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1.
By simulating an upwelling event in a laboratory microcosm, it was possible to promote the development of a natural and diverse planktonic community. An initial bacterioplankton community which developed in response to phytoplankton growth was dominated by small coccoid forms (0,14–0,2 μm3) of the genera Vibrio and Pseudomonas. This group was heavily exploited by the heterotrophic microflagellate Pseudobodo sp. (30 μm3). Later, the bacterioplankton community was dominated by large rods (0,7 μm3) which the flagellates seemed unable to exploit. A Lotka-Volterra predator-prey model fitted to the observed data indicated that the flagellates consumed 2,4 times their carbon body mass per day or 19 bacteria·flagellate?1·h?1 when prey were not limiting. Clearance rates were inversely proportional to prey density and ingestion rate, ranging from 2 × 10?3 to 20 × 10?3) μ?·flagellate?1·h?1. At typical field densities of bacteria and heterotrophic flagellates in the southern Benguela region, between 5 and 30 percent of the water column could be cleared per day. Specific growth rates of the flagellates were positively related to prey density, the maximal rate being 0,84 · d?1. Their initially faster growth rates allowed bacteria to increase in numbers despite predation. The growth yield of the flagellates (34–36 per cent) was also positively related to food density. Such low values suggest inefficient transfer of carbon to higher trophic orders but considerable nitrogen regeneration. Nitrogen excretion rates were approximately 6–7 μg N·mg dry weight?1·h?1, comparable to other flagellates but faster than ciliates. These rates are comparable with in situ measurements of NH+4-N excretion in pycnoclinal regions based on 15N isotope studies but are only about 20 per cent of measured rates in surface waters. This is interpreted to mean that, in pycnoclinal regions where the relative input of "new" nitrogen is high, there are few regenerative steps and the model describes them satisfactorily. In surface waters, observed rates of excretion can only be accounted for by many regenerative steps in a highly complex food chain in which the cumulative total of nitrogen excretion at each step amounts to that based on 15N labelling studies.  相似文献   

2.
A mathematical model that computes the accumulation of Kepone in the striped bass food chain of the James River estuary was developed. The purpose of the model was to help understand the relationship of Kepone levels in important fish species to sediment and water column Kepone concentrations and then to address the question of why these levels still exceed Food and Drug Administration limits eight years after discharge ceased. The model considers exposure through diet and respiration at rates based on species bioenergetics. It was successfully calibrated to the Kepone concentrations observed in the period 1976 through 1982 in striped bass, white perch, and Atlantic croaker. The model indicates that for the upper levels of the food chain, diet is the major route of contamination, accounting for 87–88% of the observed concentration in croaker and white perch and 91% of the observed concentration in striped bass. The two Kepone sources; sediment and water column, contribute approximately equally to the croaker and white perch. The water column is more significant for striped bass, being the original source for approximately 60% of the observed body burdens. It was estimated that a criterion requiring Kepone concentrations in fish to be at or below 0·3 μg g?1 would require dissolved water column and sediment Kepone concentrations to be reduced to somewhere between 3 and 9 ng l?1 and 13–39 ng g?1, respectively, depending on the species. Striped bass require the greatest reductions in dissolved water column and sediment Kepone concentrations to somewhere between 3 and 5 ng l?1 and 13 and 24 ng g?1, respectively.  相似文献   

3.
Between 1966 and 1989,255 shortfin mako sharks Isurus oxyrinchus were caught in the gill nets which protect the tourist beaches of Natal. The catch rate showed no trend, fluctuating about a mean of 0,34 sharks·km-net?1·year?1. Catches were highest between May and November, when the water tends to be cooler. The sex ratio was 1,4 males to 1 female. Specimens ranged in size from 84 to 276 cm precaudal length, with a mode of 191–195 cm for males and 251–255 cm for females. Males matured at 160-170 cm and females at approximately 220 cm. Catches included two recently fertilized females and two with well-developed embryos. External injuries were found on 14 per cent of males examined and 41 per cent of females. Elasmobranchs were the most common prey category, occurring in 60 per cent of stomachs containing food, followed by teleosts at 40 per cent. Most of the elasmobranch prey were sharks shorter than 1 m.  相似文献   

4.
Anchovy biomass and copepod standing stocks and growth rates on the Agulhas Bank were compared during the peak spawning period (November) in 1988 and 1989. In 1988, copepod biomass over the western Agulhas Bank was low (1,0 g dry mass·m?2) relative to anchovy biomass there (14,7 g dry mass·m?2). In November 1989 in the same area, fish biomass was much lower (5,7 g dry mass·m?2), following a recruitment failure, and copepod biomass was higher (2,4 g dry mass·m?2), possibly as a result of lesser predation by anchovy. By contrast, the eastern Agulhas Bank had a larger biomass of copepods (4–6 g dry mass·?2) and a lower biomass of anchovy during both years. Knowing, from laboratory studies, that a prey biomass of 0,78 g·m?2 is required for fish to obtain their daily maintenance ration, it is suggested that spawning on the western Agulhas Bank was food-limited in 1988. Copepods on the western Bank may be replaced by local growth or transport from the eastern Bank. Growth rates of copepods on the western Bank were 10–50 per cent of maximum in 1988, but total production (c. 100 mg dry mass·m?2·day?1) was low, primarily because biomass was low and less than the rate of consumption by anchovy (243 mg copepod dry mass·m?2·day?1). On the eastern Bank, copepod production exceeded anchovy consumption and it is concluded that the flux of copepod biomass onto the western Bank may be as important as local growth in replenishing copepod stocks there. Feeding conditions for anchovy on the western Agulhas Bank are often marginal compared to the situation on the eastern Bank, and it is suggested that the selection of the western Bank as the major spawning area is related more to the success of transport and survival of eggs and larvae on the West Coast recruiting grounds than to feeding conditions per se.  相似文献   

5.
《Oceanologica Acta》2003,26(5-6):503-509
The first evaluations of the daily ration and population food consumption of four Sciaenid fish, under natural conditions for the Brazilian south-western Atlantic shelf (23°35′S, 45°00′W) are presented. The average daily ration ranged from 4.38 to 12.92 % body mass (90% confidence interval) for the juvenile shortfin corvina (Isopisthus parvipinnis), from 0.41 to 5.52 % body mass (90% confidence interval) for the juvenile shorthead drum (Larimus breviceps) and from 3.14% to 3.15% body mass for the juvenile whitemouth croacker (Micropogonias furnieri). Juveniles of the banded croacker (Paralonchurus brasiliensis) showed higher estimates (2.58–2.60% body mass) than those for the adults (1.2–1.84% body mass). The mean food consumption rate of the population was estimated at about 11 and 8 year–1, respectively, for the whitemouth croacker, and banded croacker, corresponding to a gross efficiency of 13 and 10%. The estimates of daily ration were related to the feeding habits as well as to size of the fish, and probably to their specific energy budget. Estimates of population food consumption are related to population structure.  相似文献   

6.
The Cape rock lobster Jasus lalandii is a major predator in the inshore Benguela system. The mean density and biomass at Oudekraal is 0,48 individuals ·m?2 or 49,75 g dry mass ·m?2. The main component of its diet is Aulacomya ater, the ribbed mussel, which has a mean biomass of 1,15 kg dry mass ·m?2. Daily consumption of carbon and nitrogen from this source reaches a maximum in summer and, when J. lalandii feed on mussels, 14,1 per cent of the flesh is lost to the environment as a result of "messy feeding". The absorption efficiency of ingested nitrogen is 86,2 per cent. Ammonia and urea excreted in the first 12 h after feeding represent 6,7 and 1,6 per cent respectively of the nitrogen ingested. Endogenous nitrogen excretion has a mean rate of 1,9 μg N·g (dry mass)?1·h?1 The range of estimates for combined figures of kelp and phytoplankton nitrogen requirements are 76,4 – 86,7 g N·m?2·year?1 J. lalandii returns 6,3 g N·m?2·year?1 to the system, accounting for 7,2 – 8,2 per cent of annual kelp and phytoplankton requirements. This could be of particular importance during downwelling when the supply of new nitrogen is limited.  相似文献   

7.
Drift was collected over 24‐h periods in five rivers in South Island, New Zealand, to determine whether diel periodicity was consistent across a range of river types, and whether the pattern was similar for different life stages/sizes of selected taxa. Total drift density (numbers per 100 m3 ) of aquatic invertebrates was greater at night than during the day in all rivers; peak abundance occurred shortly after sunset in clear water rivers and shortly before sunrise in a turbid, glacier‐fed river. Densities of drifting Deleatidium spp., Nesameletus spp. (both Ephemeroptera), Aoteapsyche spp., and Hydrobiosidae (both Trichoptera), were generally greater at night than during the day. However, the timing of peak abundance in the drift for other common taxa varied between rivers. Larger Deleatidium spp. larvae (> 1.00 mm head width) were more common in the drift at night than during the day in all rivers. However, this was not apparent for Aoteapsyche spp. and Hydrobiosidae, for which diel differences in the size of drifting animals were not consistent even within the same river. The propensity for some aquatic invertebrates to drift at night may influence fish feeding behaviour, particularly with respect to the timing of feeding and the species or life history stages of their prey.  相似文献   

8.
Ichthyoplankton and microzooplankton were collected twice monthly for one year at a single station in Biscayne Bay, Florida. Based on approximate 10-m3, 333-μm mesh bongo net samples, the mean annual densities were 17·7 m?3 and 1·8 m?3 for fish eggs and larvae, respectively. Ichthyoplankton was most abundant in spring-summer. The most common fish larvae were bay anchovy (Anchoa mitchilli), spotted dragonet (Callionymus pauciradiatus), thread herring (Opisthonema oglinum) and gobies (Gobiidae), which comprised 50% of all larvae collected. A comparison of 35-μm and 333-μm mesh, bongo net collections revealed that mean densities of fish larvae were 8·5 times higher in the smaller mesh. The most abundant microzooplankton, based on 35-μm bongo net collections, were copepod nauplii, <100 μm in width, which averaged 90·41?1 and tintinnids which averaged 168·51?1. The mean density of microzooplankton <100 μm wide, potentially suitable food for first-feeding fish larvae, was 104·91?1, exclusive of tintinnids, and 273·41?1 including tintinninds. Excepting tintinnids, seasonal variability in microzooplankton abundance was low relative to that for ichthyoplankton. High microzooplankton densities, combined with low seasonal variability, indicated that feeding conditions for fish larvae were usually good in Biscayne Bay. Copepods, especially nauplii, were the predominant food of fish larvae (71% of all food items). Only mollusc veliger larvae (18% of all food items) were highly preferred prey but they were a small component of most larval fish diets. Average width of prey eaten by first-feeding larvae was 74 μm. Prey size increased in relation to larval length.  相似文献   

9.
Feeding periodicity, consumption rate, absorption efficiency, respiration rate and ammonia excretion were measured as functions of wet body mass in abalone collected from the western and southern Cape coasts. A well developed diel feeding rhythm was evident, consumption being restricted to the period 16h00–08h00. Food intake averaged 8,1 per cent of wet flesh mass·d?1 at 14°C and 11,4 percent at 19°C. The daily consumption rate was related to body mass by the relationships C(g) = 0,54 W(g)0,67 at 14°C and C(g) = 0,35 W(g)0,77 at 19°C. Absorption efficiency averaged 37 per cent and was independent of body size. Equations relating respiration rate to wet body mass were R(m? O2·h?1) = 0,03 W(g)0,83 at 14°C and R = 0,03 W(g)0,94 at 19°C. No significant differences were detected between day and night rates or between fed and starved individuals. The rate of ammonia excretion (μmole·h?1) was related to wet body mass (g) by the equations U = 0,22 W0,43 at 14°C and U = 0,03 W0,85 at 19°C.  相似文献   

10.
Diel changes in vertical distribution and gut pigment contents of Acartia clausi andPseudodiaptomus hessei were studied during several 24-h time series performed between 1993 and 1997 in four sites of the Ebrié Lagoon (Côte d'Ivoire). The sites differed by their morphology and their hydrological structure and by the vertical distribution of chlorophyll biomass. Both species showed classical diel vertical migrations (DVM). Copepodites and adult stages of P. hessei were almost benthic during the day and evenly distributed through the water column at night. The amplitude of DVM of A. clausi increased from copepodites I–III to adults. Copepodites and adults of A. clausi increased significantly their gut fluorescence at night, whereas those of P. hessei showed no clear diel feeding rhythm (DFR). These results suggest that A. clausi feed mostly at night on phytoplanktonic particles and P. hessei feed mostly on benthic algal particles during the day and on sestonic particles at night. No relationship was observed between DFR and DVM because both patterns occurred when food was either vertically homogeneous or vertically stratified. The daily average gut fluorescence of A. clausi increased with ambient chlorophyll concentration until around 12–15 μg l−1, whereas no relationship was found for P. hessei. The implication of these patterns on the adaptation capacities and the behaviour of the two species are discussed. The DVM of P. hessei should explain its rarity in the estuarine area. The comparison of our results with previous ones suggests an evolution of A. clausi DFR between 1981–1982 and 1996–1997, in relation to an intensification of eutrophication.  相似文献   

11.
Knowledge of the nutritional conditions of coastal commercial fish populations is key to understanding stock health status, and is essential when making reasonable exploitation and management plans. Here, we present the first results on the condition and feeding preferences of two coastal fish species, Diplodus sargus (Linnaeus, 1758) and Pagellus erythrinus (Linnaeus, 1758). Using stable isotope and biochemical analyses, we tested the potential effects of a marine protected area (MPA) and the occurrence of a dramatic coastal storm on the condition and quality of nutrition. The results suggest that both condition (lipids) and nutrition quality (fatty acids, FAs) in P. erythrinus and D. sargus depend upon on food availability in the area in which they were captured. Pagellus erythrinus individuals inside the MPA stored higher quantities of lipids [46.73 ± 19.00 μg lipid·mg organic matter (OM)?1] than those outside the MPA (15.63 ± 5.30 μg lipid·mg OM?1) only before the storm. Diplodus sargus showed different FA signatures inside and outside the MPA before and after the storm. These results suggest that D. sargus increased their quality of nutrition inside (16.62 ± 3.17 μg FA·mg OM?1) versus outside (7.88 ± 2.36 μg FA·mg OM?1) the MPA, owing to increased food diversity and availability. Conversely, P. erythrinus did not show differences in nutritional quality inside (18.12 ± 1.13 μg FA·mg OM?1) or outside (18.81 ± 1.42 μg FA·mg OM?1) the MPA, possibly because of the increase in ingestion not affecting the studied parameters. In P. erythrinus, the FA concentration decreased after the storm, but in D. sargus, a change in lipid composition was observed. These results suggest that P. erythrinus appears to be more impacted by food quality (different saturated and unsaturated FAs) than D. sargus, owing to a more restrictive diet. We hypothesize that the observed differences between inside and outside the MPA are not only related to the degree of protection, but also to the feeding preferences and behaviour of both fishes.  相似文献   

12.
Numerical data based on stomach content analysis of the zooplanktivorous freshwater fish, Retropinna semoni, were used to examine the effect of fish sample size on mean counts of dominant prey items. Fifty adult R. semoni were collected from throughout the open‐water of Lake Benanee, Australia at each of five times over a diel period. Bootstrapping was used to generate confidence intervals around sample means, and markedly more accurate means were obtained from samples collected in the day than the night. High variation in night samples was the by‐product of a diurnal feeding regime. Traditional sample sizes of 10 to 15 stomachs resulted in reasonable confidence intervals of sample means derived from collections on the first day, corresponding to uniform feeding patterns in the population. However, increased sample sizes were required to describe more complex feeding behaviour on the second day, when a proportion of the population switched to an alternative prey source.  相似文献   

13.
Torrentfish Cheimarrichthys fosteri Haast were collected at 4‐hour intervals over a full day in winter and summer, 1984–85, from the Ashley and Rakaia Rivers in Canterbury, New Zealand, to determine their diel feeding periodicity. Both populations fed, almost exclusively, from dusk to dawn in both seasons, with the quantity of food in their stomachs accumulating to peak levels by early morning. However, Ashley females had significantly less food in their stomachs than did males in summer, the season with a high incidence (91%) of females in spawning condition. Aquatic stages of Deleatidium spp. (Ephemeroptera: Leptophle‐biidae) and Chironomidae constituted from 85 to 98% by number and 63 to 80% by dry weight of all foods eaten. Chironomids (small prey) comprised up to 85% of the total foods eaten by number but only 17% by dry weight, while Deleatidium (large prey) comprised up to 69% of the prey by number and 63% by dry weight. Numerically, chironomids were an important component in the torrentfish diet in both seasons in the Rakaia (71 to 75%), but only so in winter in the Ashley (85%). The reported daily feeding cycle is consistent with observations in a simulated stream, that torrentfish largely remain inactive during the day and come out to feed at night.  相似文献   

14.
Mesopelagic fishes represent an important component of the marine food web due to their global distributions, high abundances and ability to transport organic material throughout a large part of the water column. This study combined stable isotope (SIAs) and gut content analyses (GCAs) to characterize the trophic structure of mesopelagic fishes in the North‐Central Gulf of Mexico. Additionally, this study examined whether mesopelagic fishes utilized chemosynthetic energy from cold seeps. Specimens were collected (9–25 August 2007) over three deep (>1,000 m) cold seeps at discrete depths (surface to 1,503 m) over the diurnal cycle. GCA classified 31 species (five families) of mesopelagic fishes into five feeding guilds: piscivores, large crustacean consumers, copepod consumers, generalists and mixed zooplanktivores. However, these guilds were less clearly defined based on stable isotope mixing model (MixSIAR) results, suggesting diets may be more mixed over longer time periods (weeks–months) and across co‐occurring species. Copepods were likely important for the majority of mesopelagic fishes, consistent with GCA (this study) and previous literature. MixSIAR results also identified non‐crustacean prey items, including salps and pteropods, as potentially important prey items for mesopelagic fishes, including those fishes not analysed in GCA (Sternoptyx spp. and Melamphaidae). Salps and other soft‐bodied species are often missed in GCAs. Mesopelagic fishes had δ13C results consistent with particulate organic matter serving as the baseline organic carbon source, fueling up to three trophic levels. Fishes that undergo diel vertical migration were depleted in 15N relative to weak migrators, consistent with depth‐specific isotope trends in sources and consumers, and assimilation of 15N‐depleted organic matter in surface waters. Linear correlations between fish size and δ15N values suggested ontogenetic changes in fish diets for several species. While there was no direct measure of mesopelagic fishes assimilating chemosynthetic material, detection of infrequent consumption of this food resource may be hindered by the assimilation of isotopically enriched photosynthetic organic matter. By utilizing multiple dietary metrics (e.g. GCA, δ13C, δ15N, MixSIAR), this study better defined the trophic structure of mesopelagic fishes and allowed for insights on feeding, ultimately providing useful baseline information from which to track mesopelagic trophodynamics over time and space.  相似文献   

15.
The Gross growth efficiency(GGE) is defined as the amount of consumer carbon produced relative to the amount of prey ingested in a given time interval. In population ecology, it can be considered as an index for the ability of a consumer to convert the biomass of food into its population production. In this study, it was firstly applied to estimate the role of amphipods grazing in the biomass dynamics of macroalgae(Ulva lactuca) in Yundang Lagoon(a subtropical eutrophic coastal lagoon, Xiamen City, China). It was found that amphipods were the dominant group(82.2%–98.7%) in the benthic assemblage, in which five amphipod species(Corophium uenoi, Ampithoe valida, Grandidierella japonica, Grammaropsis laevipalmata and Caprella panantis) were observed in the lagoon. However, only A. valida significantly consumed U. lactuca among these amphipod species. A series of experiments were conducted to estimate the consumption of U. lactuca by A. valida. It was suggested that the monthly secondary production(P) of A. valida using size frequency method ranged from 2.39 to 13.68 g/m2. GGE of A. valida exponentially reduced with body size and was closely associated with water temperature. Therefore, GGE equation for different months using the temperature recorded during the field investigation was fitted. The monthly consumption of U. lactuca was figured out to be 86.7–1 549.0 g/m2 by the sum of consumption(P/GGE) by A. valida at different size, accounting for 2.0%–37.5% of U. lactuca production. It indicates that the grazing effect of A. valida did play a role in reducing the accumulation of U. lactuca biomass when A. valida was abundant, but it finally fails to limit the U. lactuca growth in Yundang Lagoon. Low abundance of A. valida and high nutrient loading may be two major reasons for the outbreak of U. lactuca bloom in the lagoon.  相似文献   

16.
The feeding behaviour of adults of the marine calanoid copepod Centropages hamatus was studied in laboratory experiments with ciliates and phytoplankton as food sources. The ingestion rate of algal (flagellates, diatoms) and ciliate prey (oligotrichs) as a function of prey concentration could be described by a Holling type III functional response, with close to zero ingestion rates at concentrations below 5 µg C l− 1. In general, ingestion of ciliates was higher than ingestion of algae, and maximum feeding rates by adult males reached were half the feeding rates of adult females at prey concentrations exceeding 50 µg C l− 1. When diatoms and ciliates were offered together C. hamatus (both sexes) fed exclusively on ciliates as long as they contributed with more than 5% to the mixture. This indicates the capability of active prey selection and switching between suspension feeding and ambush predation. Therefore, the feeding behaviour of adult C. hamatus can be characterised as omnivorous with a preference for larger motile prey. This implies a trophic level above two, if there is a sufficient abundance of protozoan food available.  相似文献   

17.
Abstract

Stomach contents of Gobiomorphus cotidianus,Retropinna retropinna, Gambusia affinis, and Anguilla australis were compared between two shallow lakes in the lower Waikato River basin, to examine the relationship between turbidity and diet. Lake Waahi and the south arm of Lake Whangape had been turbid (20–40 g suspended solids (SS) m?3) and devoid of submerged macrophytes since the late 1970s and early 1980s, respectively. The main basin of Lake Whangape had been generally clearer (5 g SS m?3) with dense beds of submerged macrophytes, but at the time of sampling (1987) water clarity had deteriorated (> c. 10 g SS m3) and submerged macrophytes had declined. The mysid Tenagomysis chiltoni was an important prey for all species of fish from turbid water bodies but was less important in stomachs of fish in the main basin of Lake Whangape. Apparently, mysids were not an important prey in Lake Waahi before it became turbid. Chironomid larvae and pupae dominated the diets of small fish in the main basin of Lake Whangape. Fish and mysids were the most important prey of shortfinned eels in both lakes, with mysids most important in Lake Waahi. High mysid densities in the turbid water bodies provide an alternative food resource apparently compensating for those lost by fish when water clarity declined and submerged macrophytes collapsed.  相似文献   

18.
The Peruvian anchovy or anchoveta (Engraulis ringens) forages on plankton and is a main prey for marine mammals, seabirds, fish, and fishers, and is therefore a key element of the food web in the Humboldt Current system (HCS). Here, we present results from the analysis of 21,203 anchoveta stomach contents sampled during 23 acoustic surveys over the period 1996–2003. Prey items were identified to the genus level, and the relative dietary importance of different prey was assessed by determination of their carbon content. Variability in stomach fullness was examined relative to the diel cycle, the distance from the coast, sea surface temperature, and latitude, using generalized additive models (GAMs). Whereas phytoplankton largely dominated anchoveta diets in terms of numerical abundance and comprised >99% of ingested prey items, the carbon content of prey items indicated that zooplankton was by far the most important dietary component, with euphausiids contributing 67.5% of dietary carbon followed by copepods (26.3%). Stomach fullness data showed that anchoveta feed mainly during daytime between 07h00 and 18h00, although night-time feeding also made a substantial contribution to total food consumption. Stomach fullness also varied with latitude, distance from the coast, and temperature, but with substantial variability indicating a high degree of plasticity in anchoveta feeding behaviour. The results suggest an ecological role for anchoveta that challenges current understanding of its position in the foodweb, the functioning of the HCS, and trophic models of the HCS.  相似文献   

19.
本研究根据2011年及2013—2016年春季和秋季在海州湾及其邻近海域进行的底拖网调查数据，结合同步采集的底层海水温度、底层海水盐度、水深、底质类型，以及脊腹褐虾(Crangon affinis)、细螯虾(Leptochela gracilis)、鳀(Engraulis japonicus)、赤鼻棱鳀(Thrissa kammalensis)等小黄鱼(Larimichthys polyactis)主要饵料生物的资源丰度数据，采用条件数κ和方差膨胀因子(VIF)度量多重共线性的程度，选取关键环境因子，再应用基于Tweedie分布的广义可加模型(GAM)研究不同季节和不同生长阶段的小黄鱼资源丰度与环境因子的关系。多重共线性的检验表明，所有初始变量之间没有显著的多重共线性，均可作为解释变量代入模型。结果表明:不同季节和生长阶段，影响小黄鱼资源分布的主要因子及其偏差解释率各不相同，各变量所对应的适宜范围也不同。例如:影响春季小黄鱼幼体资源分布的主要因子有底层海水温度、底层海水盐度、水深和脊腹褐虾的分布，其中偏差解释率最大的因子为水深(16.09%)；而影响春季成体资源分布的因子为底层海水温度、底层海水盐度、水深及脊腹褐虾和鳀的分布，其中偏差解释率最大的因子为底层海水盐度(13.56%)。本研究表明，海州湾及其邻近海域不同季节和不同生长阶段小黄鱼的资源分布与其自身的生态习性、海洋环境以及饵料生物的分布密切相关。  相似文献   

20.
The present study provides the first estimate of the daily ration for a goby species in the Mediterranean Sea, using a new approach to determine the mass of fish stomach contents through the sum of individual prey dry mass derived indirectly from prey size. Diel feeding activity and daily ration of the pelagic goby Aphia minuta were studied under natural conditions in the coastal waters off Comacchio (Northwestern Adriatic Sea) during the spring season. A total of 318 individuals of A. minuta, collected by 14 trawls carried out on 4 consecutive days, was examined for gut contents. The diel pattern of the vacuity index and the stomach fullness index indicated that A. minuta has nocturnal feeding behaviour. The daily ration, computed over a period of 16 h, was equivalent to 2.23% wet body mass.  相似文献   

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