2+ and Mn2+ could well explain the highly reducing saline groundwater observed in this study. In a nutshell, all physicochemical parameters are sensitive to tidal fluctuation, which provides implication for further study on the variation of biogeochemical process in CGMZ.  相似文献   

13.
On Thursday, 22 of May 2014, at 6 h 22 min 0.3.3 s (GMT?+?1) a moderate-sized earthquake struck the Mostaganem, Western Algeria, region. The main shock, recorded by many international and national seismological stations, was preceded by a foreshock, 3 hours before, on May 22, 2014 (Ml?=?4.1) at 3 h 57 min 41.4 s and followed by four well-felt aftershocks (M?>?3.0) that lasted about 1 year. The main shock did not cause loss of lives but serious panic among the population was reported. The main shock, however, caused cracks in walls and roofs, sometimes destroyed, the old non-engineered and precarious adobe dweller corresponding to I0?=?VI–VII (Msk scale). We used accelerograph records to (i) determine the epicenter location (longitude?=?0.3537 E, latitude?=?35.8598 N, (ii) perform waveforms inversion to calculate the earthquake parameters. The obtained results are, respectively, the seismic moment (M0)?=?2.71 E + 16, the Mw?=?4.9 and the focal depth?=?6 km. The obtained focal mechanism solution shows reverse faulting with small right lateral component with the following nodal plans: NP1, strike?=?193.5, dip?=?49.5, slip?=?57.6 and NP2, strike?=?57.8, dip?=?50, slip?=?122.1. On the other hand, the seismotectonic framework of the Dahra area exhibits a serie of NE-SW trending “en echelon” faulted folds that may be active as suggested by this study.  相似文献   

14.
Various techniques have been used in marine fishery resources assessment. Among those, acoustic techniques have high efficiency and wide adaptability, and are environment friendly. Therefore, acoustic techniques played a key/indispensable role in the field of ecosystem-based fishery management. Acoustic surveys were conducted during the wet (May) and dry (November) seasons in 2016 in the artificial reefs ecological reserve of Bohai Gulf and a nearby control region to understand the current situation of fishery resources and explore the effectiveness of underwater artificial constructions by a dual-frequency identification sonar (DIDSON) and a scientific split-beam echosounder (120 KHz, Simrad EY60). Fish densities in various seasons and regions showed significant differences and interaction, with a maximum value of 358020.34 ind/n.mile2 in the artificial reefs’ region and a minimum value of 71898.35 ind/n.mile2 in the control region during the wet season. Fish densities in defined parallel transects revealed a roughly southward migration trend of small-size individuals from wet season to dry season. Single echo detections in the artificial reefs region demonstrated a wider target strength (TS) range (? 60 ~ ? 30 dB vs ? 60 ~ ? 51 dB) and higher mean TS values (? 55.87 dB vs ? 58.31 dB) than the control region both in the wet and dry seasons, which indicated a more complicated and stable fish community structure in the artificial reefs area. The vertical distribution of single echo detections tracked by the echoview post-processing system showed an apparent downward gathering effect. A positive correlation between TS and water depth was discovered from Pearson correlation analysis in the artificial reefs region during the dry season.  相似文献   

15.
Estuaries are highly variable environments where fish are subjected to a diverse suite of habitat features (e.g., water quality gradients, physical structure) that filter local assemblages from a broader, regional species pool. Tidal, climatological, and oceanographic phenomena drive water quality gradients and, ultimately, expose individuals to other habitat features (e.g., stationary physical or biological elements, such as bathymetry or vegetation). Relationships between fish abundances, water quality gradients, and other habitat features in the Sacramento-San Joaquin Delta were examined as a case example to learn how habitat features serve as filters to structure local assemblages in large river-dominated estuaries. Fish communities were sampled in four tidal lakes along the estuarine gradient during summer-fall 2010 and 2011 and relationships with habitat features explored using ordination and generalized linear mixed models (GLMMs). Based on ordination results, landscape-level gradients in salinity, turbidity, and elevation were associated with distinct fish assemblages among tidal lakes. Native fishes were associated with increased salinity and turbidity, and decreased elevation. Within tidal lakes, GLMM results demonstrated that submersed aquatic vegetation density was the dominant driver of individual fish species densities. Both native and non-native species were associated with submersed aquatic vegetation, although native and non-native fish populations only minimally overlapped. These results help to provide a framework for predicting fish species assemblages in novel or changing habitats as they indicate that species assemblages are driven by a combination of location within the estuarine gradient and site-specific habitat features.  相似文献   

16.
Chesapeake Bay is the largest estuary in the USA and comprises vast areas of polyhaline to freshwater, tidal fish habitat. The Bay experiences large temperature differences between winter and summer, which in combination with the variety of salinities enables approximately 240 species of fish to be temporary inhabitants. This dynamic environment leads to an ever-changing prey field for predators. The goal of this study was to characterize the diet of one of the few resident, euryhaline predators within the tidal rivers in Virginia, Lepisosteus osseus (longnose gar). The top five prey species were Morone americana, Brevoortia tyrannus, Fundulus spp., Micropogonias undulatus, and Leiostomous xanthurus. The diet composition varied with the seasonal fish assemblages, length of L. osseus, water temperature, and salinity. L. osseus consumed a greater amount of marine and anadromous fishes (%W?=?59.4 % and %N?=?56.5 %) than resident fishes (%W?=?40.6 % and %N?=?43.5 %). The seasonal influx of anadromous or coastal spawning fishes appears to be an important prey source for L. osseus and most likely other piscivores in the tributaries of Chesapeake Bay.  相似文献   

17.
Estuarine rearing has been shown to enhance within watershed biocomplexity and support growth and survival for juvenile salmon (Oncorhynchus sp.). However, less is known about how growth varies across different types of wetland habitats and what explains this variability in growth. We focused on the estuarine habitat use of Columbia River Chinook salmon (Oncorhynchus tshawytscha), which are listed under the Endangered Species Act. We employed a generalized linear model (GLM) to test three hypotheses: (1) juvenile Chinook growth was best explained by temporal factors, (2) habitat, or (3) demographic characteristics, such as stock of origin. This study examined estuarine growth rate, incorporating otolith microstructure, individual assignment to stock of origin, GIS habitat mapping, and diet composition along ~130 km of the upper Columbia River estuary. Juvenile Chinook grew on average 0.23 mm/day in the freshwater tidal estuary. When compared to other studies in the basin our growth estimates from the freshwater tidal estuary were similar to estimates in the brackish estuary, but ~4 times slower than those in the plume and upstream reservoirs. However, previous survival studies elucidated a possible tradeoff between growth and survival in the Columbia River basin. Our GLM analysis found that variation in growth was best explained by habitat and an interaction between fork length and month of capture. Juvenile Chinook salmon captured in backwater channel habitats and later in the summer (mid-summer and late summer/fall subyearlings) grew faster than salmon from other habitats and time periods. These findings present a unique example of the complexity of understanding the influences of the many processes that generate variation in growth rate for juvenile anadromous fish inhabiting estuaries.  相似文献   

18.
The introduction of a non-native freshwater fish, blue catfish Ictalurus furcatus, in tributaries of Chesapeake Bay resulted in the establishment of fisheries and in the expansion of the population into brackish habitats. Blue catfish are an invasive species in the Chesapeake Bay region, and efforts are underway to limit their impacts on native communities. Key characteristics of the population (population size, survival rates) are unknown, but such knowledge is useful in understanding the impact of blue catfish in estuarine systems. We estimated population size and survival rates of blue catfish in tidal habitats of the James River subestuary. We tagged 34,252 blue catfish during July–August 2012 and 2013; information from live recaptures (n = 1177) and dead recoveries (n = 279) were used to estimate annual survival rates and population size using Barker’s Model in a Robust Design and allowing for heterogeneity in detection probabilities. The blue catfish population in the 12-km study area was estimated to be 1.6 million fish in 2013 (95% confidence interval [CI] adjusted for overdispersion: 926,307–2,914,208 fish). Annual apparent survival rate estimates were low: 0.16 (95% CI 0.10–0.24) in 2012–2013 and 0.44 (95% CI 0.31–0.58) in 2013–2014 and represent losses from the population through mortality, permanent emigration, or both. The tagged fish included individuals that were large enough to exhibit piscivory and represented size classes that are likely to colonize estuarine habitats. The large population size that we estimated was unexpected for a freshwater fish in tidal habitats and highlights the need to effectively manage such species.  相似文献   

19.
Coastal habitat use and residency of a coastal bay by juvenile Atlantic sharpnose sharks, Rhizoprionodon terraenovae, were examined by acoustic monitoring, gillnet sampling, and conventional tag–recapture. Acoustic monitoring data were used to define the residency and movement patterns of sharks within Crooked Island Sound, Florida. Over 3 years, sharks were monitored for periods of 1–37 days, with individuals regularly moving in and out of the study site. Individual sharks were continuously present within the study site for periods of 1–35 days. Patterns of movement could not be correlated with time of day. Home range sizes were typically small (average?=?1.29 km2) and did not vary on a yearly basis. Gillnet sampling revealed that juvenile Atlantic sharpnose sharks were present in all habitat types found within Crooked Island Sound, and peaks in abundance varied depending on month within a year. Although telemetry data showed that most individuals remained within the study site for short periods of time before emigrating, conventional tag–recapture data indicates some individuals return to Crooked Island Sound after extended absences (maximum length?=?1,352 days). Although conventional shark nursery theory suggests small sharks remain in shallow coastal waters to avoid predation, juvenile Atlantic sharpnose sharks frequently exited from protected areas and appear to move through deeper waters to adjacent coastal bays and estuaries. Given the high productivity exhibited by this species, the benefit gained through a nursery that reduces predation may be limited for this species.  相似文献   

20.
Cyprinodon variegatus (sheepshead minnow), a common coastal resident of the western Atlantic Ocean and Gulf of Mexico, can live in ambient salinities ranging from 0‰ to greater than 140‰. Fish in this study were obtained from a Gulf of Mexico salt marsh near Cedar Key, Florida. This study examined the ability of individual C. variegatus to regulate plasma osmolality under the influence of a cycling salinity regime. Individuals of C. variegatus were exposed for 21 d to one of seven cyclical salinity regimes. Each cycle lasted for 2 d, with salinity varied between 10‰ and 30‰ each day. Plasma osmolality of fish from each group was determined on five dates during the course of the experiment. C. variegatus efficiently regulated plasma osmolality, even when fishes were exposed to large fluctuations in salinity. Fish previously exposed to large salinity fluctuations regulated plasma osmolality better than fish that previously had experienced no change or small changes in salinity. Increasing salinity had a greater impact on osmoregulation than did decreasing salinity.  相似文献   

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