Annual Turnover Ratio Research Articles

Bionomy and Secondary Production of Midges Inhabiting Wood: Unravelling Linkages at a Large River System

In the near pristine free-flowing section of the Parana River the biomass, organic matter, annual and cohort production and turnover ratios of midges inhabiting LWD were estimated. Richness and frequency of occurrence of the stages, genera and functional feeding groups of midges were calculated. Generalized linear mixed effect models were performed to evaluate whether environmental and woods characteristics predicted the biomass of midges. Eggs, larvae, pupae and imagoes of 32 taxa and functional groups were collected. Biomass was of 44.79 mg/m2 and AFDW was of 28.1 mg/m2, on average, with the maximum values obtained for collectors and shredders. Water transparency was the only one significant predictor of midge stocks. Annual production ranged between 190 and 858 g/m2 year and P/B between 31 and 224. The natural free-flowing conditions and high food availability, provide woody substrates that favour a high production and overlap in resource utilization, thus supporting a high diversity of midges.

Factors driving spatial and temporal variation in production and production / biomass ratio of stream-resident brown trout (Salmo trutta) in Cantabrian streams

Summary 1. The objective was to identify the factors driving spatial and temporal variation in annual production (PA) and turnover (production/biomass) ratio (P/BA) of resident brown trout Salmo trutta in tributaries of the Rio Esva (Cantabrian Mountains, Asturias, north-western Spain). We examined annual production (total production of all age-classes over a year) (PA) and turnover (P/BA) ratios, in relation to year-class production (production over the entire life time of a year-class) (PT) and turnover (P/BT) ratio, over 14 years at a total of 12 sites along the length of four contrasting tributaries. In addition, we explored whether the importance of recruitment and site depth for spatial and temporal variations in year-class production (PT), elucidated in previous studies, extends to annual production. 2. Large spatial (among sites) and temporal (among years) variation in annual production (range 1.9–40.3 g m−2 per year) and P/BA ratio (range 0.76–2.4 per year) typified these populations, values reported here including all the variation reported globally for salmonids streams inhabited by one or several species. 3. Despite substantial differences among streams and sites in all production attributes, when all data were pooled, annual (PA) and year-class production (PT) and annual (P/BA) and year-class P/BT ratios were tightly linked. Annual (PA) and year-class production (PT) were similar but not identical, i.e. PT = 0.94 PA, whereas the P/BT ratios were 4 + P/BA ratios. 4. Recruitment (Rc) and mean annual density (NA) were major density-dependent drivers of production and their relationships were described by simple mathematical models. While year-class production (PT) was determined (R2 = 70.1%) by recruitment (Rc), annual production (PA) was determined (R2 = 60.3%) by mean annual density (NA). In turn, variation in recruitment explained R2 = 55.2% of variation in year-class P/BT ratios, the latter attaining an asymptote at P/BT = 6 at progressively higher levels of recruitment. Similarly, variations in mean annual density (NA) explained R2 = 52.1% of variation in annual P/BA, the latter reaching an asymptote at P/BA = 2.1. This explained why P/BT is equal to P/BA plus the number of year-classes at high but not at low densities. 5. Site depth was a major determinant of spatial (among sites) variation in production attributes. All these attributes described two-phase trajectories with site depth, reaching a maximum at sites of intermediate depth and declining at shallower and deeper sites. As a consequence, at sites where recruitment and mean annual density reached minimum or maximum values, annual (PA) and year-class production (PT) and annual (P/BA) and year-class P/BT ratios also reached minimum and maximum values.

THE LIFE CYCLE, POPULATION DYNAMICS, GROWTH AND SECONDARY PRODUCTION OF BITHYNIA GRAECA (WESTERLUND, 1879) (GASTROPODA) IN LAKE KERKINI, NORTHERN GREECE

The life cycle, population dynamics, growth and secondary production of the freshwater prosobranch snail Bithynia graeca (Westerlund 1879) were studied in the artificial Lake Kerkini (Serres, Northern Greece) where water volume and depth fluctuate dramatically. B. graeca faces deterministic and stochastic aspects of this environment. Growth and reproduction were studied for two populations, one being covered by the water almost throughout the year and the other not. B. graeca is a semelparous annual freshwater snail whose life expectancy decreased with increasing age. Maturity was attained 4 months earlier for the first population. Reproduction took place in spring. The majority of adults died after egg-laying. Growth rate was rapid during spring, and activity ceased during winter. B. graeca is a prosobranch snail whose short turnover time (77.9 and 84.3 days) was similar to that seen in freshwater pulmonate snails. Productivity was assessed in two ways, by a size frequency method and by using cumulative biomass. Observed values, for the two methods respectively, were for mean biomass 18.53 and 22.8 g dry body weight/m 2 , for annual production (P) 86.81 and 88.38 g dry body weight/m 2 or 9.56 gC/m 2 ·year respectively, and for annual turnover ratio (P/B ‐ ) 4.68 and 3.87/year. Net reproductive rate Ro was 2.99 and per capita rate of increase (rc) was 0.091.

The influence of environmental factors on the population dynamics, reproductive biology and productivity of Echinogammarus marinus Leach (Amphipoda, Gammaridae) in the Mondego estuary (Portugal)

Abstract The population density of Echinogammarus marinus in the Mondego estuary changed throughout the year, with a maximum during spring. The lowest densities were found in the north arm of the estuary, and the highest ones in the inner areas of the south arm. Higher densities appeared associated with the presence of muddy deposits under Fucus vesiculosus (Phaeophyta) and also with the presence of green macroalgae biomass over the sediments. Females were morphologically recognisable at smaller sizes than males, but males became larger than females. Fecundity increases with the size of females and is influenced by temperature and salinity. Sexual activity and recruitment take place continuously throughout the year, although it almost ceases by the end of winter. Present results are in opposition to the hypothesis of discontinuous recruitment presented in a previous study. Productivity (ash free dry weight- AFDW) was estimated at 1.74 to 2.45 g·m–2·year–1 in the north arm of the estuary corresponding to an annual turnover ratio ( P / B ) of 4.14 to 6.18. In the south arm, productivity was estimated at 1.96 to 2.74 g AFDW·m–2·year–1 in the middle section ( P / B of 4.68 to 6.56), and at 3.85 to 5.38 g AFDW·m–2·year–1 in the innermost sampling area ( P / B of 4.54 to 6.36). Differences in productivity appeared to depend only on population density, while annual P / B ratios were similar over the estuary. Evidence was found that several features of E. marinus population dynamics were dependent on environmental factors resulting from the particular estuary hydraulic regime.

ASPECTS OF LIFE CYCLE, POPULATION DYNAMICS, GROWTH AND SECONDARY PRODUCTION OF THE PULMONATE SNAIL CEPAEA VINDOBONENSIS (FÉRUSSAC, 1821) IN NORTHERN GREECE

The life cycle, population dynamics, growth and secondary production of the land snail C. vindobonensis were studied in northern Greece. Demographic analysis of the populations of C. vindobonensis revealed that a) three cohorts were present in the field throughout the year, b) the reproductive period started in late April-May and the newly hatched snails appeared in the beginning of June, and c) increased growth rates were observed during spring and early summer, but also during autumn for the newly hatched snails. According to von Bertalanffy's method C. vindobonensis needs 7 years to attain its maximum size measured in the field. Mortality rate is very high during the first year of life, while life expectancy is higher during the second year of life and decreases afterwards. Net reproductive rate (R,,) was equal to 3.1 and the finite capacity for increase (antilogy,.) was equal to 1. Estimated annual secondary production with Hynes' frequency method revealed a mean standing crop (B) of 0.99 g/m2/year and a production (P) of 1.3 ± 0.11 g/m2/year. Annual turnover ratio (P/B) was equal to 1.31.

Life history and production of Hyalella azteca (Crustacea: Amphipoda) in a hypereutrophic prairie pond in southern Alberta

The life history and production of the amphipod Hyalella azteca were studied over an 18-month period in a hypereutrophic prairie pond in southern Alberta, Canada. The population reproduced once a year, with breeding commencing in June and continuing until August. Population density was highest in June. The mortality rate of the adult population increased with the onset of reproduction, and remained high until the end of winter. The population density was lowest during winter and early spring (January to May). Biomass (B) fluctuated in a similar manner to population density, but the peak biomass occurred in August and September. Annual production (P) was 23.12 g∙m−2 (dry weight), estimated by the size-frequency method. The corresponding annual turnover ratio (P/B) was 5.68. The unusually high annual production and turnover ratio are attributed to the high density and large adult size of this population.

Population Dynamics, Growth and Productivity of Abra ovata (Mollusca, Bivalvia) in the Evros Delta (North Aegean Sea)

AbstractMonthly samples of Abra ovata were collected during February 1983‐January 1984 in the Evros Delta (N. Aegean Sea). Population density (mean annual value = 2407.5 ind · m−2) was characterized by seasonal variation. An analysis of the length frequency distributions shows that one annual recruitment of juveniles (> 2 mm) occurred in October‐January; and also that, throughout the year, two age groups existed in the population. One growth ring was formed on the shells of the oldest age group during July‐August.Mean growth in shell length can be described by Bertalanffy function. A positive correlation existed between shell length and decalcified dry weight.Secondary production in A. ovata, calculated by the instantaneous growth method, showed a mean biomass of 29.221 g dry weight m−2yr−1, a productivity of 17.086 g dry weight m−2yr−1 and an annual turnover ratio of 0.59.

Population dynamics and production of the rocky stream-dwelling fish Garra ceylonensis (Cyprinidae) in Sri Lanka

ABSTRACTA population of Garra ceylonensis in a rocky, hill stream was studied by monthly sampling over a period of two years. The monthly population density, which varied from 1.28 to 4.16 m-2 with a mean of 2.37 m-2, was negatively correlated with the water speed. Asymptotic length (L∞) and the growth constant (K) were found to be 180.5 mm total length and 0.62. Maximum size observed was 174 mm, which is attained in about five years, but 99% of the population had a life expectancy of less than 3.4 years. The overall male to female ratio of the population was 0.58. The sex ratio was 1.0 in smaller size classes but decreased steadily with increasing size. There was a major spawning season following the main rainy period in contrast to the trend of most tropical freshwater fish species, which show enhanced breeding during the rainy season. The mean length and age at sexual maturity in females appear to be 109 mm and eighteen months. Fecundity varied between 740 and 4390. Average longevity and natural mortality were 4.8 years and 1.86. The mean biomass, average annual production and turnover ratio of the population were about 23.7 gm-2 wet weight, 41.2gm-2 and 1.7, respectively.

Energy flux in a natural population of the land snail Eobania vermiculata (Müller) (Gastropoda: Pulmonata: Stylommatophora) in Greece

Survivorship, production, mortality rate, consumption rate, assimilation, and growth and ecological efficiencies were studied in a natural population of the land snail Eobania vermiculata in Greece. Eobania vermiculata may take 5 years or more to reach maximum size (33 mm). Mortality rate and life expectancy decreased with age. Net reproductive rate was 3.4 and per capita rate of increase was 1.0. Energy flux in E. vermiculata was studied using Urtica dioica and Lactuca sativa as food. The highest daily consumption and assimilation rates (weight specific) were observed in newly hatched animals and the lowest in adults. Assimilation efficiency, mean monthly production, and gross growth and ecological or net growth efficiencies fluctuated with the season and the physiology of the snails. Snails fed U. dioica showed higher assimilation, gross growth, and net growth efficiencies than those fed L. sativa. Energy flow through the E. vermiculata population was 78.9 cal∙m−2∙year−1 (1 cal = 4.1868 J), mean assimilation efficiency was 52% if the snails were fed U. dioica only, and the ingestion rate was 19.5%. When E. vermiculata was fed U. dioica during its lifetime, 4.26% of the total assimilated energy was used for egg production, 10.2% for growth, and 87.8% for metabolic energy. Annual secondary production gave a mean adult density of 4.1 individuals/m2, a mean annual standing crop (biomass) of 6.8 g∙m−2, and an annual production of 13.9 ± 1.8 g∙m−2 or 2859.5 mg C∙m−2. The annual turnover ratio, or productivity rate constant, was 2.0.

Population ecology of the paddy field‐dwelling fish Channa gachua (Günther) (Perciformes, Channidae) in Sri Lanka

A population of Channa gachua in a small irrigation canal that supplies rice fields was studied by monthly sampling over 2 years. The population density was positively correlated with the rainfall and varied from 0.34 to 0.95 individuals m−2. The growth parameters of the von Bertalanffy growth equation determined on monthly size–frequency data were Lx= 179 mm total length and K=0.50. Overall male to female ratio was 0.82 and there were more females than males in the middle size classes. Spawning occurred throughout the year, but all evidence indicated enhanced breeding during major rainy periods of May to July and October to December. The length at first spawning was 102 mm, which is reached in about 20 months. Fecundity, which varied between 389 and 2130, was positively correlated with gonad weight, body weight and total length. Longevity and natural mortality were estimated as 6 years and l.27 yr−1, respectively. However, 99% of the population appeared to live for only 3 years. The mean biomass, average annual production and turnover ratio of the population were 7.35 g m−2, 12.06 g m−2 and 1.64, respectively.

The life cycle, population dynamics, growth and secondary production of the snail Xeropicta arenosa Ziegler (Gastropoda: Pulmonata) in northern Greece

The life cycle, population dynamics and secondary production of the xerothermophilic land snail Xeropicta arenosa were studied in northern Greece. The study of biology and the demographic analysis of the populations of X. arenosa revealed that it is a semelparous annual species. Reproduction takes place in autumn and the majority of the adults die after egglaying. Growth is continuous throughout the year and no seasonal fluctuations occur. Estimation of annual secondary production with the Hynes' size frequency method revealed a mean standing crop (aa) of 0.075 g m-2 year-1 and a productivity (P) of 0.267+ 0.043 gm-2 year-1. The annual turnover ratio (P/) was equal to 3.56.

東北地方におけるヒゲナガカワトビケラ属２種の生産量について

Production was estimated for the co-existing net-spinning caddisflies, Stenopsyche marmorata and S. sauteri, using the instantaneous growth method, in the Mamigasaki River in Yamagata, Tohoku District. S.marmorata was bivoltine, whereas S.sauteri was univoltine. Annual production for S.marmorata was calculated to be 15.47 g dry weight·m-2 · yr-1, which was the highest value of many reported for Trichoptera, excluding unusual conditions. Production for the overwintering generation of S.marmorata was roughly twice as large as that of the summer generation. Higher production was attained by the overwintering cohort because of heavier fifth instar body weights. Annual production for S.sauteri was 1.08 g dry weight · m-2·yr-1, which was within the range of values reported for many species of Trichoptera. Annual turnover ratio (P/B) was 8.99 for S.marmorata and 3.93 for S.sauteri. Cohort turnover ratios were 5.25 for the overwintering generation and 4.98 for the summer generation. Cohort turnover ratios for the two species were within the range observed for aquatic invertebrates.

Benthic Macrofaunal Production of Browns Bank, Northwest Atlantic

Benthic macrofauna of the coarse sediments of Browns Bank, off southwest Nova Scotia, Canada were sampled with a modified 0.5-m2 Van Veen grab; 29 stations from 1983 to 1985. Production was estimated from alcohol-stored biomass by multiplying by the annual turnover ratio, P:B, of each species. The latter was determined from an empirically derived relationship using known or estimated lifespans. Benthic macrofaunal production averaged 64 g wet weight∙m−2∙yr−1 on Browns Bank, markedly lower than the 193 g wet weight∙m−2∙yr−1 in the mixed and finer sediments of the Bay of Fundy. Other community characteristics, such as the number of polychaete and amphipod species for the two areas were similar, which we attribute to the similar geological ages of the sediments. Prey consumed by juvenile age 0 haddock (Melannogrammus aeglefinus) consist mostly of deposit-feeding macroinfauna which produce ~1.8 × 104 t wet biomass per year, representing ~8% of the total production of Browns Bank. Two linked hypotheses are proposed to account for the suitability of Banks as juvenile gadid feeding grounds: rapid rates of suspension of macrofauna by strong tidal currents; and drifting animals are of a suitable size and kind for juvenile haddock feeding.

Estimates of annual production for some aquatic insects from the La Trobe River, Victoria

Annual production was estimated by the size-frequency method for Ephemeroptera (Tasmanocoenis tonnoiri, two species of Baetis, Atalonella spp., Atulophlebioides sp.), Plecoptera (Leptoperla spp.) and Trichoptera (Ecnomus sp.) at four sites on the lowland section of the La Trobe River. Annual production (P) of individual ephemeropteran species (or genera) varied from 0.02 to 0.7 g m-2 while total annual production of this order at two sites was 0.7-1 . 5 g m-. Annual production of Leptoperla spp. was 0.03 g m-2 at one site while Ecnomus sp, averaged 2 g m-2 at two sites. Estimates of annual production were subject to an error of at least t 50%. Annual turnover ratios (P/B; B is mean biomass) varied from 9 to 19 and were three to four times higher than published values for similar-sized macroinvertebrates in the temperate zone (generally < 15°C mean annual habitat temperature). This probably resulted from the higher average temperatures (17-18°C) at most sites.

Secondary production of four sublittoral, soft-sediment amphipod populations in the Bay of Fundy

Estimates of secondary production by cohort summation of losses and size–frequency methods were made on the four most abundant amphipods at an 80 m deep station on a soft sediment in the southwestern mouth of the Bay of Fundy. Production and annual turnover ratios (production:biomass ratio (P:B), in parentheses) for the 1978 year class, expressed as grams wet preserved weight per square metre per year, were as follows: Haploops fundiensis, 0.505 (1.3); Photis reinhardi, 0.370 (2.8); Casco bigelowi, 1.210 (2.5); Harpinia propinqua 0.066 (3.1). The P:B ratios found were closest to those calculated by the empirical method of Robertson when an accurate estimate of life-span was available.

The life history of Dicosmoecus atripes (Hagen) (Limnephilidae: Trichoptera) in a Rocky Mountain stream of Alberta, Canada

Dicosmoecus atripes (Hagen) has a 2-year life cycle in Dyson Creek, Alberta, a second order foothills stream of the eastern Canadian Rockies. Emergence and oviposition occur from August to mid-October. The first winter is spent as first instar larvae, the second as inactive fifth (final) instars in a form of diapause. No growth was observed in overwintering first instar larvae, and a significant (P < 0.05) weight loss was recorded in overwintering fifth instar larvae. Temperature seems to be the most important factor responsible for the 2-year life cycle. Annual production was estimated at 91.4 mg∙m−2∙year−1, with an annual production and biomass turnover (P/B) ratio of 4.97. Larval diet and microhabitat changed between instars. The proportion of diatoms in the diet of early instar larvae was significantly (P < 0.001) greater than that of third and later instars. Early instar larvae inhabit stream margins, while larvae of third and later instars were mainly found in midstream reaches. Larvae of all instars preferred pools to riffles. Abiotic factors important in microhabitat selection seemed to differ between larval instars.

Methods for estimating secondary production in marine Amphipoda

For the 1971 year-class of Pontoporeia femorata from St. Margaret's Bay, N.S., secondary production was 11.06–13.61 g wet weight/m2 and annual turnover ratio was 3.64–4.78 as measured by three methods. These included cohort summation of losses, integrated production from the Allen curve, and size frequency, or modified Hynes methods. Sampling bias against early life history stages of amphipods collected with sieve meshes [Formula: see text] can be corrected by back calculation from population data thus enabling cohort-based estimates of secondary production to be made.Key words: secondary production, annual turnover ratio, Pontoporeia femorata, Crustacea, Amphipoda

Production of Brachycentrus spinae Ross (Trichoptera: Brachycentridae) and its Role in Seston Dynamics of a Southern Appalachian Stream (USA)

Brachycentrus spinae Ross had a univoltine life cycle similar to other Brachycentrus spp. Larvae hatched in May, developed through five instars, and pupated in March. Larval production, excluding silk secretions, was 260.686 mg AFDW m −2 yr −1 , and mean annual standing crop was 40.396 mg AFDW m −2 . Annual and cohort turnover ratios (Production/Biomass) were 6.4 and 6.0, respectively. Case construction (silk + detritus) was estimated at 256.2 mg AFDW m −2 yr −1 . Production attributable to five food types (animal, vascular plant detritus, amorphous detritus, filamentous algae, and diatoms) was calculated using literature derived values for assimilation and net production efficiencies. Animal food accounted for the majority of B. spinae production (61.71%), followed by amorphous detritus (25.08%). Annual food consumption by B. spinae was estimated at 2158.0 mg AFDW m −2 . Seston data from Dryman Fork and B. spinae consumption estimates were used to calculate seston utilization. While larvae ingested only 0.00007% m −2 of total available summer seston, they selectively captured animal material, consuming 3.5 times the amount entering the study section. These data suggested that the animal component of the seston must be replaced every 400 m to support Brachycentrus feeding alone. While this species exerted a minor influence on seston quantity, its selective capture of high quality animal food could significantly alter seston quality.

The Role of Drift Dispersal in Production Ecology of a Stream Mayfly

The role of drift behavior in the production ecology of the mayfly Tricorythodes atratus McDunnough was investigated in a headwater reach of the Mississippi River in northern Minnesota, USA. Comparison of drift and bottom samples revealed that larger nymphs exhibited a greater propensity to drift; in bottom samples, small immatures (1—2 mm) were predominant in a study riffle, whereas larger nymphs (>2 mm) were relatively more abundant in a downstream pool. Annual production was 8.56 g.m—2.yr—1 (dry mass) and the annual turnover ratio (annual production/annual mean biomass) was 26; the species was bivoltine. Errors in production rate estimation resulting from sampling a single habitat were substantial when differential size dispersal of nymphs occurred.

Secondary Production of Epilithic Fauna in a Woodland Stream

Epilithic fauna were sampled by placing three sets of 40 cobbles in transects across a riffle in Factory Brook, Massachusetts. One set was sampled monthly from September 1973 to August 1975, allowing 3 months for recolonization. Three Surber samples were collected concurrently during the last 12 months to provide biomass estimates of infauna. Length-wet weight regression equations and dry weight conversion factors were computed for genera; caloric equivalents were obtained from the literature. Surface area of cobbles was determined by a foil-areagraph technique. Secondary production on cobbles was calculated mainly by genus with the modified Hynes method. Mean standing stock in dry weight (DW) was 0.65 gDW/m2 of cobble surface in 1974 and 0.61 gDW/m2 in 1975. Insect production on cobbles in 1974 was 4.80 gDW/m2-year and 4.32 gDW/m2-year in 1975, or between 22.3-24.7 kcal/m2-year. Approximately half of the mean biomass and production on cobbles was attributed to four genera, Epeorus, Ephemerella, Hydropsyche and Acroneuria. Dipterans constituted 56% of the organisms collected but less than 20% of production; mayflies represented 53% of epilithic production. Annual turnover ratios were 7.4 and 7.1 in 1974 and 1975, respectively, and are a first estimate of community-based P/B for stream benthos in New England. Trophic level production efficiency between primary and secondary consumer groups agreed closely with previous studies on benthic communities in streams and may provide a simplified method for estimating secondary production. Total benthic production on the riffle, based on Surber and cobble sampling, was approximately 12.2 gDW/m2-year.