拟目乌贼幼体日摄食量及其对体重影响

在人工养殖条件下,对拟目乌贼幼体的日摄食量和日增重率进行了分析。结果显示,在水温、盐度、pH等条件相对稳定的环境下,10～15d的拟目乌贼幼体平均日摄食虾苗(体长0.5mm)的条数分别是8、11、12、13、78、83条,在这种摄食量下,拟目乌贼幼体的日增重率分别为6.8%、5.68%、6.44%、8.81%、12.5%。其胴长、体重的生长符合S型曲线生长规律。     

布氏田鼠摄食量、累积摄食量与日龄的关系

布氏田鼠 (Ｍｉｃｒｏｔｕｓｂｒａｎｄｔｉ)是内蒙古典型草原区的主要害鼠 ,其危害方式主要表现之一为与牲畜争夺牧草资源[1,4 ,11,12 ] 。准确地测定其日食量(ＤＦＣ)与累积摄食量 (ＣＦＣ) ,对于定量地衡量该鼠的危害程度 ,进一步推算鼠害防治的经济阈值有着重要的意义。一些学者着手有关该鼠食性与食量 ,以及非取食性牧草消耗量的研究工作[3 ,7～ 9] 。但由于受实验手段的限制 ,一直未能解决布氏田鼠日食量、累积摄食量与田鼠年龄的关系等难题。本文以测定典型草原区布氏田鼠日食量与体重的关系 ,结合布氏田鼠体重与年龄的数学关系方程 …     

The Microbial Food Web in Eutrophic Shallow Estuaries of the Baltic Sea

Microbial food webs are responsible for the main carbon flow in shallow eutrophic estuaries of the Baltic Sea. Bacteria account for respirative use most of the autotrophic production. Bottom-up influences are mainly directed to the phytoplankton. Massive increase of phytoplankton biomass has only little effect on the biomasses of the heterotrophic plankton. The investigated ecosystem obviously differs by its high bacteria/non-bacteria heterotrophs-relation from other aquatic ecosystems.     

Estimation of the Consumption of Nekton and Plankton by the Minke Whale Balaenoptera acutorostrata

This is a review of the data available on the population subdivision and life cycle of the Minke whale, the most abundant whalebone whale in the World Ocean. Different methods of estimation and calculation of the rate of food consumption by this species, the latter including those developed for the Sea of Okhotsk, are compared.     

Annual Changes of Abundance and Biomass of Planktonic Ciliates in the Gdańsk Basin,Southern Baltic

Seasonal changes in the species composition, abundance and biomass of planktonic ciliates were determined every 2–3 weeks at two sites of 30 m depth and one location of 105 m depth in the southwestern Gdańsk Basin between January 1987 and January 1988. A total of 40 ciliate taxa were observed during this period. Autotrophic Mesodinium rubrum dominated ciliate abundance and biomass: maximal values of 50 · 10⁻¹ ind. ^1-1 and 65 μg C 1⁻¹ were recorded. The annual mean biomass of M. rubrum comprised 6 to 9% of the annual mean phytoplankton biomass. The highest abundances and biomasses of heterotrophic ciliates were noted at all stations in the spring and summer in the euphotic zone with maximum values of 28 · 10³ ind. 1⁻¹ and 23 μg C 1⁻¹. Three ciliates assemblages were distinguished in the epipelagic layer: large and medium-size non-predatory ciliates, achieving peak abundance in spring and autumn; small-size microphagous ciliates and epibiotic ciliates which were abundant in summer, and large-size predacious ciliates dominating in spring. Below 60 m, a separate deep-water ciliate community composed of Prorodon-like ciliates and Metacystis spp. was found. The ciliate biomass in the 60–105 m layer was similar to the ciliate biomass in the euphotic zone. The heterotrophic ciliate community contributed 10 to 13% to the annual mean zooplankton biomass. The potential annual production of M. rubrum comprised 6 to 9% of the total primary production. Carbon demand of non-predatory ciliates, calculated on the basis of their potential production, was estimated to be equivalent to 12–15% of the gross primary production.     

On the Importance of Planktonic Protozoans in the Eutrophication Process of the Baltic Sea

Analysing the results of various authors recent studies in the pelagic region of the Baltic revealed that protozoan biomass is in the same range or even higher than metazooplankton biomass. The dominant groups of planktonic protozoans are heterotrophic pico- and nanoflagellates (various taxonomic groups), large heterotrophic flagellates (mainly dinoflagellates) and ciliates. Regularly the spring bloom of phytoplankton is accompanied by a maximum of protozoan biomass which declines in early summer as a result of intensive grazing pressure by metazooplankton and changing food conditions. The analysis of results from different stations indicated that biomasses of protozoans increase with an increasing degree of eutrophication. Several trophic levels within the microbial web should be added to the traditional view on the pelagic food web of the Baltic. Our knowledge regarding the quantitative aspect of the microbial matter flux of the Baltic is very limited up to now and complex ecological (and taxonomical) studies using standardized methods including all protozoan components are necessary. Protozoans (various trophic groups and levels), besides bacteria, should be viewed as the metabolically most active heterotrophic component in the pelagic region of the Baltic, their activity should increase with an increasing degree of eutrophication.     

Consumption and gut evacuation rate of laboratory‐reared spotted seatrout (Sciaenidae) larvae and juveniles

The temperature and mass dependence of maximum consumption rate was measured for larval and early juvenile spotted seatrout Cynoscion nebulosus . Maximum consumption ( C _MAX) estimates were obtained from feeding and gut evacuation experiments on larvae (3·8–19 mm standard length, L _S) at three temperatures (24, 28 and 32° C), and maximum consumption experiments on juveniles at three temperatures (20, 26 and 32° C). Feeding levels were determined for larvae fed live prey ( Brachionus plicatilis and Artemia salina ) ad libitum . The midgut and total evacuation times were estimated for fish feeding continuously and discontinuously using alternate meals of tagged and untagged live prey. Temperature and fish size had significant effects on gut evacuation and consumption. The gut evacuation time increased with increasing fish size, and decreased with increasing temperatures. Mass‐specific midgut contents increased for small larvae <0·156 mg dry mass ( M _D)( c . 4 mm L _S), and decreased for larger larvae and juveniles. Maximum consumption was modelled by fitting a polynomial function to a reduced dataset of individuals feeding at high levels. The C _MAX model predicted an initial increase in specific feeding rate from 70 to 155% M _D day⁻¹ for small larvae, before declining for larger larvae and juveniles.     

New Approaches to Mesozooplankton Production Estimates against the Background of Food Web Considerations for the Bornholm Basin (Southern Baltic Proper)

Mesozooplankton production was estimated by using a new sampling technique and two alternative calculation methods. In essence, production estimates are based on significantly higher abundances. The contribution of juvenile stages to copepod and fish dynamics was generally low, so that the omission of juvenile stages in budgets will result in a small error. The situations reported in this study present a unique food web szenario, which in detail, however, was strongly dependent on methodology. Furthermore, relations between trophic levels were considered with respect to vertical distribution.     

Annual variation in gobiid larval density in the northern Baltic Sea

The highest densities of gobiid larvae along the Finnish Baltic coast from 1974 to 1996 were found in the Åland Islands and the Archipelago Sea. The annual variation in gobiid densities was three-fold (from 1· 1 to 3·3 larvae m⁻²) with peak densities in the years 1977 and 1992 and the lowest density in 1987. No long-term trends in the density were found. The earliest gobiids were caught in the first half of May and the occurrence of larvae peaked at the end of June to early July.Within breeding seasons there was a positive correlation between water temperature at a depth of 1 m and the density of larvae. The density of larvae, however, did not correlate with mean summer temperature or the mean temperature of the previous summer. Instead larvae production was negatively affected by the severity of the previous winter as indicated by the maximum ice cover in the Baltic. The density of larvae was independent of larval density of the previous year suggesting that gobiid production primarily depends on the spawning stock size and may hence be regulated by density-independent factors.     

Seasonal and short-term variation in denitrification and anammox at a coastal station on the Gulf of Finland,Baltic Sea

Benthic processes were measured at a coastal deposition area in the northern Baltic Sea, covering all seasons. The N₂ production rates, 90–400 μmol N m⁻² d⁻¹, were highest in autumn-early winter and lowest in spring. Heterotrophic bacterial production peaked unexpectedly late in the year, indicating that in addition to the temperature, the availability of carbon compounds suitable for the heterotrophic bacteria also plays a major role in regulating the denitrification rate. Anaerobic ammonium oxidation (anammox) was measured in spring and autumn and contributed 10% and 15%, respectively, to the total N₂ production. The low percentage did, however, result in a significant error in the total N₂ production rate estimate, calculated using the isotope pairing technique. Anammox must be taken into account in the Gulf of Finland in future sediment nitrogen cycling research. Handling editor: J. Cole     

Overview of Fish Consumption Rates in the United States

Contaminants that accumulate in fish may pose health risks and have raised concerns among consumers. Contaminated finfish and shellfish are possible routes of human exposure to toxic chemicals. Fish advisories are established to protect local populations from the consumption of contaminated commercial and non-commercially caught fish. Children, women of childbearing age, and subsistence fishermen or other highly exposed individuals who for socioeconomic or cultural reasons consume more fish than the general population are among the populations of concern from the ingestion of contaminated fish. Estimating exposure to a toxic chemical among fish-consuming populations requires knowledge about intake rates of fish and shellfish. Data on fish consumption rates come from various sources, including national, state, and local government studies. Although these data have their limitations, they serve as a source for deriving fish consumption rates that may be used by exposure assessors. Data on specific populations of concern are critical. Studies presented here show that ethnicity, age, and geographical region play an important role in fishing behavior and consumption. Results from studies on Native American populations show that this ethnic group eats fish at a higher rate than recreational anglers. This article summarizes data on fish consumption for various populations and provides a framework for evaluating data from these studies for exposure assessment applications.     

Food consumption and daily feeding periodicity: comparison between pelagic and demersal whiting in the North Sea

Pelagic North Sea whiting Merlagius merlangus fed at night, while demersal whiting fed by day. The estimated specific daily ration ranged from 4·38 to 7·84% in 1992 and from 3·99 to 10·31% in 1993 using the in situ rate of gastric evacuation. Using Andersen's evacuation model the specific daily ration ranged from 0·41 to 1·66% in 1992 and from 0·78 to 1·75% in 1993. The specific daily rations were significantly different where energy density of stomach content by length class of whiting was significantly different between the two layers and years. The fact that daily ration was related to prey composition and energy density of the prey and spatial distribution of the whiting, demonstrates the need for a sampling design that includes both pelagic and demersal layers when quantifying the food consumption of whiting.     

The Distribution of Hydrobiids and the Effects of Sediment Characteristics on the Population Dynamics of Hydrobia ventrosa in a Coastal Region of the Southern Baltic

The composition of the hydrobiid fauna in a coastal water of the southern Baltic was studied in 1990/91 at three stations with different sediment characteristics (grain size, organic content). Four species were found (Hydrobia ventrosa, H. ulvae, H. neglecta and Potamopyrgus jenkinsi). H. ventrosa was dominant at all stations. The mean hydrobiid abundances were 4,000 (stn. C), 18,000 (stn. B) and 40,000 (stn. A) ind./m² respectively. Abundance was found to correlate with the organic content of the sediment. The reproduction and growth of H. ventrosa was studied. Two reproduction phases were observed, one in summer and the other in late autumn. The autumn reproduction peaks were staggered owing to the different growth rates at the various stations. Possible correlations between the differences in shell size of H. ventrosa at the various stations and both sediment characteristics and abundance are discussed.     

麻塘湖水库鱼类种群及其饵料生物现状的初步研究

通过对怀宁县麻塘湖水库的鱼类种群及饵料生物组成进行的调查,鉴定出水生维管束植物的四个优势种,底栖动物２２种,浮游动物三大优势类群和鱼类３２种。结果表明该水库的鱼类年龄组成趋于低龄化。在此基础上,作者提出了恢复该水库鱼类资源和提高水库生态效益的初步意见     

Food limited survival of larval razorback sucker,Xyrauchen texanus,in the laboratory

Synopsis Razorback suckers in Lake Mohave, Arizona-Nevada, are suffering recruitment failure. Concomitantly, lake zooplankton levels are low and variable. We test, under laboratory conditions, the possibility that starvation is a cause of low recruitment. Razorback sucker larvae that were starved, received food too late, or were provided with insufficient food died between 20 and 30 d after hatching. Yolk absorption was at 8d after hatching, the critical period during which larvae must feed or most will die lies between 8 and 19d, and the point of irreversible starvation for individuals is between 19 and 23 d after hatching. Results support food-related mortality as a contributor to year-class failure of razorback sucker in Lake Mohave.     

布氏田鼠非取食性牧草消耗量的测定

布氏田鼠 (Ｍｉｃｒｏｔｕｓｂｒａｎｄｔｉ)为内蒙古典型草原区的主要害鼠之一[1,6 ,8,9] 其危害主要表现为与牛羊争夺牧草资源。因此 ,测定其牧草消耗量 ,是定量地衡量其危害程度 ,推算鼠害防治经济阈值的重要基础。在牧草生长季节 ,该鼠对牧草的消耗主要分为两个方面 ,即取食量和非取食性消耗量 (布氏田鼠咬断而未取食的部分牧草或者食物残屑 )。有关该鼠食性与食量的研究已有一些报道[2 ,3 ,5] ,但对该鼠的非取食性牧草消耗量则缺乏研究。为此 ,本文开展了这项工作 ,为定量估算该鼠的危害程度提供依据。1　材料与方法本项研究是于 1997…     

波罗的海放线菌的多样性

摘要:【目的】为了探索海洋放线菌的多样性,为发现新的药物先导化合物提供新菌源,我们分析了波罗的海的放线菌多样性及生物活性。【方法】采集100 份底泥样品,用7 种培养基分离放线菌809 株;去掉相同菌株后,选择280 株代表菌进行了初步分类鉴定;采用琼脂扩散法,检测了它们对5 种细菌、真菌的抗菌活性;用API ZYM system 测定了21 种酶的活性。【结果】用海藻糖-脯氨酸培养基和HV 培养基分离的放线菌中,稀有放线菌占60% 和63% ;波罗的海的放线菌有15 个属,其中3 个属是首次从海洋中分离     

Year-to-year variation in larval fish assemblages of the Southern North Sea

In order to test the temporal stability within and the reproducibility of larval fish assemblages between years, the larval fish assemblage at Helgoland Roads, North Sea (NE Atlantic) was quantitatively sampled almost daily from January 2003 to December 2005. The survey resulted in a total of 462 samples containing 50,632 larval fish of at least 42 taxa. In winter the larval fish assemblage was mainly dominated by larvae emerging from demersal eggs. This changed gradually to larvae hatching from pelagic eggs. Larvae from pelagic eggs dominated the ichthyoplankton assemblage in summer. A remarkably stable seasonality in terms of dominance patterns with recurring, season-specific fish assemblages was observed over the 3 years, despite substantial variation in environmental conditions such as a temperature difference of almost 20°C between summer and winter. The lesser sandeel (Ammodytes marinus), was the only species which showed significant fluctuations in abundance between the years. After removal of this species from the analysis, the dominance patterns of the remaining fish species were almost identical between years.     

Selectivity of fishing gears used in the Baltic Sea cod fishery

The Baltic cod (Gadus morhua) plays a very significant role in the Baltic Sea ecosystem being the major fish top predator and the most important commercial species for the Baltic Sea fishing industry. Consequently the management and understanding of the exploitation pattern of the stock is of major importance. Technical regulations, improving the selectivity of cod, have been a major management strategy and the Baltic Sea is likely to be the area where most fishing gear selectivity studies, focussing on size selectivity, have been conducted over time. The methodology for conducting and analysing selectivity data has been significantly improved in recent years. The subject is reviewed since the choice of methodology can have a significant effect on the interpretation of the outcome of selectivity experiments. Factors affecting the selectivity of trawl and gill nets are considered. Alternative ways to improve the size and species selectivity of trawls using selective devices are reviewed. Selectivity parameters from available literature are listed and the correlations of selectivity parameters to the mesh size for different gears are estimated. The historical legislation on selectivity is reviewed and the expected selectivity for trawls is estimated. Management considerations concerning the mortality of escaping and discarded fish and wider management impacts have to be considered if improving selectivity. The review is ended by conclusions including reflections on needed research in the future.