Population dynamics of Donax dentifer (Veneroida: Donacidae) in Bay of Bahía Málaga,Colombian Pacific during the "El Niño" 1997/1998

Donax dentifer is a dominant member of the sandy beach communities of the Colombian Pacific coast. A population of this bivalve was monthly sampled in Playa Chucheros at the Bay of Málaga, Colombian Pacific, between August 1997 and July 1998, during the "El Ni?o 1997/1998" phenomenon. Quantitative samples were taken in perpendicular and parallel to the coastal line transects to determine the population density and a length-frequency distribution. Qualitative samples were taken to study the reproduction and monthly length weight relationship. Sea surface temperature, dissolved oxygen, salinity and pH in the water was monthly registered in the sampling station. Additionally, a tagging-recapture experiment was performed to growth estimations. Results indicate a continuous reproduction cycle with two annual spawning seasons in December and March. The growth parameters of the non-oscillating von Bertalanffy growth function were K = 0.62 yr-1 and L infinity = 29.3 mm. Mortality (Z) was higher (2.65 yr-1) for small individuals (between 2 mm and 5 mm) while a lower Z value (1.71 yr-1) were obtained for larger ones (between 19 mm and 25 mm). An annual mean biomass value of B = 1.229 g ash-free dry weight m-2 and an annual somatic production of Psom = 1.215 g ash-free dry weight m-2 were estimated, which correspond to a Psom/B value of 0.988. Population density increased in November and April, but any population density pattern related with "El Ni?o" was evident. Low body weight during November-December seems to show a relation between reproductive cycle in D. dentifer and El Ni?o 97/98 event. The fluctuation in dissolved oxygen show a high correlation with parameters of the reproductive cycle, which could be related to assimilation process and body weight cycle. Growth in D. dentifer in the Colombian Pacific coast was faster than other Donax species, as can be expected for tropical bivalves mollusks in comparison whit high latitude bivalves. The mortality pattern suggest that the population was selectively affected by El Ni?o 97/98, due to smaller individuals are living in the lowest areas of the beach, where they are exposed to abnormal seawater conditions for a longer time. Individual and population production was higher for medium-size animals than each for small-size ones, which were the most abundant in the population.     

扁担塘螺类生产力的研究Ⅰ.铜锈环棱螺的周年生产量

１９９６—１９９７年对扁担塘螺类优势种之一铜锈环棱螺进行了周年研究,结果表明其种群含四个年龄组,其中１９９６年组生长最快,其带壳湿重瞬时生长率为４．１５,去壳干重瞬时生长率为３．４０。采用瞬时生长率法测算其周年生产量为：带壳湿重,１５．７７ｇ·ｍ－２·ａ－１;去壳干重,０．８６２４ｇ·ｍ－２·ａ－１。Ｐ／Ｂ系数基本一致,分别为０．５０,０．５１。铜锈环棱螺的生产量的去壳干重（Ｗｄ,ｇ·ｍ－２·ａ－１）和带壳湿重（Ｗｗ,ｇ·ｍ－２·ａ－１）满足下列关系：Ｗｗ＝１７．２０Ｗｄ。     

Spatial distribution and short-term changes of benthic macrofauna in Lake Balaton (Hungary)

Spatial and short-term changes in the composition and density of the macrobenthic fauna were studied in Lake Balaton, a large shallow lake in Central Europe (Hungary). Spatial differences were examined along five transects and short-term changes at two stations of different trophic state. The macrobenthos consisted almost exclusively of Tubificidae and Chironomidae of the species Chironomus gr. plumosus, Procladius choreus, Tanypus punctipennis, Microchironomus tener and Cladotanytarsus sp. The Oligochaeta biomass showed a significant short-term decrease from 1995 to 1998, and their average biomass proved to be 0.86 and 0.79 g WFW (wet formalin weight) m-2 in 1996 and 1997, respectively. Chironomidae showed significant spatial and short-term differences following variations in primary production. Higher primary production resulted in higher biomass (up to 153.4 g WFW m-2 and 9785 ind. m-2 in 1995) of Chironomus-Procladius community, while lower primary production resulted in a very low biomass and abundance of the predatory Procladius-Tanypus-Microchironomus community (average: 3.16 g WFW m-2 and 1311 ind. m-2 in 1997). As compared to other lakes of similar climatic conditions, the total production of oligohaetes and chironomids proved to be very low in 1996 and 1997 (49.2 and 54.1 KJ m-2 yr-1, respectively). The 90% of the average chironomid production of Lake Balaton in 1996 and 1997 belonged to Ch. gr. plumosus (5.63 and 5.13 g m-2 yr-1), P. choreus (4.3 and 3.47 g m-2 yr-1) and T. punctipennis (0.27 and 2.21 g m-2 yr-1). This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of growth pattern, sampling interval and number of size classes on benthic invertebrate production estimated by the size-frequency method

SUMMARY. 1. A hypothetical leech population with known initial density, initial weight, final weight and cohort production interval (CPI) was established. Production estimated by the size-frequency method for various growth patterns, mortalities, number of samples per CPI and number of size classes was compared with actual production estimated from daily growth and mortality by the increment-summation method. The population had either perfectly continuous reproduction or a perfectly synchronous cohort.
2. When size-classes were delimited in order to equalize the time spent in each size class, the deviations from actual production increased with decreasing number of size-classes and increasing mortality. For a population with perfectly continuous reproduction, production was only overestimated by 32% with an extreme mortality of 2.0% day⁻¹ and three size-classes. For a perfectly synchronous cohort, production was either underestimated or overestimated, depending on the first day of sampling. The deviations from actual production increased considerably with decreasing number of size-classes, increasing mortality and decreasing number of samples per CPI.
3. Differences between actual and assumed growth patterns may give underestimates or overestimates of more than one order of magnitude at high mortalities and few size-classes. It is concluded that knowing the actual growth pattern, the size frequency method will give realistic estimates of production in cases when normal cohort methods cannot be used. The estimate can be improved significantly by increasing the number of size classes and the number of samples per CPI.     

Composition, growth and conditionindex for a population of Poecilia reticulata (Pisces: Poeciliidae), in a pond in Heredia, Costa Rica

A pond population of Poecilia reticulata was studied in Santo Domingo, Heredia, Costa Rica, between September and November of 1998. The sex ratio was 1:0.49 (males:females). The mean total length was 34.43 +/- 7.26 mm for females, 23.50 +/- 2.24 mm for males and 12.27 +/- 3.41 mm for juveniles. The mean total weight was 0.69 +/- 0.48 g for females: and 0.16 +/- 0.05 g for males and 0.026 +/- 0.027 g for juveniles. The total length-weight relationship for the total population was P= 6 x 10(-5) Lt 3.3272 (r2 = 0.9613). The condition index equation was K = 25.755 e(0.004Lt) (r2 = 0.8925) for females and K = 26.767 e(0.003Lt) (r2 = 0.907) for males. The mean condition index was 31.29 +/- 0.55% for females and 28.52 +/- 0.19% for males. Both sexes reached the sexual maturity when the males and females overcame the 20.00 mm and 23.5 mm of Lt respectively.     

Current range condition in relation to land management systems in semi-arid savannas of Swaziland

Rangeland condition was assessed in the lowveld of Swaziland to determine the current status with emphasis on contrasting different land management systems and soil classes in two study areas. The assessment incorporated the grass and woody plant layer. The methods employed to evaluate the grass layer were ecological condition index (ECI) and weighted palatability composition (WPC). The government ranch had significantly higher ECI (mean 714.5) and WPC (mean 61) than the communal land (mean: ECI – 533.5; WPC – 48.7) and the game reserve (mean: ECI – 578.9; WPC – 47.9). The ECI and WPC values did not differ between the soil classes in most cases (range: ECI 551.5–645.9 and WPC – 43.7–57.6). The density of all woody plants and encroaching plants alone were the highest in communal land. Basal cover ranged from poor (2–3%) to good (>5%), while bare ground was rated from low (<1%) to high (>5%). Overall results showed great variability of studied variables at site and landscape levels of resolution. Generally, the grass layer was rated between fair and good when assessed on the basis of ecological and palatability merits. There was a clear indication of advancement of bush encroachment.     

Productivity of a herbivorous pupfish population (Cyprinodon nevadensis) in a warm desert stream

Production and food intake by an herbivorous pupfish population ( Cyprinodon nevadensis amargosae ) living in the outflow of a thermal artesian well (Tecopa Bore) near Death Valley, California is described. Water issues from the ground at 47.5° C and cools 8.12° C before leaving the study area 300 m from the source. High stream temperatures restricted the pupfish population to some 41 % of the study area, with a resulting mean density of 89 individuals m⁻² (range = 13 to 196m⁻²). Biomass estimates ranged from 7 kcal m⁻² to 42 kcal m⁻². The mean annual standing crop of pupfishes (24 kcal m⁻²) turned over about five times annually. Growth rates were highest in juveniles (♂= 9.5% day⁻¹) and slowest in large adults (♀= 08% day⁻¹). Monthly production ranged from 22 kcal m⁻² in September to 3 kcal m⁻² in July and August. Pupfish in Tecopa Bore fed on algae and detritus, ingesting 1941 kcal m⁻² yr⁻¹ or 17.5% of the annual net primary production. 119 kcal m⁻² yr⁻¹ was deposited in growth. This latter value is approximately ten times greater than values previously reported for large carnivorous fishes but is comparable lo values reported for herbivorous fishes under pond culture.     

水母雪莲细胞生物反应器悬浮培养

Cell suspension culture of Saussurea medusa Maxim. was established in a 2 L stirred bioreactor for flavonoids production. After 12 days of culture, the biomass was 10.35 g DW·L-1, containing 428.6 mg/L flavonoids, which was 4.14% of the biomass (dry weight) under the condition of 25 ℃ and light intensity lower than 5 μmol·m-2·s-1. The utility pattern of sugar, change of dissolved oxygen and oxygen uptake rate were also studied.     

Dynamics and structure of a Velia caprai (Heteroptera) population in a South Swedish stream

Population density was estimated monthly by means of direct counts for 16 consecutive months. Capture-recapture experiments revealed that 9–22% of the population was observed by this technique. Most nymphs appeared in June, and the presence of nymphs in September suggests a second generation. There was a strong positive correlation between summer surface drift and mean annual population density for five out of six sections studied. In July-August the sex ratio was near equal, while in September females began to dominate. The bias towards females was strong until new imagines emerged in July. From September a marked weight dimorphism was observed between the sexes. Food limitation, and skewed sex and weight ratios implied intersexual competition in this population. Brown trout possibly affected the population density in one section with less shelter. Wing dimorphism was observed in July and August. Macropterous individuals represented a low percentage (<17%) and were only observed in sections with high densities.     

Variability in annual recruitment success as a determinant of long-term and large-scale variation in annual production of intertidal Wadden Sea mussels (<Emphasis Type="Italic">Mytilus edulis</Emphasis>)

To understand the background of the strong variation and recent decline of stocks and production of mussels (Mytilus edulis) on tidal flats of the Wadden Sea, we analysed long-term (twice-annual for 26 years) and multi-station (15 sites) estimates of numbers, mean individual weights, biomass, and annual production on Balgzand, a 50-km² tidal-flat area in the westernmost part of the Wadden Sea (The Netherlands). Somatic production was estimated from summed growth increments of soft tissues per half-year period and expressed in ash-free dry mass (AFDM). In adults, positive values in spring/summer regularly alternated with negative values in autumn/winter, when up to ∼25% (mean: 14%) of individual weight gains in the preceding season were lost. No weight losses were observed during the first winter of the life of mussels. The 26-year mean of net somatic tissue production P amounted to 5.5 g AFDM m⁻² a⁻¹ at a mean biomass B of 3.2 g AFDM m⁻²; the ratio P/B varied strongly with age composition of the mussel population and ranged between 0.5 and 3.0 a⁻¹ (mean: 1.7). Within the restricted areas of mussel beds, mean biomass and annual production values were two orders of magnitude higher. In the Wadden Sea, mussel beds cover a typical 1% of extensive tidal flat areas. Numerical densities of recruits showed straight-line relationships with subsequent life-time year-class production. Once recruits had reached an age of ∼10 months, their numbers predicted subsequent production within narrow limits. Production per recruit averaged 0.21 g AFDM for 10-mo recruits and was not related to recruit density. Local variation in annual production varied strongly, with maximal values between mid-tide and low-tide level, where recruitment was also maximal. Production per recruit was higher at low than at high intertidal levels. Frequently failing recruitment is indicated as the main cause of declining mussel stocks in the Wadden Sea. As in other bivalve species, a declining frequency of the occurrence of cold winters appears to govern declining recruitment success and consequently declining production.     

Energetics of a population of Asellus aquaticus (Crustacea, Isopoda): respiration and energy budgets

SUMMARY. Respiration of Asellus aquaticus was determined on tiine occasions throughout the year using a Gilson differential respirometer. On each occasion the determination was made at the lake temperature, which ranged from 2 to 18°C, Linear regressions were derived for log oxygen uptake against log dry weight. There was a significant difference between mean rates of oxygen uptake at the various temperatures but the slopes of the regression lines, which varied from 0,62 to O.85 with a mean of 0,76, were not significantly different.
The temperature of the lake was monitored throughout the year. Using the relationship of oxygen uptake against temperature, and estimates of population density obtained previously, the total annual respiration of the population was calculated as 4571 ml O₂ m^-2, equivalent to an energy loss of 92.3 kj m^-2 year^-1 from a mean biomassof 752 mg m^-2.
Consumption of decayed Alnus glutinosa leaves and faecal production rates, and thus assimilation efficiency, were determined by gravimetric methods in the laboratory at 10°C, close to the mean temperature of the lake (10.rC), In the four size classes investigated, larger animals consumed more food per individual, but less on a weight specific basis. However, it was shown that consumption was greater if the leaf material was more highly decomposed, Assimiliation efficiency was calculated as 23%.
Using data for respiration, population density and the assimilation efficiency, the annual population energy budget was estimated as (kJ m^-2year^-1): consumption, 568.9 (100%); production, 38.5 (6.8%); respiration, 92.3 (16.2%); faeces, 438.1 (77%). The significance of these energy values, and the ecological efficiencies calculated from them, are discussed in relation to other published work.     

Aspects of the ecology of bream, Abramis brama (L.), in a gravel pit lake and the effects of reducing the population density

The growth of bream, Abrumis brumu (L.), in a gravel pit lake was considered to be good in 1982/1983 (L_x=663cm, K=0.105). Theadult breampopulationwasdominated by the 1973and 1976 year-classes. These year classes still formed most of the spawning population in 1987, but had grown very little (<2 cm) in the previous 5 years. In November 1987, 158 kg ha⁻¹ of bream were removed from this lake and in I988 the remaining bream population showed an increase in growth (mean length by 2.7 cm and mean weight by 0.5 kg) and condition (1.87 in 1987 to 2.09 in 1988) in one growing season. This additional growth of an ageing stunted bream population is considered to be the result of an increased food supply after reducing the fish density.     

The production of brown trout, Salmo trutta in tributaries of the Upper Wye, Wales

The population density, age structure, biomass, growth and production of brown trout were investigated in four tributaries of the upper River Wye. The populations at each site were largely maintained by immigration from nursery areas. Abundance of separate year classes at sites on the three largest tributaries reached a peak at age 2+. On the smallest stream numbers reached a peak at 1+. Recruitment occurred throughout the year but decreased with age of year classes. Maximum O+ densities ranged from 0.04 to 0.89 m⁻², and >0+ densities from 0.13 to 0.59 m⁻². Average total biomass in 1975 ranged from 2.6 to 14.2 g m⁻². Within the study sites annual trout production in 1975 ranged from 2.9–19.7 g m⁻². Production values were dependent on age structure and population mobility at the study sites. In the three largest streams 2+ and 3+ fish contributed 66.3–88.3% of total production whilst 1+ and 2+ fish contributed 74.5–84.5 % of the total in the smallest stream. The mobile (non-resident) component of the population accounted for up to 60–70% of production at certain times of the year, but over the year (1976) accounted for =30 % of total production. The resident component of the highest annual production value (19.7 g m⁻²) was estimated to be between 15.0 and 18.2 g m⁻².     

深圳福田无瓣海桑-海桑林能量的研究

在研究生物量、生产力的基础上,对深圳福田无瓣海桑-海桑林中2种红树植物海桑和无瓣海桑各组分的干重热值、林分能量现存量、年能量净固定量进行了研究．结果表明,各组分样品干重热值有一定的差异,树叶干重热值最高,纫根干重热值最低;海桑各组分样品干重热值比无瓣海桑相应组分稍高．林分能量现存量(1999年10月)为84774．72kJ·m^2,其中无瓣海桑种群能量现存量为54693．26kJ·m^-2,占林分总的64．54％,海桑种群能量现存量为30051．46kJ·m^-2,占林分总量的35．46％．林分凋落物的能量归还量(1999年)为24549．54kJ·m^-2·年^-1,其中无瓣海桑种群的能量归还量为17223．99kJ·m^-2·年^-1,占总林分的70．16％,海桑种群的能量归还量为7325．55kJ·m^-2·年^-1,占总林分的29．84％．林分能量净固定量为50391．4kJ·m^-2·年^-1,其中无瓣海桑种群和海桑种群的能量净固定量为分别为31778kJ·m^-2·年^-1和18613．4kJ·m^-2·年^-1．     

军山湖耳河螺的种群动态及周年生产量

2005年4月～2006年3月期间,对军山湖耳河螺(Rivularia auriculata)进行了周年逐月采集,分析了耳河螺的种群动态,并采用瞬时生长率法测算了周年生产量.结果表明种群含三个年龄组,年均生物量13.37 g·m^-2,年均密度8.12 ind·m^-2.种群密度峰值出现在8月为24 ind·m^-2,次年3月份有最低值为3.2 ind·m^-2.生物量峰值则出现在9月为30.32 g·m^-2、次年3月生物量有最小值为3.872 g·m^-2.耳河螺周年生产量(带壳湿重)为3.5592(g·m^-2·a^-1),周年P/B系数为0.27.与其他研究比较,结果较为合理.P/B系数较低,说明这一资源日趋贫乏,需要合理的保护利用.     

Characteristics of the spawning migrations of brown trout, Salmo trutta L., and rainbow trout, S. gairdneri Richardson, in Great Lake, Tasmania

Upstream spawning migrations of mature brown trout, S. trutta , and rainbow trout, S. gairdneri , were studied in Liawenee Canal, Great Lake from 1949 to 1985. Brown trout migrations normally occurred from early April to mid-May and rainbow trout from late August to early November. In 1983, 16 425 brown trout and 1338 rainbow trout passed through a fixed upstream diversion trap. Brown trout spawning migrations occurred predominantly over the temperature range 6–10° C, while rainbow trout migrated predominantly over the range 5–11° C. Migrations peaked at water temperatures of 7.6°C (males) and 7.8°C (females) for brown trout, and 8.3°C (males) and 9.6°C (females) for rainbow trout. Rainbow trout migrations occurred at high flow conditions and were positively correlated with canal flow increases, while brown trout migrated under low canal flow. Mean length, weight and condition of rainbow trout of both sexes decreased significantly during migrations. Female brown trout decreased in weight and condition but not in length; male brown trout did not change in condition despite decreases in both length and weight during migrations. Overall sex ratio was 2:1 (female:male) for both species, with the relative proportion of male fish decreasing as migrations progressed. Age composition changed during migrations; dominant age classes were 3 < 4 < 5 + years for both species. Comparison of length, weight, condition and age revealed minor changes during the 37-year period 1949–1985.     

东海赤潮高发区春季浮游动物生态特征的研究

根据2002年4～5月东海122°～123°30′E、29°～32°N水域海洋综合调查资料,对东海赤潮高发区浮游动物的数量分布、群落特征、种类组成及优势种等进行了分析．结果表明,在调查区共鉴定出饵料浮游动物128种[不含16种浮游幼虫(体)和仔鱼],分5门12大类,以桡足类占优势(40种,31．25％)．浮游动物群落以广温广盐生态类群为主．中华哲水蚤(Calanus sinicus)为最主要优势种(142．10ind·m-3,68．09％)．总生物量均值为243．80mg-m3(55．53～773．92mg·m-3),最高密集区(>500mg·m-3)位于长江口30°45′～31°15′N、122°45′～123°15′E水域．饵料生物量均值为195．96mg·m13(55．53～496．09mg·m。),呈长江口(30°30′N以北)水域高于舟山岛东南水域、长江口外海(122°45′E以东)高于近海水域的分布趋势．多样性指数(H′)均值为2．12(1．09～3．73)．长江口水域多样度、均匀度和丰富度低,优势度大,反映出浮游动物群落结构不够稳定．采用逐步回归分析得知,影响本区春季浮游动物生态特征值分布的主要因子是水温、硅藻和甲藻．     

Habitat and substrate influences on population and production dynamics of a stream caddisfly, Ceraclea ancylus (Leptoceridae)

SUMMARY. Population and production dynamics of Ceraclea ancylus (Vorhies), a leptocerid caddisfly with a univoltine life cycle, five larval instars, and a single cohort population, were examined in Brashears Creek, Kentucky. A systematic sampling approach that included analysis in riffle, pool, and waterwillow bed habitats was used and fourteen sampling transects were taken across Brashears Creek between May 1971 and July 1972. For each of the 70 m² samples taken along a transect, the depth, habitat, and substrate type were recorded. The number of C. ancylus cases and numbers and dry weights of each larval instar were determined. The majority of the C. ancylus population was in the second larval instar in July, the third larval instar in August, the fourth larval instar in September, and the fifth larval instar from October through May. The spring population was 30% of the early instar maximum estimated the previous August. The spatial distribution of C. ancylus reflects a logarithmic pattern with early instar larvae more highly clumped than the late larval instar and pupal populations. Initial standing stock estimates were less than 1% of the standing stock biomass. A production estimate of 9.9 mg/m²·year (dry weight) was determined using the instantaneous growth method, Allen's Curve method, and the Hynes method of estimating secondary production. Turnover ratios (7.0 annual TR, 5.7 cohort TR) were higher than estimates reported as typical for benthic macroinvertebrates because of the low initial to final mean individual weight of the C. ancylus larvae (0.4%). Production estimates calculated for C. ancylus populations in waterwillow bed (4.4 mg/m²·year) and pool (13.7 mg/m²·year) habitats were less than calculated for the riffle population (19.9 mg/m²·year). The annual turnover ratio (10.2) was higher in the pool population than in other habitats because of spring larval migration into the pool from other habitats. A trend of higher production estimates with larger sized substrate particles and increased numbers of particles may reflect the increase in available food sources or attachment sites. The accuracy of production estimates and their applicability to water resource management may be limited by a failure to consider the spatial distributions of the population being sampled and the tendency for sampling procedures to be confined to single habitats.     

大棚辣椒最佳钾肥用量及运筹

以台湾‘长香’辣椒Capsicum frutescens品种为材料,通过设置钾肥横向与纵向施肥的田间试验,探讨辣椒最佳钾肥用量及其运筹。结果表明,在设定氮、磷肥施用量分别为15.0、3.5 kg·667m-2的条件下,钾肥不同施用量对辣椒的株高、幅宽、茎粗的长势及果长、果粗、单果重等品质均有明显的影响,辣椒产量(y)与钾肥施用量(x)两者呈y = -2.2743x2 + 53.402x + 802.45的相关性(r2 = 0.973),钾肥最佳施用量为11.74 kg·667m-2;在同样条件下,钾肥施用量12.00 kg·667m-2,按基肥与追肥不同比例进行施用,辣椒株高、幅宽、茎粗的长势及果长、果粗、单果重等品质与产量均有所差异,其基肥∶追肥按2∶8的配比进行运筹施用,辣椒品质与产量均明显优于其他配比。