Short-term thermal acclimation induces adaptive changes in the inner mitochondrial membranes of fish skeletal muscle

In the oxidative muscles (musculi laterales superficiales) of crucian carp Carassius carassius acclimated for 6 weeks to either 5 or 25° C, the volume density and the surface density of fibres per tissue did not differ significantly between the control and experimental groups. The correlation ratio (μ²) for these values was below 50, 39·3 and 43·9 respectively. After acclimation to 5° C, the surface density of outer mitochondrial membrane per fibre increased significantly from 0·93 to 1·23m² cm⁻³ in the summer population but dropped from 0·94 to 0·67 m² cm⁻³ in the winter population. The surface density of outer mitochondrial membrane per mitochondrion increased from 3·24 to 4·52 m² cm⁻³ in summer fish. After acclimation to 25° C, the surface density of inner mitochondrial membranes per muscle fibre decreased from 4·04 to 1·79 m² cm⁻³ in summer fish and from 3·86 to 1·07 m² cm⁻³ in winter fish. The surface density of inner mitochondrial membranes per mitochondrion increased from 14·17 to 15·60 m²cm⁻³ in summer fish but dropped from 13·91 to 10·67 m² cm⁻³ in winter fish. Correlation matrices demonstrate a negative correlation of the surface density of outer mitochondrial membrane per mitochondrion with the volume density of mitochondria per fibre and temperature, suggesting cold-induced proliferation of small mitochondria. It was concluded that short-term cold acclimation increased surface area of the inner mitochondrial membranes in summer fish.     

Fish production in Oued Sebaou, a seasonal river in North Algeria

Fish were sampled by electrofishing at three contiguous sites 26 km from the source of Oued Sebaou, a seasonal river in North Algeria. River discharge ranges from 300 m³s⁻¹ in the peak of the rainy season to 0.1 m³s⁻¹ at the end of the dry season. Extensive gravel extraction from the river bed takes place during the dry season.
Two species were recorded at each site: Barbus callensis , which is heavily fished locally, and Anguilla anguilla . The three sample maximum likelihood Zippin method was used to estimate mean density and standing crops, which were: barbel, 452 fish ha⁻¹, 5.33 kg ha⁻¹; eels, 149 fish ha⁻¹, 3.04 kg ha⁻¹. Estimated average biomass and production were: barbel, 2.31 kg ha⁻¹, 4.27 kg ha⁻¹ year⁻¹; eels, 1.51 kg ha⁻¹, 2.60 kg ha⁻¹ year⁻¹.     

Influence of water depth on dispersion of juvenile salmonids, Salmo salar L. and S. trutta L., in a Scottish stream

The dispersion of salmon and trout of 0 +, 1 + and 2 + age classes was examined by electrofishing 12 sections of a stream in Perthshire, Scotland at the end of the growing season in September to October in 1972 and 1976. In 1972 sections ranged in surface area from 21 to 122 m² and had volumes of 5.0–17.3 m³ and when surveyed in 1976 surface areas were 15–106 m² and volumes 2.1–6.7 m³. In 1976 widths and areas of sections were 63–87% of the values for 1972, depths were 39–68% and volumes 28–52% of the earlier values. These differences were due to 1976 being drier and warmer. In both years, all sections contained 0 + and 1 + age classes of salmon and trout and some sections contained 2 + age salmon and trout. The total density of fish in a section ranged from 1.9 to 3.9 m⁻² in 1972 and from 3.72 to 6.08 m⁻² in 1976. There was an inverse relationship, significant in 1972 only, between the density of 0 + salmon and that of 1 + trout in the different sections. Densities of both 0 + and 1 + salmon in the sections were inversely correlated, and those of 0 + and 1 + trout were directly correlated, with area of water deeper than 10 cm.     

Seasonal activities of Barbus barbus: effect of temperature on time-budgeting

Surgically implanted activity-circuit radio transmitters (40 MHz) were used to study the seasonal activities of 21 adult (males: 23 to 35 cm f.l. and females 38 to 55 cm f.l. ) Barbus barbus (Pisces, Cyprinidae) in the River Ourthe (Southern Belgium) in 1989–1991. During the autumnal thermal transition (water temperature 9 to 10° C), the typical dusk and dawn pattern observed in summer turned to a trimodal pattern with the emergence of a diurnal phase. The auroral then crepuscular and finally diurnal activity periods progressively vanished as water temperature decreased down to the thermal limit for activity (4.0° C), when barbel entered a dormancy period. An opposite progressive shift was observed during the spring thermal transition. Daily activity budgets ranged from 0 to 720 min—on the annual cycle and were significantly ( r ²=0.686, P <0.05, d.f. = 36) dependent on water temperature and on morphodynamic unit size, while fish size was non-significant. Although the dusk and dawn rhythm pattern was consistent throughout summer, water temperature significantly ( P <0.05) interfered with the respective duration of crepuscular and auroral activities ( r ²=0.586, d.f. = 57 and r ²=0.692, d.f. = 55). The precise timing of activities was also thermal-related and the activities of small male barbel were proportionally more nocturnal than those of large female barbel (ANCOVA, F =80.61, d.f. = 31 and F =4.s5, d.f. = 23, at dusk and dawn respectively), possibly due to predation pressure on small fish. It is concluded that the seasonal variations of activity budgets, rhythm patterns and timings in B. barbus correspond to a form of time-budgeting partly to achieve thermal homeostasis in a variable environment.     

Rare and asymmetrical hybridization of the endemic Barbus carpathicus with its widespread congener Barbus barbus

In endemic species that co-occur with widespread congeners, hybridization can lead to an influx of novel and beneficial genetic variation, but high rates of introgression may cause genetic swamping of the endemic species and have detrimental effects on its survival potential. This study examines hybridization between sympatric populations of the Carpathian barbel Barbus carpathicus , a recently discovered cryptic species with a restricted range, and the widespread common barbel Barbus barbus . Based on six diagnostic allozyme loci, a microsatellite locus and mtDNA, hybrids were found to be present at multiple localities within the Vistula River drainage (Baltic Sea) as well as in the Tisza River system of the Danube River drainage (Black Sea). However, the numbers of hybrids were very low; four individuals of 230 fish sampled from the Vistula drainage. Bayesian assessment of their nuclear genotypes suggested that two hybrids in the Vistula drainage and nine in the Tisza system were F₁ generation, and one in the Vistula drainage and one in the Tisza system were backcrosses (BC) to B. barbus , while no F₂ or BC to B. carpathicus were detected. No hybrid carried B. carpathicus mtDNA and cytonuclear linkage disequilibria showed significant positive associations between hybrid genotypes and B. barbus mtDNA, suggesting unidirectionality in the interspecific mating with a disproportionate contribution of B. barbus mothers. Despite geographically broad occurrence of hybrids, these data provide evidence of strong constraints on hybridization in the native breeding habitats and the lack of introgression towards B. carpathicus .     

Fish production in the Jarama River, Central Spain

Fish production was estimated at three sites on the Jarama River, a small, typical upland river in Central Spain. Population estimates were made by the successive removal method of electrofishing. The same six species were recorded at each of the sites: Chondrostoma polylepis, Barbus barbus bocagei, Leuciscus cephalus pyraenaicus, Salmo trutta m. fario, Gobio gobio and Cobitis paludicola , with the first three species always dominant. Density, biomass, production (assuming that N_o is the total number of eggs spawned), and available production were, respectively: 13502-85776 ind. ha⁻¹, 178.6–221.3 kg ha⁻¹, 221.7–583.6 kg ha⁻¹ yr⁻¹, 118.1–271.9 kg ha⁻¹ yr⁻¹. Production estimates based on mortality curves were 7.9–19.5% (mean: 13.7) lower than those based on estimated from the number of eggs laid. Production per unit of area was highest at the widest and deepest site. Brown trout production contributed only 2–4% of the total production for all sites.     

Does the stock density of stillwater catch and release fisheries affect the growth performance of introduced cultured barbel?

In comparison to barbel Barbus barbus in their natural, riverine environment, the growth performance of cultured barbel, following introduction into stillwater environments, was depressed when the extant stock density was above 500 kg ha⁻¹ and common carp Cyprinus carpio were present.     

Juvenile salmonid production in a Lake Erie nursery stream

Normandale Creek (2531m²) provides spawning and nursery grounds for lake-run rainbow trout, Salmo gairdneri Richardson, brown trout, Salmo frutta L. , and coho salmon, Oncorhynchus kisutch (Walbaum). Upstream movements are significantly correlated with peak stream discharge (P < 0.05). In 1973–1974, 59 adult salmonids constructed 86 nests of which 60% were disturbed by re-use or sand deposition. From a calculated deposition of 90 400 ova, 483 juveniles, 6 cm in fork length ( f.l. ), were resident in the stream when estimates by electrofishing first became valid. Estimated within-stream (i.e. all sections combined) monthly densities of wild juveniles >6 cm f.l. ranged from six to 22 fish (100 m²)⁻¹, and biomass from 1.3 to 3.1 gm⁻². The highest within-section biomass was 8.3 gm⁻² in November. Additions of hatchery-reared rainbow trout temporarily increased monthly within-stream juvenile density up to 23 fish (100 m²)⁻¹, and biomass to 8.2 g m⁻². Density and biomass were positively correlated (P < 0.05) with both instream and bank cover, and biomass negatively correlated (P < 0.05) with gradient. The importance of substratum and flow characteristics on juvenile density and biomass was strongly indicated although not statistically significant. Annual within-section production of juveniles > 6 cm f.l. ranged from 4.79 to 5.93 g m⁻² year⁻¹ in Sections III and IV, respectively. Inclusion of calculated probable numbers of fish < 6 cm f.l. increased within-section production from 5.93 to 18.65 g m⁻² year^−l in upstream Section IV.     

Benthic macroinvertebrates of a fluctuating reservoir

SUMMARY. Benthic macroinvertebrate distribution, abundance, and composition were observed in a fluctuating (7.7 m) central Wisconsin, U.S.A., reservoir during 1973–74. Chironomidae and Oligochaeta represented 98% of the total fauna by number. The chironomid, Chironomus plumosus , and an oligochaete, Limnodrilus , each averaged 36% of the total benthic biomass. Annual mean numbers and biomass in areas exposed to air, exposed to ice cover, or remaining inundated were 3025/m² (1.8g/m²), 4311/m² (4.5g/m²), and 8558/m² (16.0 g/m²), respectively. A substantial portion of the benthic fauna was stranded and subsequently decreased rapidly in drying and frozen substrates exposed to air. Total benthic numbers and biomass were greatest immediately below the drawdown limit.
Recolonization required 3 months (mid-March to mid-June, 1974) to attain pre-drawdown values for numbers and biomass, and subsequently both were greater after reinundation than before the substrate was exposed. Recolonization of areas exposed to the air was greater in substrates containing large amounts of organic matter than in sandy areas containing little organic matter. Sorting and transportation of sediments redistributed organic materials from the regulated zone to below the drawdown limit, and macrophytes were eliminated from the regulated zone. When compared to other reservoirs and lakes, the density of benthos in the Big Eau Pleine Reservoir is neither high nor low. However, when compared with non-fluctuating reservoirs the number of Ephemeroptera, Plecoptera, Trichoptera, Amphipoda, and Gastropoda was low.     

Effect of increased flow on the behaviour of Atlantic salmon parr in winter

The effect of increased flow on movement and microhabitat use of Atlantic salmon Salmo salar parr in winter was investigated using radiotelemetry. To simulate hydropeaking operations, flow was increased four‐fold from 1·3 m³ s⁻¹ to 5·2 m³ s⁻¹ for 24 h periods. Flow did not affect fish habitat use or displacement and had little effect on fish activity within diel periods. During high flow periods in late winter, fish reduced night‐time activity. Stranding rates during flow reduction were also very low (only one fish).     

Comparative primary productivity of algal epiphytes on three species of macrophyte in the littoral zone of Lake Ohrid, Yugoslavia

Primary productivity of algal epiphytes on the surfaces of Phragmites, Potamogeton , and Nuphar was measured seasonally from June 1978, through June 1979, in the littoral zone of Lake Ohrid, using ¹⁴C methodology. Surface areas of individual macrophytes were determined throughout the study period through the use of a non-miscible surfactant and a calibration curve of surfactant weight versus known, calculated surface areas.
Mean total surface area available for epiphytic colonization during the study period was 1.032 m² macrophyte surface per m² of littoral zone for Phragmites , 0.810 m² for Potamogeton , and 0.167 m² for Nuphar . Seasonal rates of mean primary productivity of algal epiphytes on Phragmites from the surface to the light-compensation depth ranged from 84–1406 mg C m⁻² littoral zone d⁻¹; ranges for epiphytes on Potamogeton and Nuphar were 77–586 and 69–268 mg C m⁻² littoral zone d⁻¹, respectively. Maximum rates were observed typically during June; minimum rates were observed typically during August to December. Mean daily productivity rates over the 12 month period were for epiphytes on Potamogeton 167.0, on Nuphar 100.4 and on Phragmites 671.2 mg C m⁻² littoral zone d⁻¹. Calculated annual production for epiphytes on Nuphar was 36.65, on Potamogeton 60.95 and on Phragmites 245.0 g C m⁻² littoral zone yr⁻¹. Epiphytic production data were typically considerably higher than production data obtained for littoral and pelagial planktonic algae and compare favorably with published data for epiphytic and periphytic production in Lawrence Lake, Marion Lake, and Borax Lake.     

Territorial defence by the Brazilian damsel Stegastes fuscus (Teleostei: Pomacentridae)

Territorial defence by Brazilian damselfish Stegastes fuscus was studied in north-east Brazil through underwater observations. The fish mostly fed on Gellidium sp. and strongly defended a territory with a mean size of 2 m² (range 1·27–3·07 m²); its mean ± s.d. feeding rate was 8·73 ± 2·44 bites min⁻¹. Stegastes fuscus responded similarly to all intruding fish species, with aggressive behaviour becoming more pronounced only with an increase in the number of fishes in the sampled area. Analysis of attacks elicited by different fish species placed within S. fuscus ' territory, however, showed that it launched more attacks on conspecifics than on other fishes.     

Spatial organization and population density of the fish community of the litter banks within a central Amazonian blackwater stream

Results of a study of the fish community of the leaf litter banks in the lower reaches of the Taruma-Mirim, a small central Amazonian stream is presented. The Taruma-Mirim is an acidic, blackwater, forest stream which flows through igapo forest and enters the Rio Negro close to Manaus. The commonly held view that these blackwaters hold an impoverished ichthyofauna is challenged. The studied litter banks hold about 20 species of fish, all of which were found to live within distinct subregions of the habitat. Average fish density was about 100 individuals m⁻². Absolute population sizes were found to be remarkably small; within a 200 m² area the most abundant species had a population size of about 10⁴ and the least abundant <10² individuals. It is argued that high species richness linked to specialized habitat requirements and small population size indicates considerable population stability. The factors leading to the evolution of such species richness are discussed.     

Biological Control of Anopheles sinensis with Native Fish Predators (Aplocheilus and Aphyocypris) and Herbivorous Fish, Tilapia in Natural Rice Fields in Korea

ABSTRACT A confined field experiment was conducted to investigate biological control of malaria and inland filariasis vector, Anopheles sinensis Wied. by combined use of larvivorous fishes, Aplocheilus latipes or Aphyocypris chinensis and herbivorous, Tilapia mossambicus niloticus in natural rice fields at Banwol near Suwon, Gyeonggi province from June through October, 1989. In the presence of naturally breeding Aplocheilus at the density of 0.8 fish/m² water surface, the natural control of Anopheles larvae ranged 34.4% to 51.6% from June through August; later supplemental introduction of herbivore (Tilapia) at the release rate of 1-pair per 10 m² resulted in 67.8% increased to 80.0% control of Anopheles sinensis in 3rd and 5th week respectively. In a combined fish release at the rate of 1.0 fish/m² of Aphyocypris and 1-pair/10 m² of Tilapia produced 67.3% and 82.1% mosquito larval reduction in 3rd and 5th week periods, respectively. The similar pattern of gradual but significant suppression of mosquitoes was also evident in separate rice paddy in 4-5 week period, maintaining ca. 75'82% for the subsequent mosquito breeding season in comparison with control plot.     

The populations of fish in the River Tees system on the Moor House National Nature Reserve, Westmorland

The age, growth, population densities and annual production of an isolated population of brown trout ( Salmo trutta L.) and bullhead ( Coitus gobio L.) were investigated over a 5 year period in Trout Beck in the northern Pennines. Additional data were obtained from two other sites; Great Dodgen Pot Sike and the River Tees.
Trout growth rates were low, particularly in Dodgen Pot Sike, but ages up to VIII were recorded. Bullhead growth rates were similar to those in the Tees at Cow Green (Crisp et al. , 1974), though the Moor House bullheads had a higher survival rate. Population densities of trout ranged from 0.10–0.22/m², with a fry contribution of 0.80%. The bullhead population in Trout Beck was sparse, generally 0.1/m², though an 0 group value of 0.46/m^a was estimated in 1967. At Tees Bridge values ranged from 2.5–7/8/m². Most trout matured by age III, though in Great Dodgen Pot Sike only half of the females were mature at age IV.
Annual production was estimated from Allen graphs. Trout production ranged from 1.02–3.50 g/m²/year, the fry contributing up to 51.5% of the total. A value of 0.48 g/m²/year was obtained for bullheads in the Trout Beck system in a year of good recruitment, whilst bullhead production at Tees Bridge was 7.43 g/m²/year, with fry and I group contributing 48.7 and 37.5% respectively. The high survival rate, irregular recruitment, and poor growth of these high altitude populations is discussed. Growth and reproductive peculiarities of the Great Dodgen Pot Sike trout are also discussed.     

Toxicity of six commercially formulated insecticides and biopesticides to third instar larvae of mushroom sciarid, Lycoriella ingenua Dufour (Diptera: Sciaridae), in New South Wales, Australia

Abstract  Lycoriella ingenua is one of the major pests of cultivated mushrooms, Agaricus bisporus (Lange) Imbach . Insecticide resistance among mushroom sciarid populations has been reported from other countries, and there is a need to determine the toxicity of currently approved and potential pesticides to sustain control of mushroom sciarid populations in Australia. The present study investigated the toxicity of six commercial formulations of insecticides or biopesticides against third instar larvae of L .  ingenua using laboratory bioassays. Insecticide treatments were incorporated into the growing medium for sciarid larvae and the concentration of the pesticide, which killed 90% of the test population (LD₉₀) determined the efficacy of selected insecticides. Triflumuron was the most effective insecticide against L. ingenua with an LD₉₀ of 53.12 mg active ingredient (a.i.)/m² followed by cyromazine (LD₉₀, 179.68 mg a.i./m²) and diazinon (LD₉₀, 261.72 mg a.i./m²). Abamectin and Bacillus thuringiensis ssp. israelensis were ineffective against L. ingenua . Steinernema feltiae , an entomopathogenic nematode, reduced the number of third instar larvae of L. ingenua only when applied at a higher rate (LD₉₀, 732 422 nematodes/m²) than was recommended on the label.     

Spatial patterns of the biological traits of freshwater fish communities in south‐west France

Spatial patterns in the combinations of biological traits of fish communities were studied in the Garonne River system (57 000 km², south‐west France). Fish species assemblages were recorded at 554 sampling sites, and the biological traits of species were described using a fuzzy‐coding method. A co‐inertia analysis of species distributions and biological traits identified some spatial patterns of species trait combinations. Fish species richness progressively increased from up‐ to downstream sections, and the longitudinal patterns of fish assemblages partitioned the river into clear biogeographic areas, such as the brown trout Salmo trutta (headwater streams), the grayling Thymallus thymallus , the barbel Barbus barbus and the bream Abramis brama zones (most downstream sections), which fitted with Huet's well‐known zonation for western European rivers. Only a few biological traits, chiefly related to life‐history attributes, significantly influenced the observed fish distributions. Fecundity, potential size, maximum age and reproductive factor increased from headwater to plain reaches. As a theoretical framework for assessing and predicting the functional organization of stream fish communities, spatial variations in species traits can be related to habitat conditions, thus providing explicit spatial schemes that may be useful to the design of both scientific studies and river management.     

The Contribution of Ciliated Protozoa to Plankton and Benthos Biomass in a European Ricefield

The densities and biomass of ciliates inhabiting the water-sediment interface and the water column of an experimental ricefield were investigated throughout four annual cycles. Ciliate abundance and biomass were higher at the water-sediment interface than in the water column. In both sites, large ciliates (> 10⁵μm³) contributed the higher biomass values, but the highest densities were found in the intermediate size class (10⁴-10⁵μm³). The prorodontid Coleps hirtus dominated the ciliate assemblage and usually comprised > 50% of total ciliate density. Blooms of C. hirtus , occurred in June in the water column and in July at the sediment surface. During the four cycles of rice cultivation, the average daily values for production of the entire ciliate community was 69.6 mgC/m²/d, and the net production efficiency (K₂) was 72.0%. The estimated production values in the present study are high if compared to production measured for ciliates in other freshwater ecosystems.     

Relationship between seed and clonal growth in the reproduction of Carex rugulosa Kük. in riverside meadows

Carex rugulosa Kük. develops riverside vegetation in brackish marshes along the lower parts of rivers. Because the rhizomatous ramets grow densely (590–950/m²) in its developed population, it is expected that seedlings cannot get enough light to grow if seeds germinate in crowded ramets. We studied the reproductive contribution of seed in a marshy meadow of the Ohashi River, Japan. The number of seeds produced was 6900–14 200/m² in 2002. The number of buried seeds in the following germination season differed among sites from 1190 to 2690/m². No seedlings were observed at plots where the ramets from rhizomes grew densely. In contrast, seedlings appeared in plots where all rhizomatous ramets were artificially cut. The number of seedlings corresponded to 17.5–39.5% of that of buried seeds. All these seedlings were submerged and died when it rained heavily. In the genotype analysis using allozyme detection, one of the phosphoglucoisomerase loci ( Pgi-2 ) indicated a pair of alleles. Among eight plots (each plot was 50 or 60-cm square), four showed an excess of heterozygotes and two showed homozygote domination in the Pgi-2 genotype. These results suggest that: (i) seed germination is suppressed in crowded ramets; (ii) seedling survival is severely reduced by inundation; and (iii) the population is usually maintained by clonal growth. As germination is induced in open areas, it is hypothesized that the main role of seed is recovery after vegetation decline caused by environmental stresses or colonization to other areas without dense vegetation.     

River flow and fish abundance in a South African estuary

The ichthyofauna of the Thukela Estuary, a small (55 ha), shallow (<1·5 m) system on the KwaZulu-Natal coast (mean annual river runoff of 3865 × 10⁶ m³, from a large catchment of 29 000 km², is seasonal: peak inputs occurring between November and March), was dominated by the juveniles of marine taxa that used the estuary as a nursery area. A striking feature of the above community was the decline in fish abundance with increasing river input, with flow values >100 m³ s⁻¹ leading to increased loss of species from the system. This decline was linked to the lack of saline intrusion into the estuary and increased freshwater flooding through the system.