bluuebunny/crossref_metadata_2025 huggingface dataset:
Defensive larval secretions of leaf beetles attract a specialist predator Parasyrphus nigritarsis
Authors: KÖPF ALFRED , RANK NATHAN , ROININEN HEIKKI , TAHVANAINEN JORMA
Published: November 2003

1. Noxious larval secretions of leaf beetles, which repel generalist predators, do not deter specialist syrphid fly predators (genus Parasyrphus). These flies cause considerable mortality to the beetles, but little is known about their foraging behaviour.

2. Larvae of Parasyrphus nigritarsis were attracted to the volatile larval secretions produced by two prey species Phratora vitellinae and Linaeidea aenea. Parasyrphus nigritarsis feeds on both beetles in nature. Phratora vitellinae feeds on willows and utilizes host plant compounds for secretion production, while the alder‐feeding L. aenea produces an autogenous secretion.

3. Fly larvae were strongly attracted to pieces of filter paper treated with larval secretion of the beetles. They attempted to feed on them for up to 7 min, and were equally attracted to the secretions of Ph. vitellinae and L. aenea. Fly larvae were also attracted to pure salicyl aldehyde, the main component of the secretion of Ph. vitellinae.

4. Fly larvae searched extensively for prey on leaves that had been damaged by beetle larvae. They also followed trails made with solutions containing faecal matter of prey larvae. They showed no differential preference for Ph. vitellinae or L. aenea, but always rejected larvae of the non‐prey leaf beetle Agelastica alni.

5. Beetle secretions thus play an important, but unexpected, role in the feeding behaviour of P. nigritarsis. This predator uses the beetle secretion to locate its prey. The implications of these results for three trophic level interactions are discussed.
HLA‐DR, ‐DQA1 and ‐DQB1 associations in Australian multiple sclerosis patients
Authors: Stewart G. J. , Teutsch S. M. , Castle M. , Heard R. N. S. , Bennetts B. H.
Published: November 2003

Molecular genotyping for the major histocompatibility complex (MHC) class II loci, HLA‐DRB1, ‐DQB1 and ‐DQA1, in 100 patients with relapsing/remitting multiple scerlosis (MS) demonstrated an association with the HLA‐DR2, DQw6‐associated alleles DRB1*1501, DQB1*0602 and DQA1*0102, thereby extending this finding among MS patients in several countries to an Australian population. Analysis by the relative pre‐dispositional effect (RPE) method provided no evidence for a second susceptibility allele at either DQA1 or DQB1. However, our data and that of others suggest a negative association with DQA1*0101. Associations were found with DQB1 alleles sharing sequence homology with DQB1*0602, with DQB1 alleles encoding leucine at residue 26 (Leu 26), with DQA1 alleles encoding glutamine at residue 34 (Gln 34) and with Leu 26 plus Gln 34 alleles, but each was shown by two‐loci linkage analysis to be secondary to the DRB1*1501, DQB1*0602, DQA1*0102 association. The recently reported negative association with DQA1 alleles encoding phenylalanine at amino acid 25, leucine at amino acid 69 and arginine at amino acid 52 was not found in this study, although there was a trend towards reduced phenylalanine at amino acid 25. The determination at a molecular level of an explanation for the world‐wide association with these alleles remains elusive despite major advances in MHC typing.
HLA‐DR/DQ/DP INTERACTIONS IN RHEUMATOID ARTHRITIS
Authors: SEIDL C. , KOCH U. , BRÜNNLER G. , BUHLEIER T. , FRANK R. , MÖLLER B. , MARKERT E. , KOLLER‐WAGNER G. , SEIFRIED E. , KALTWASSER J. P.
Published: November 2003

Rheumatoid arthritis (RA) is associated with the presence of particular HLA‐DRB1 alleles. In order to characterize HLA‐DQB1 and/or ‐DPB1 alleles that contribute to disease susceptibility besides HLA‐DRB1 alleles, we have analysed the HLA‐DRB1, ‐DQB1 and ‐DPB1 polymorphism in 84 RA patients and 135 controls. HLA typing for HLA‐DRB1 and ‐DQB1 alleles was performed using sequence‐specific primers in combination with sequence‐based typing. HLA‐DPB1 alleles were characterized by reverse dot‐blot hybridization. Our data confirm the predominant role of the (Q)R/KRAA sequence from AA position 70–74 of the HLA‐DRB chain for disease susceptibility. In particular, the lysine (K) substitution at position 71 was highly significantly associated with RA. Analysis of the DQB1 locus revealed no association with RA when linkage disequilibrium between HLA‐DRB1 and ‐DQB1 alleles was considered. In contrast, we observed an increased frequency of HLA‐DPB1*0401 among (Q)R/KRAA‐positive patients. (Q)R/KRAA‐negative RA patients exihibited an overrepresentation of HLA‐DPB1*0201 and HLA‐DPB1*0601. Rheumatoid factor (RF) production correlated with the presense of the disease‐associated (Q)R/KRAA amino acid cassette of the HLA‐DRB chain. When HLA‐DPB1 allele frequencies were compared between RF‐positive and RF‐negative RA patients, we observed an increased frequency of HLA‐DPB1*0401 among RF‐positive RA patients and HLA‐DPB1*0201 among RF‐negative patients. These results suggest that besides the predominent role of HLA‐DR molecules in RA, HLA‐DP molecules may have an influence on disease susceptibility and could modulate disease progression. HLA‐DPB1*0401 may function in addition to HLA‐DRB1*04, whereas HLA‐DPB1*0201 and ‐DPB1*0601 may represent additional risk factors among (Q)R/KRAA‐negative RA patients.
GESTATIONAL DIABETES MELLITUS AND HLA CLASS II (‐DQ, ‐DR) ASSOCIATION: THE DIAGEST STUDY
Authors: VAMBERGUE A. , FAJARDY I. , BIANCHI F. , CAZAUBIEL M. , VERIER‐MINE O. , GOEUSSE P. , FONTAINE P. , DANZE P. M. , GROUP THE DIAGEST
Published: November 2003

Gestational diabetes mellitus (GDM) and impaired glucose tolerance during pregnancy (IGT) are associated with an increased risk of perinatal morbidity and then further development of diabetes among 30–50% of affected women. This is a real public health problem that deserves investigation of phenotypic and genotypic predisposing markers. However, the involvement of genetic background in GDM and IGT remains unclear. In particular, association with HLA class II polymorphism has been poorly studied and has produced conflicting results. In attempt to clarify these discrepancies, we investigated HLA class II polymorphism in 95 GDM and 95 IGT women from the north of France using DNA amplification followed by restriction enzyme digestion (PCR‐RFLP). Ninety‐five pregnant women with normal glucose tolerance (NGT) were chosen as a control reference group. The distribution of HLA class II polymorphism was not found to be significantly different between GDM, IGT and NGT samples. In particular, we did not find any significant variation of DRB1*03 and DRB1*04 allele frequencies between these three groups. These data provide further evidence that insulin‐dependent diabetes mellitus (IDDM) HLA class II susceptibility alleles cannot serve as genetic markers for susceptibility to glucose intolerance during pregnancy. However, GDM and IGT were not equivalent to the NGT control group and presented particular HLA patterns. In particular, we observed an increase of the DRB1*0701–DQA1*0201–DQB1*02 haplotype in GDM women (P = 0.02; Pc not significant) and an increase of DRB1*0101–DQA1*0101–DQB1*0501 and DRB1*1302–DQA1*0102–DQB1*0604 haplotypes in the IGT group (P = 0.02 and 8 × 10–3, respectively; Pc not significant). In contrast, we found a decrease in the DRB1*1101 allele in IGT samples (P = 0.03; Pc not significant) and a decrease of DRB1*1103–*1104 alleles in the GDM group (P = 9 × 10–3; Pc not significant). Although these findings are only descriptive, it points out the genetic heterogeneity of glucose intolerance during pregnancy.
Population dynamics of tambaqui, Colossoma macropomum Cuvier, in the Lower Amazon, Brazil
Authors: ISAAC V.J. , RUFFINO M.L.
Published: November 2003

Fishery statistics and length data series for Colossoma macropomum Cuvier obtained during 1992 and 1993 in the Lower Amazon, Brazil were used to describe the fishery and to estimate growth and mortality rates. Mean population parameters were L∞ = 119.85 cm (total length), W∞ = 33.4 kg, K = 0.228 year–1, C = 0.505, Winter Point = July, M = 0.445 year–1, F = 0.94 year–1 and Lc = 28.29 cm. Yield‐per‐recruit analysis showed that an excessive fishing effort and principally a very low length at first capture lead to an increase in overfishing in the region. Corrective measures are recommended.
The 1993 collapse of the Lake Kinneret bleak fishery
Authors: HAMBRIGHT K. D. , SHAPIRO J.
Published: November 2003

Bleak, Acanthobrama terraesanctae Steinitz, constituted an important fishery in Lake Kinneret, Israel, accounting for ≈ 60% of the total commercial harvest, but less than 10% of the total fisheries income for the entire lake. The market demand of 900–1000 t annually has maintained relatively constant harvest pressure since the 1970s. The fishing season of 1992/93 was the last time bleak were harvested commercially. In 1993/94 the fishery collapsed; less than 10% of previous harvests was caught, and most fish were below commercial size. An overview of the bleak fishery during the past 60 years is presented, with evidence indicating that the collapse was the result of two interdependent events relating to harvest‐induced stress: (i) a long‐term shift in harvested fish size (age) that began in 1982; and (ii) two consecutive seasons of overharvest that led to the depletion of 2–3 year classes and the excessive recruitment of young‐of‐year of a single year class.
Stocking experiments using progeny of freshwater‐reconditioned Atlantic salmon, Salmo salar L.
Authors: MOFFETT I.J.J. , KENNEDY G.J.A. , CROZIER W.W.
Published: November 2003

The progeny of salmon, Salmo salar L., kelts reconditioned in fresh water for one and two years were stocked in the spring as swim‐up fry into good salmonid habitat in 1993 and 1994. Survival to the first summer was compared with that of control groups. There was no significant difference (P > 0.4) between the average number of reconditioned kelt and control fry caught per five‐minute semiquantitative electric fishing for the two years. Transformation of semiquantitative electric fishing results showed that average survival rates were about 24% and 30% for reconditioned kelt progeny and their controls, respectively, in 1993, and about 34% for both groups in 1994.
A multivariate model to relate hydrological, chemical and biological parameters to salmonid biomass in Italian Alpine rivers
Authors: ANNONI P. , SACCARDO I. , GENTILI G. , GUZZI L.
Published: November 2003

A multivariate statistical analysis was performed to assess the relationships between a series of river habitat parameters and the variation in salmonid biomass in 13 stations in Italian Alpine salmonid rivers. Various river data were collected and principal component analysis was used to identify the relevant parameters. The best regression model was calculated using two statistics: Mallows’Cp and R2 adjusted for degrees of freedom. The best model only uses six parameters and explained 89% of variation in fish biomass. Various statistical indices were calculated to evaluate model quality and robustness. A sensitivity analysis was carried out to determine how the model slope would change due to independent measurement errors in the parameters. These effects were mostly negligible. This demonstrated that it is possible to simplify habitat quality evaluation using a subset of environmental parameters which should be useful for river management.
Does overfishing lead to a decrease in catches and yields? An example of two West African coastal lagoons
Authors: LAË R.
Published: November 2003

The factors affecting fish yields in lagoons were studied through the stability, species composition and size structure of the yields at high and low fishing intensities, respectively, in Togo and the Ivory Coast. Heavy fishing was followed by the development of a plateau phase resulting from a reorganization of species assemblage. In such a state, exploitation produced only a few dominant species for which average catch lengths were small; which were generally herbivorous and exhibited a continuous reproduction, sometimes a lowering of the age at first sexual maturity, permitting a faster turnover. Even if total catches did not collapse, fish biomass and catch per unit effort decreased when fishing effort increased. One option for management could be to locate the level of fishing effort on the plateau such that fishermen can be at least financially independent and provide sufficient fish for local subsistence.
Potential yield estimates of unexploited pelagic fish stocks in Lake Malawi
Authors: THOMPSON A.B. , ALLISON E.H.
Published: November 2003

The biomass of the offshore pelagic fish of Lake Malawi was estimated at 168 400 t and is currently unexploited by a fishery. This biomass comprises, by weight, 81% Cichlidae, 15% catfish and 4% Cyprinidae. A Beverton and Holt dynamic pool model was used to estimate potential sustainable yields and to forecast likely changes to the size and age structure of the fish populations under various levels of fishing effort. The total sustainable yield from the offshore fish population was estimated at 34 000 t yr–1 and, if harvested, would almost double the yield of fish from the lake. Potential yields on an areal basis are low (14.2 kg ha–1 yr–1), but are consistent with expectations from studies of pelagic ecosystem productivity.
A review of the offshore trawl fishery for crustaceans on the east coast of South Africa
Authors: FENNESSY S.T. , GROENEVELD J.C.
Published: November 2003

This paper reviews current knowledge on the trawl fishery for crustaceans on the east coast of South Africa. The shallow water fishery targets penaeid prawns, particularly Penaeus indicus Milne‐Edwards, while the deep water fishery targets pink prawns, Haliporoides triarthrus Stebbing, langoustines, Metanephrops mozambicus (Jenkins), and rock lobster, Palinurus delagoae, Barnard. Between 1988 and 1993, annual catches of targeted species averaged about 350 t. There was a total bycatch of about 1700 t per annum, most of which was discarded. Retained bycatch was dominated by the red crab, Chaceon macphersoni, as well as fish and cephalopods. Although trawling effort declined during the period under review, this trend has recently reversed.
Vulnerability‐size effects of electric fishing on population estimate, size distribution and mean weight of a sea trout, Salmo trutta L., stock
Authors: KRISTIANSEN H.R.
Published: November 2003

A dynamic mark‐recapture electric fishing study on sea trout, Salmo trutta L., was carried out from July 1989 to January 1990. There was a significant difference in the recapture probability (P = R/M) between small (24–39 cm) and large (40–84 cm) sea trout with P‐values of 0.31 and 0.62, respectively (χ2 = 16.52, P < 0.001). The vulnerability‐size relationship resulted in a slight overestimation of population size (2.5%) using the Petersen method by adding the two size classes together in the computations. Separate computations for the two size classes had no significant effect upon the estimate of the seasonal length distributions but a significant effect on the estimates of total length distribution (P < 0.001) and the mean weight of the mature stock (P < 0.001). The present data emphasises that size‐selectivity should be taken into account in electric fishing studies on adult sea trout.
Catch per unit effort trends in the coastal fishery of Manzanillo, Colima, Mexico
Authors: ESPINO‐BARR E. , MACíAS‐ZAMORA R. , CRUZ‐ROMERO M. , GARCIA‐BOA A.
Published: November 2003

The catch per unit effort (CPUE) values, expressed as kg trip–1 in a coastal fishery, were considered to be an index of resource abundance to explain changes through time. The trends in catch and effort for three commercial landing sites in Manzanillo and Santiago Bays in Colima, Mexico, were analysed for the period November 1982 to May 1991. The CPUE data were analysed using the spectral method, which showed four harmonic periods of 38.53, 13.64, 9.29 and 6.26 months. To explain these variations, sea surface temperature (SST) was used as an indicator of environmental change. Two harmonic components were identified, with periods of 12.5 and 39.0 months each, which coincided with two of the periods found in the CPUE series. Once these harmonics, which were considered anomalous to the fishing effort, were subtracted a constant CPUE throughout the study period was found. It was concluded that in the CPUE series, the most influential component corresponded to a lapse of 38.53 months, suggesting a possible link with the ‘El Niño’ phenomenon. However, in the temperature series, the most important component was represented by a value of 11.95 months, which is believed to be associated with changes in the environment.
Effects on sediments and biota of cleaning a salmonid spawning channel
Authors: MUNDIE J.H. , CRABTREE D.G.
Published: November 2003

Prior to the cleaning of the Little Qualicum chum salmon channel, the sediments, of which 33% were greater than 64 μm, were distributed fairly evenly throughout the 56 cm gravel column and occupied 25% of the interstitial space. Filamentous algae, especially Didymosphenia, were abundant in summer and reduced the diversity of the zoobenthos relative to that of the parent stream. The mean number of salmonid food‐organisms was 30 000 m–2 (sampled with a 200 μm net); 57% were Chironomidae at the upstream end of the channel, increasing to 93% at the downstream end. Numbers of coho salmon fry, Oncorhynchus kisutch, km–1 of channel exceeded those of productive natural streams. Scarification of the channel resulted in removal of 88% of the sediments, reduction of arthropods by 98%, and reduction of emerging insects by 88% across the centre of the channel and by 90% at the margins. Coho salmon fry showed no significant mortalities during cleaning and lived on marginal aquatic insects until the channel was re‐colonized 8 weeks later.
What is the value of a wild salmon smolt, Salmo salar L.?
Authors: KENNEDY G.J.A. , CROZIER W.W.
Published: November 2003

Information on marine and freshwater survival and exploitation of River Bush salmon was developed into a model illustrating the potential ranges of grilse production per 1000 smolts. Values were attributed to the grilse ‘crop’ at each of three potential production stages – commercial landings, angler catches and fertilized egg production – using both published and derived valuations. Using the model, a range of values per wild smolt was calculated for grilse production on the River Bush.
Vertical distribution of planktivorous 0+ pikeperch, Stizostedion lucioperca (L.), in relation to particulate or filter feeding
Authors: FRANKIEWICZ P. , ZALEWSKI M. , SCHIEMER F. , DABROWSKI K.
Published: November 2003

The main prey of 0+ pikeperch in the pelagic zone of the Sulejow Reservoir was Leptodora kindtii and copepods, which together constituted only about 20% of the zooplankton by number in the water. Leptodora kindtii predominated in pikeperch food close to the surface, and copepods in deeper water. A depth‐dependent shift in feeding mode from large particle selection to filtering, as an adaptation to reduce intraspecific competition and avoid predatory pressure in the upper part of the water column, was suggested. Specimens with less stomach content were observed more frequently closer to the surface. They were exposed to heavy predation from adult conspecifics, which prevented them from foraging efficiently, although they were able to feed on larger zooplankton because of better penetration by moonlight.
Changes in the density of introduced bullhead, Cottus gobio L., and its impact on juvenile Atlantic salmon, Salmo salar L., densities in a sub‐Arctic salmon river in northern Finland
Authors: PIHLAJA O. , JULKUNEN M. , NIEMELÄ E. , ERKINARO J.
Published: November 2003

A newly introduced species, the bullhead, Cottus gobio L., was observed for the first time in the River Utsjoki, a tributary of the River Teno, in 1979. The River Teno is one of the most important Atlantic salmon, Salmo salar L., rivers in Northern Europe and its tributary the River Utsjoki is an important salmon spawning and nursery area. The densities of bullhead were lowest in the areas to which the species has spread most recently and highest in the areas downstream of its introduction point. Densities were markedly lower upstream. Statistical analysis showed that the presence of the bullhead had not affected juvenile salmon densities in the River Utsjoki.
Migration of albacore, Thunnus alalunga, in the North Pacific Ocean in relation to large oceanic phenomena
Authors: KIMURA SHINGO , SUGIMOTO MUNENORI NAKAI AND TAKASHIGE
Published: November 2003

On the basis of Japanese long‐line fishery data during 1970–1988, anticlockwise migration routes of albacore in the North Pacific are newly proposed. The annual migration route for mature albacore is described as a closed ellipse with a centre at 20°N and 170°E, and is wider in El Niño years than non‐El Niño years associated with an appearance of a cold‐water region in the central and south‐western North Pacific. Immature albacore also have an anticlockwise migration route in winter which extends from 25°N to 35°N and from 130°E to 180°E, when the Kuroshio has a relatively straight path. However, the migration does not persist when the Kuroshio takes a large meander path.
The demography of Calanus pacificus during winter–spring Californian El Niño conditions, 1992–1993: implications for anchovy?
Authors: MULLIN MICHAEL
Published: November 2003

Samples from the southern California sector of the California Current System were examined to test for changes in abundance, reproduction, recruitment and naupliar survival of the planktonic copepod, Calanus pacificus, coincident with the 1993 Californian El␣Niño, relative to 1992 (also El Niño conditions) and to 1989–1991 (defined as `normal'). In 1993, as in 1992, females were rare in both winter and spring, but per capita reproduction was less, food limitation was greater and biomass of chlorophyll was reduced only in winter. Recruitment was more variable than was naupliar survival. Recruitment increased in both El Niño springs, but survival of older naupliar stages decreased. The mesoscale distributions of larval anchovy, relative to eggs and nauplii of Calanus, did not result in efficient use of the reduced supply of this source of food, and the abundance of larval anchovy did not cause measurable variation in the survival of naupliar Calanus.
Oceanographic variability and changes in Antarctic krill (Euphausia superba) abundance at South Georgia
Authors: Trathan P. N. , Brierley A. S. , Brandon M. A. , Bone D. G. , Goss C. , Grant S. A. , Murphy E. J. , Watkins J. L.
Published: November 2003

Oceanographic data collected to the north of South Georgia were examined for three consecutive summers (1996/97, 1997/98, 1998/99). The results show the existence of a shelf break front during each period. The most reliable means of defining the front was the potential density anomaly at the near‐surface potential temperature minimum. In each year, off‐shelf waters were separated from on‐shelf waters by water with a potential density anomaly between 27.22 and 27.29 kg m−3. During 1997/98, the near‐surface potential temperature minimum was much colder and much shallower than in other years and was consistent with waters originating from much further south than South Georgia; these differences were further evident at a single deep off‐shelf station. The oceanographic changes during 1997/98 were consistent with a mesoscale or large‐scale movement of the southern Antarctic Circumpolar Current front.

Acoustically determined densities of Antarctic krill, Euphausia superba, at South Georgia showed consistent patterns between years. Densities were substantially higher over the shelf compared with off‐shelf, with the highest densities at the shelf edge; densities were also higher to the east of the island. During 1997/98, acoustic densities of krill were substantially higher than in other years. The coincidence of the elevated acoustic density and the cooler oceanographic conditions was explored. When data from all years were combined and analysed by Generalized Additive Model, an inverse relationship between acoustic density and temperature was apparent. Historical data were also examined and it was noted that the only other occurrence of such a high estimate of krill density at South Georgia, was when oceanographic conditions were also colder.
Atmospheric deposition of sulphur and nitrogen species in the U.K.
Authors: CAMPBELL GlENN , LEE DAVID
Published: November 2003

1. The foundations of our understanding of acid deposition were laid in the last century, but the scale and scope of damage to sensitive receptors has only been subject to intensive investigation over the last 30 years or so. Negotiations are now well underway to reduce emissions, and for some pollutants policy is in place, so that these receptors may be protected adequately. Crucial to this has been the ‘critical loads’ approach adopted in the U.K. and elsewhere in Europe over the last 6 years.

2. This paper describes the source of acidic emissions, how these emissions are transformed in the atmosphere and subsequently deposited. Measurements of wet deposition are made at a number of sites in the U.K. and some of the results from the networks are presented. These results allow wet and dry deposition to be mapped and the methodologies and underlying assumptions to these procedures are described, and S deposition has been estimated for the U.K. Acid Waters Monitoring Network sites.
The energetic importance of terrestrial arthropod inputs to three warm‐water streams
Authors: CLOE III WILLIAM , GARMAN GREG
Published: November 2003

1. Inputs of terrestrial arthropods (number and mass m–2 d–1) from riparian corridors to three streams representing different orders were highly variable among seasons and sites, with significantly greater (P < 0.05) inputs at the headwater stream during summer months, compared with other sites and seasons.

2. No significant differences in estimates of stream retention of terrestrial arthropods (number and mass m–2 d–1) were observed among sites; however, retention of terrestrial arthropods at all sites was significantly greater during summer months, compared with other periods.

3. The gravimetric proportion of terrestrial arthropods present in the stomachs of redbreast sunfish (Lepomis auritus) and bluegill (L. macrochirus) was equivalent among sites. However, estimates of the dietary importance of terrestrial arthropods at all study sites were significantly greater in the summer, compared with other seasons.

4. Estimates of the potential annual energetic contribution (kJ m–2 d–1) of terrestrial arthropod inputs to the stream system were comparable with published rates of total annual production of aquatic macroinvertebrates in other Virginia headwater streams.

5. Results of this study supported the hypothesis that terrestrial arthropods represented an important energetic subsidy to stream fish during periods of low aquatic macroinvertebrate availability, and suggest that this component of allochthonous input is a potentially significant, but poorly understood energetic linkage between riparian landscapes and stream ecosystems.
Reconstructing the past density of planktivorous fish and trophic structure from sedimentary zooplankton fossils: a surface sediment calibration data set from shallow lakes
Authors: JEPPESEN ERIK , MADSEN ESBEN AGERBO , JENSEN JENS PEDER , ANDERSON N.
Published: November 2003

1. As quantitative information on historical changes in fish community structure is difficult to obtain directly from fish remains in lake sediments, transfer function for planktivorous fish abundance has been developed based on zooplankton remains in surface sediment (upper 1 cm). The transfer function was derived using weighted average regression and calibration against contemporary data on planktivorous fish catch per unit effort (PF‐CPUE) in multiple mesh size gill nets. Zooplankton remains were chosen because zooplankton community structure in lakes is highly sensitive to changes in fish predation pressure. The calibration data set consisted of thirty lakes differing in PF‐CPUE (range 18–369 fish net–1), epilimnion total phosphorus (range 0.025–1.28 mg P l–1) and submerged macrophyte coverage (0–57%).

2. Correlation of log‐transformed PF‐CPUE, total phosphorus and submerged macrophyte coverage v the percentage abundance in the sediment of the dominant cladocerans and rotifers revealed that the typical pelagic species correlated most highly to PF‐CPUE, while the littoral species correlated most highly to submerged macrophyte coverage. Consequently, only pelagic species were taken into consideration when establishing the fish transfer function.

3. Canonical correspondence analysis (CCA) revealed that the pelagic zooplankton assemblage was highly significantly related to PF‐CPUE (axis 1), whereas the influence of total phosphorus and submerged macrophyte coverage was insignificant. Predicted PF‐CPUE based on weighted average regression without (WA) and with (WA(tol)) downweighting of zooplankton species tolerance correlated significantly with the observed values (r2 = 0.64 and 0.60 and RMSE = 0.54 and 0.56, respectively). A marginally better relationship (r2 = 0.67) was obtained using WA maximum likelihood estimated optima and tolerance.

4. It is now possible, quantitatively, to reconstruct the historical development in planktivorous fish abundance based on zooplankton fossil records. As good relationships exist between contemporary PF‐CPUE data and indicators such as the zooplankton/phytoplankton biomass ratio, Secchi depth and the maximum depth distribution of submerged macrophytes, it is now also possible to derive information on past changes in lake water quality and trophic structure. It will probably prove possible further to improve the transfer function by including other invertebrate remains, e.g. chironomids, Chaoborus, snails, etc., and its scope could be widened by including deeper lakes, more oligotrophic lakes, more acidic lakes and lakes with extensive submerged macrophyte coverage (in the latter case to enable use of the information in the fossil record on plant‐associated cladocerans).
Inferring the minimum pH of streams from macroinvertebrates using weighted averaging regression and calibration
Authors: HÄMÄLÄINEN HEIKKI , HUTTUNEN PERTTI
Published: November 2003

1. Data on macroinvertebrates and stream chemistry were collected from sixty‐four streams in Finland. Weighted averaging (WA) regression and calibration models were constructed to infer the minimum pH of streams from their invertebrate assemblages. The purpose was to develop an instrument for biological assessment and monitoring of stream acidification. The WA method was compared with simpler approaches, based on qualitative invertebrate data and pH tolerance limits, that are widely used.

2. Performance of the two approaches was assessed in terms of correlation between the inferred and observed minimum pH within the ‘training set’, and in terms of root mean squared differences (predicted – observed) (RMSEP) estimated by cross‐validation or bootstrap resampling techniques. The models were further tested using independent data from the literature representative of a wide geographical range.

3. The predictive power of the WA models was reasonable (RMSEP 0.40–0.44 pH units) in the training set and consistently better than that of the tolerance limit method. In contrast to the latter, the WA models were able to infer a minimum pH above 5.5, suggesting they could detect the early stages of acidification.

4. The WA models performed better than the tolerance limit method in inferring pH from the independent literature, further demonstrating the superiority and generality of the WA approach.

5. The weighted averaging technique could be an effective and widely applicable tool for contemporary biological monitoring and assessment using aquatic invertebrates.
Do simultaneous hermaphrodites choose their mates? Effects of body size in a planarian flatworm
Authors: PETERS ANNE , MICHIELS NICOLAAS
Published: November 2003

1. We tested whether or not the simultaneous hermaphrodite Dugesia polychroa mates randomly with respect to partner size, a strong indicator of female fecundity.

2. The number and duration of copulations were recorded in forty‐eight pairs over 5 days. To minimize effects of individual differences in copulatory activity, all animals were each tested twice: once with an equally large partner (n = 24 equal‐sized pairs) and once with a partner of different size (smaller or larger, respectively, ratio 1 : 1.5,

n = 24 unequal‐sized pairs).

3. The animals copulated frequently. No significant differences were observed between treatments in the number of pairs that copulated. Mating behaviour of equal‐sized and unequal‐sized pairs was compared in a pair‐wise analysis. Latency to the first copulation and the average number of copulations did not differ when mating with an equal‐ or unequal‐sized partner. Average copulation duration increased with increasing size in equal‐sized pairs, but not in unequal‐sized pairs.

4. In an additional experiment, where three large and three small animals were combined (three replicates) and observed for 1–3 days, the mating pattern did not differ from random mating by size.

5. Our data indicate that in D. polychroa the decision to mate is essentially random with respect to size. We argue that this is not caused by, for example, high costs of mate searching, but that simultaneous hermaphrodites with reciprocal insemination mate indiscriminately when (i) matings are easy to obtain and (ii) the cost of mating is low or compensated for by sperm digestion.
Modelling of underwater light in freshwater lakes using survival and failure time analysis
Authors: RØRSLETT BJØRN
Published: November 2003

1. This study presents a new approach to modelling subsurface irradiance using concepts from survival and failure time analysis. The model applies a modified Weibull distribution function to predict downwelling irradiance. Data sets from forty‐seven Norwegian sites show extremely high coefficients of determination, up to 99.99%, when analysed by the Weibull model.

2. The uncritical use of a single kd value to model underwater light conditions is likely to result in poor estimates of received irradiance. This error may amount to several hundred per cent. The practice of force‐fitting linear least‐squares regressions to log‐transformed irradiance data inevitably leads to highly biased estimates of the true fraction of incident irradiance entering the water.

3. Wave effects causing fluctuations of subsurface irradiance are modelled with synthetic data and compared with field observations. Fluctuations of surface elevation by waves produce skewed frequency distributions of the underwater light field. The result of these effects, which are to reduce the accuracy of estimated model parameters, can be largely eliminated by carefully designing field procedures used for the acquisition of subsurface light data.
Environmental variation and behaviour: resource availability during ontogeny and feeding performance in salamander larvae (Ambystoma texanum)
Authors: MAURER ERIC
Published: November 2003

1. The effects of resource availability during ontogeny on subsequent feeding performance were investigated in larvae of the small‐mouthed salamander (Ambystoma texanum).

2. Salamander larvae were reared individually in either high or low prey density treatments for 7 weeks prior to intermediate prey density foraging trials. Larvae from the low prey density treatment were on average 35% smaller in body size than individuals from the high prey density treatment.

3. Resource availability during development influenced larval feeding rates and altered the relationship between body size and three feeding performance measures (attack rates, capture success and feeding rates). Feeding rates in predation trials were also positively correlated with growth rate early in the larval period (until the end of week 5).

4. These results suggest that the environment to which developing organisms are exposed can have significant effects on subsequent behaviour, and that small‐mouthed salamander larvae may show state‐dependent changes in feeding behaviour in response to differences in long‐term feeding history. Additionally, differences in feeding performance may influence the probability of survival to the adult stage for organisms that utilize ephemeral habitats.
Seasonal dynamics of the planktonic community in Lake Druzhby, Princess Elizabeth Land, Eastern Antarctica
Authors: LAYBOURN‐PARRY JOHANNA , BAYLISS PETER
Published: November 2003

1. The temporal abundance and composition of the plankton of a continental Antarctic lake (Lake Druzhby) situated in the Vestfold Hills, Eastern Antarctica was investigated from December 1992 to December 1993. The system was dominated by microbial plankton (cyanobacteria, heterotrophic bacteria and protozoans) with few metazoans.

2. Chlorophyll a concentrations ranged between 0.15 and 1.1 μg l–1 and showed highest levels from late winter to spring.

3. Heterotrophic bacteria ranged between 75 and 250 × 106 l–1 with highest abundances in late winter/spring. Mean bacterial biovolumes showed considerable seasonal variation (0.05–0.31 μm3). Largest biovolumes occurred in summer and this was the time of highest community biomass.

4. Heterotrophic nanoflagellates reached highest abundances in late summer (maximum 14 × 105 l–1). Their mean biovolume also exhibited considerable seasonal variation, ranging between 1.77 and 27.0 μm3, with largest size resulting in community biomass peaking in early summer. Ciliated protozoa were poorly represented and sparse. Phototrophic nanoflagellates were sparse in this lake; instead the phototrophic plankton was dominated by a small rod‐shaped cyanobacterium which constituted the largest carbon pool in the system. It was common throughout the year, its biomass peaking in autumn. Its presence is discussed in relation to lake morphometry and light climate.

5. Heterotrophic flagellate grazing rates ranged from 6.78 bacteria cell–1 day–1 at 2 °C to 11.8 bacteria cell–1 day–1 at 4 °C. They remove around 2% of the bacterial carbon pool per day during summer and winter.

6. Nutrient levels were low and recorded in pulses. Dissolved and particulate organic carbon were also low, usually less than 3 mg l–1 and 600 μg l–1, respectively. The carbon pools were derived from autochthonous sources. This lake system is driven by bottom‐up forces and lacks top‐down control, which fits into the picture currently seen for continental Antarctic lakes.
The ecology of a subterranean isopod, Caecidotea tridentata
Authors: EDLER C. , DODDS W.K.
Published: November 2003

1. The blind isopod Caecidotea tridentata is the dominant invertebrate in a simple community of subterranean organisms inhabiting the local, shallow aquifer under Konza Prairie, Kansas, U.S.A.

2. The ecology of this karst aquifer was explored by sieving water from a spring, collecting water samples for analysis, and manipulating sediments and invertebrates in the laboratory. The size frequency distribution was stable and gravid females were present throughout the year, suggesting continuous reproduction.

3. The number of isopods collected per litre was negatively correlated with discharge and the abundance of bacteria, but positively related to the numbers of an amphipod (Bactrurus hubrichti). This may be explained if both the isopods and the amphipods track the saturated zone below the top of the water table; at lower discharge, the top of the water table is closer to the spring outlet. The suspended bacteria wash out in greater numbers with high discharge.

4. When isopods and carbon were added in a pairwise experimental design to sediments collected from the aquifer, the isopods significantly stimulated numbers and activity of planktonic and sedimentary bacteria, while carbon had no effect. This suggests that invertebrates can affect the microbes locally in an aquifer.
Responses of the predatory rotifer Asplanchna intermedia to prey species differing in vulnerability: laboratory and field studies
Authors: IYER NANDINI , RAO T.
Published: November 2003

1. We have studied the numerical and functional responses of campanulate morphs of Asplanchna intermedia fed five species of rotifer (Brachionus rubens, B. patulus, B. calyciflorus, Hexarthra mira and Filinia longiseta). The vulnerability of the prey varied with their morphology and mode of swimming.

2. To test the numerical and functional responses, prey species differing in their morphology and mode of swimming were provided. Responses were also tested with mixtures of evasive and non‐evasive prey provided in three different ratios.

3. A. intermedia showed a type II functional response to all the prey species provided.

4. The population growth rate of A. intermedia on the various prey species provided ranged from a minimum of –0.24 to a maximum of 0.68. There was a significant correlation between the capturability of a prey species and the population growth rate of the predator feeding on it. The capturability of a prey species also has a significant influence on the maximal predator density but not on the time taken to reach it.

5. Observations from a field study undertaken over a 10‐month period to study the prey preferences of A. intermedia in nature were corroborated by the laboratory findings.
A multivariate analysis of phytoplankton and food web changes in a shallow biomanipulated lake
Authors: ROMO SUSANA , VAN DONK ELLEN , GYLSTRA RONALD , GULATI RAMESH
Published: November 2003

1. Phytoplankton dynamics, food chain changes and resilience in Lake Zwemlust, a shallow lake in The Netherlands, are described for the period 1986–94.

2. After biomanipulation in 1987, the lake moved through two alternative states, while the external nutrient loadings were maintained. A clear‐water phase, mostly dominated by macrophytes, persisted from 1987 to 1991, and a rather turbid state, dominated by algae, occurred in the summers of 1992–94, after several consecutive and sustained perturbations affecting different parts of the food web in the lake. These two periods were characterized by different community structures.

3. The phytoplankton assemblage gradually changed in a pattern that reverted in later years towards that of the pre‐biomanipulation stage, although the same species composition was not regained. This agrees with some mathematical models. During the clear‐water phase, nutrient shortage, light climate and zooplankton feeding selected in favour of small, high surface : volume ratio and rapidly reproducing algae. However, in mid‐summer of 1992–94, nutrient availability and cladoceran grazing on edible algae favoured cyanophytes.

4. Nutrients were transferred to higher trophic levels or lost from the system at relatively high rates when the lake was in a piscivore–macrophyte‐dominated state, while they tended to accumulate in the algae in a planktivore‐dominated chain without macrophytes. The role of weed beds was central for nutrient competition (mostly nitrogen) with algae, as well as a refuge and a base for alternative food sources to grazers. Weed beds seemed to have a strong effect in increasing connectedness, resilience and stability of the lake community.

5. The complete return of Zwemlust to a turbid state dominated by phytoplankton seems to have depended upon turnover of the limiting nutrient, which was retarded by macrophytes and stimulated by planktivorous fish and waterfowl.
Epiphytes from a deep‐water characean meadow in an oligotrophic New Zealand lake: species composition, biomass and photosynthesis
Authors: HAWES IAN , SCHWARZ ANNE‐MAREE
Published: November 2003

1. The epiphytic flora of a characean meadow in Lake Coleridge, a deep, oligotrophic lake on the South Island of New Zealand, was dominated by diatoms, particularly Eunotia pectinalis and Achnanthes minutissima. The meadows occupied a depth range from 5 to 30 m. Adnate taxa predominated at all depths below 5 m, while increased taxonomic diversity at 5 m resulted from an increased abundance of erect taxa, including chlorophytes and stalked diatoms.

2. Seasonal changes in epiphyte biomass were followed using artificial substrata and by estimating epiphyte chlorophyll a concentration on host plants. The latter required development of a novel technique utilizing the consistent relationship between fucoxanthin and chlorophyll a concentrations in the epiphyton. Epiphyte chlorophyll a on host plants varied with depth and host species between 0.1 and 0.3 mg g–1 dry weight. Maximum epiphyte biomass was at 10–15 m depth. At depths of 15 m and less, epiphyte chlorophyll a reached a maximum of ≈ 200–300 mg m–2 in mid‐summer, while at greater depths maximum biomass was less and coincided with a period of clear water in spring.

3. Photosynthetic carbon fixation was estimated from photosynthesis–radiation curves and estimates of radiation flux at sampling depths. At depths greater than 10 m, variability of the vertical extinction coefficient of lake water rather than seasonal fluctuations in incident radiation were responsible for determining the temporal pattern of production. Chlorophyll a‐specific photosynthesis was estimated to peak in summer at 5 m (8 mg mg–1 day–1), and in spring at all other depths.

4. Annual epiphyte production was estimated as 27 g C m–2 year–1 at 5 m depth, falling to 15 g C m–2 year–1 at 15 m and 1 g C m–2 year–1 at 30 m. Areal biomass changes tended to be temporally but not quantitatively coupled to estimated in situ photosynthesis, and we hypothesize that epiphyte biomass may have been controlled by grazing gastropod snails.
Scales of observation of riparian forests and distributions of suspended detritus in a prairie river
Authors: JOHNSON SHERRI , COVICH ALAN
Published: November 2003

1. Detrital inputs from riparian forests can provide the main source of energy to aquatic consumers in stream communities. However, the supply of coarse organic detritus to stream communities is difficult to predict. Patchy riparian inputs and connectivity between reaches have complicated studies and disrupted patterns of the distribution of suspended coarse particulate organic matter within streams and rivers.

2. In this study we emphasize the importance of spatial and temporal scales in determining potential distribution of instream leaf litter. Although large pulses of detritus are transported by streams during storm flows, the main supply of benthic leaf litter used by shredders and of suspended particulate organic matter used by filter feeders is transported during prolonged periods of baseflow. The local, fine‐scale distribution of this organic matter is determined by the location and continuity of leaf litter sources (riparian vegetation) and specific features of channel roughness (such as woody debris, roots and rocks).

3. Viewing riparian vegetation at several scales results in variable conclusions regarding the amount of potential source area of leaf detritus. The percentage of suspended whole leaves at sites in the Little Washita River, Oklahoma, U.S.A. was best explained by the percentage of riparian forest cover in 500 m and 1000 m reaches upstream of the sites, as viewed by remote sensing imagery. The amount of leaf fragments was best explained by distance downstream along the longitudinal gradient. Ash‐free dry mass of suspended coarse particulate matter did not correlate with any measures of riparian cover.

4. Our results suggest that leaves originate over longer reach lengths than those generally considered as source areas. Scale is an important consideration in studies of riparian patterns and related instream processes because of the need to integrate point dynamics as well as upstream influences.