The influence of drought on the fish and invertebrate populations of an upland stream in Wales

SUMMARY. 1. The exceptionally dry summer of 1976 presented an opportunity to assess the impact of drought on the fauna of an unregulated stream in Wales.
2. Total number of macroinvertebrates varied from 1808 m⁻² in September 1976 to 7412m⁻² in August 1977. Two main effects of drought were observed: an initial reduction in abundance during the drought and a change in community structure in the following year, probably through impaired reproduction.
3. Trout density ranged from 0.075±0.028 to 0.402±0.093 m⁻² and salmon parr density varied between 0.014±0.004 and 0.414±0.119 m⁻². The only detrimental effect of the drought on the fish fauna was the elimination of the 1976 year class of young salmon. probably due to prolonged high water temperature.     

The appropriation of an Aboriginal landscape in northern New South Wales

The attachment of Australian Aboriginal people to land has not only been amply documented by anthropologists since the late 19^th century, it is also one of their own enduring tropes of differentiation from non‐Aboriginal and “official” Australian state society. In the face of widespread and concerted alteration of the pre‐settlement landscape engendered by industrial and commercial development, Aboriginal people seek to reclaim or reappropriate remnants of a pristine environment untransformed by modern development. Alteration of the landscape, as far as Aboriginal people are concerned, also goes hand in hand with the progressive decimation of Aboriginal populations in the 19^th and early 20^th centuries through violence and disease. Contemporary Aboriginal communities seek to protect the sites of violent death, believed heavily populated with the frustrated spirits of the deceased, from disturbance, particularly by non‐Aboriginal people. In this chapter I discuss some of the anthropological implications of seeing landscape as a terrain of intercultural conjunction in such a bifold society in northern New South Wales, and what levels of transformation are and are not acknowledged by a marginal, minority indigenous population seeking to insulate their historical landscape from development.     

The movement of hatchery-reared rainbow and brown trout in a polluted river in the South Wales coalfield

Hatchery reared rainbow and brown trout (length 20 cm) were released in March 1974 and April 1975 respectively into the Taff Bargoed, a small river in South Wales, polluted by coal wastes and containing a low resident population of brown trout. From subsequent electro-fishing surveys and catch returns from anglers, extensive downstream movements occurred in both species. About 50% had either been caught or had moved out of the river, a distance of about 5 km, after two weeks and after two months only some 10 % remained. Within the fishing season it was estimated that 3 and 22% of brown and rainbow trout respectively were caught.     

Reproduction of river and lake populations of Hyridella depressa (Unionacea: Hyriidae) in New South Wales: implications for their conservation

The freshwater mussel Hyridella depressa is an important component of the macrobiota of freshwater systems of south-eastern Australia. This species has declined in river habitats but is abundant in impounded water storages. Reproduction of river and lake populations of H. depressa was investigated to document details of their gametogenic cycle and to determine when the females incubate embryos in their gill marsupia. Four populations in Lake Burragorang and two populations in the Hawkesbury-Nepean River were studied over two breeding seasons. Reproduction was documented by anatomical and histological examination of the gonads. The study sites differed in anthropogenic influence and trophic status and the influence of these factors on reproduction in H. depressa was assessed. A skewed sex ratio in favour of females was common in the populations and histology revealed that some of these females were microhermaphrodites. It appears that sexuality in H. depressa is labile with the potential for self-fertilisation by individuals that largely function as females. H. depressa is a long-term brooder with progeny present in the marsupia for up to eight months of the year from mid-winter to late summer. Across all sites brooding started in July or August and finished in January or February of the following year. In parallel with the prolonged spawning pattern, gametogenesis in H. depressa was continuous. At the eutrophic sites the gonads contained advanced gametes throughout the year. H. depressa at these sites had a high annual reproductive output with the females producing several clutches each year. In contrast, gametogenesis in mussels at the oligotrophic sites was more seasonal. At one of the oligotrophic sites reproductive failure was common and in 1996 most females failed to brood a single clutch. Implications of this research for conservation of H. depressa are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

The fish populations of some streams in Wales and northern England in relation to acidity and associated factors

Electrofishing and water quality surveys were carried out on 60 upland moorland streams in central and north Wales and the Peak District of England (south Pennines). A number of biological characteristics of the fish populations were recorded, including species representation, population density and biomass and, for brown trout, Salmo trutta L., only, growth, condition factor and diet. The stream waters were also analysed over a 2-year period for pH, calcium, aluminium and the heavy metals copper, zinc and lead.
Mean pH levels in the streams ranged from 5.0 to 7.6, with calcium concentrations in the range 0.80–27 mg 1⁻¹. Trace metal concentrations (Al, Cu, Zn, Pb) tended to be elevated in the more acid streams. The latter had fewer fish species, and a higher proportion was fishless, 73% at pH < 5.5 compared with 6% at pH >6.5. Trout and eels, Anguilla anguilla L., predominated at lower pH values, but at reduced population levels.
Dietary composition and stomach fullness of trout were similar throughout the stream pH range. More than 40% of the diet was derived from surface and terrestrial sources, supplementing autochthonous items. Growth (as back-calculated length to end of first year of life) and condition factor did not vary significantly with respect to stream acidity. It is thus concluded that the impoverishment of trout populations in the more acid streams was not a second-order effect acting through the lower trophic levels.
Water quality acting directly on fish would appear to account for the poor status of salmonid fisheries in acid streams. Absence or paucity of salmonids was related to high levels of labile monomeric aluminium (>40 μgl⁻¹) or Cu-Zn-Pb toxicity (>0.4 t-LC50 to rainbow trout, Salmo gairdneri Richardson). Limiting values in this study correspond well with published laboratory and field data.     

Adaptive phenotypic plasticity contributes to divergence between lake and river populations of an East African cichlid fish

Adaptive phenotypic plasticity and fixed genotypic differences have long been considered opposing strategies in adaptation. More recently, these mechanisms have been proposed to act complementarily and under certain conditions jointly facilitate evolution, speciation, and even adaptive radiations. Here, we investigate the relative contributions of adaptive phenotypic plasticity vs. local adaptation to fitness, using an emerging model system to study early phases of adaptive divergence, the generalist cichlid fish species Astatotilapia burtoni. We tested direct fitness consequences of morphological divergence between lake and river populations in nature by performing two transplant experiments in Lake Tanganyika. In the first experiment, we used wild‐caught juvenile lake and river individuals, while in the second experiment, we used F1 crosses between lake and river fish bred in a common garden setup. By tracking the survival and growth of translocated individuals in enclosures in the lake over several weeks, we revealed local adaptation evidenced by faster growth of the wild‐caught resident population in the first experiment. On the other hand, we did not find difference in growth between different types of F1 crosses in the second experiment, suggesting a substantial contribution of adaptive phenotypic plasticity to increased immigrant fitness. Our findings highlight the value of formally comparing fitness of wild‐caught and common garden‐reared individuals and emphasize the necessity of considering adaptive phenotypic plasticity in the study of adaptive divergence.     

Distribution of bacterial plasmids in clean and polluted sites in a South Wales river.

We isolated 400 aerobic heterotrophic bacteria from the sediment of unpolluted and polluted sites in a fast-flowing south Wales river. Isolates were subjected to taxonomic tests and screened for the presence of plasmid DNA by alkaline lysis and agarose gel techniques. There were no significant differences between sites in either the total percentage of isolates containing plasmids (unpolluted site, 9.4%; polluted site, 15%) or in the percentage of non-Pseudomonas-like isolates containing plasmids (unpolluted site, 15%; polluted site, 10%). There were significantly more Pseudomonas-like isolates with plasmids at the polluted site than at the unpolluted site (unpolluted site, 7%; polluted site, 18%). This presumably reflected a response of the nutritionally versatile Pseudomonas-like isolates to conditions at that site. The majority (86%) of the plasmids detected had molecular masses between 35 and 312 megadaltons. These plasmids were large enough to carry genes for conjugal transfer, suggesting the possibility of such transfer in this environment.     

The effects of coal industry pollutants on the macroinvertebrate fauna of a small river in the South Wales coalfield

SUMMARY. The effects of pollutants from the coal industry on the macroinvertebrate fauna of a small river in the South Wales coalfield were investigated during 1972 and 1973.
Three major types of pollution, each spatially separate, affected the river and its tributaries. The upper reaches received acidic drainage from coal stockpiles. The lower reaches received a discharge from a drift mine, bearing high loads of suspended coal particles which caused siltation of the river bed downstream to its confluence with the R. Taff (3.5 km). The largest tributary was subjected, under neutral pH, to siltation by ferric hydroxide, derived from seepage from an abandoned mine.
In the upper reaches, a few acid-tolerant invertebrate species survived in low numbers. Downstream recovery was not complete before the discharge of coal particles. In the reaches silted by ferric hydroxide or coal there was a pronounced reduction (80–90%) in faunal abundance. Clear differences in sensitivity of invertebrate groups to these types of siltation were apparent.
The data are used to assess the various methods of biological surveillance involving invertebrates.     

The Oriental Goby, Acanthogobius flavimanus (Temminck and Schlegel), an introduced fish in the coastal waters of New South Wales, Australia

Since 1971 over 100 specimens of the oriental goby, Acanthogobius flavimanus , have been collected from New South Wales' waters. When this species, a native of Japan, was introduced to San Francisco Bay (U.S.A.) it underwent a population explosion, becoming a common member of estuarine fish communities in that area.
The occurrence of both reproductively maturing females and juveniles in the harbours of the Sydney region (central New South Wales coast) suggests that the species may have bred successfully here. However, the relatively low numbers of A. flavimanus collected during the study indicate that as yet there has been no population explosion in New South Wales waters. A number of aspects of the biology and ecology of the species was examined in an attempt to identify features which may limit its distribution and abundance in the Sydney region.
The inhibition of successful reproduction by the relatively warm-water temperatures in this area and the potential for competition with native fishes are proposed as possible explanations.     

Temporal and geographical distributions of epilithic sodium dodecyl sulfate-degrading bacteria in a polluted South Wales river

Epilithic bacteria were isolated nonselectively from riverbed stones and examined by gel zymography for their ability to produce alkylsulfatase (AS) enzymes and thus to metabolize alkyl sulfate surfactants such as sodium dodecyl sulfate. The percentages of AS+ isolates from stone epilithon at five sites from the source to the river mouth were measured on five sampling days spread over 1 year. The results showed that (i) the prevalence of epilithic AS+ strains (as a percentage of all isolates) was much higher at polluted sites than at the source; (ii) when averaged over the whole river, percentages of AS+ strains were significantly higher at the end of summer compared with either the preceding or the following winter; (iii) analysis of site-sampling time interactions indicated that water quality factors (e.g., biochemical oxygen demand and dissolved oxygen concentration) rather than climatic factors determined the distributions of epilithic AS+ isolates; (iv) constitutive strains were the most prevalent (7.2% of all isolates), with smaller numbers of isolates with inducible (4.5%) and repressible (1.7%) enzymes.     

A field investigation of water quality, fish and invertebrates in the Mawddach river system, Wales

A 3-year study was made of the soft, acid waters of the Rivers Mawddach, Wen and Gain, which contained copper, zinc and iron from natural outcrops and abandoned mines. Invertebrates, typical of acid to neutral streams, were present but there was no pattern in overall numbers or in biomass between stations. However, the abundance and distribution of Ephemeroptera were related to pH and water hardness although not to copper and zinc. Brown trout, Salmo trutta , were present and there was little difference in rate of growth between stations, whereas biomass and population density varied considerably between stations, being related to water quality such that, where annual median and 95-percentile of the summed proportions ( p ) of the threshold LC50 concentrations of copper and zinc to rainbow trout, S. gairdneri were 0·3 and 0·7 respectively, biomass was half that in the absence of the metals and, where they were 0·6 and 1·3 respectively, no fish would be expected to occur. Low pH was an additional adverse factor at some locations. Salmon, S. salar , failed to populate a tributary where the sum of the p t LC50 values of copper and zinc was 0·45. High aqueous concentrations of copper resulted in elevated concentrations of copper in the liver of trout, especially in older fish, but not in the muscle. Concentrations of zinc in fish liver and muscle were low despite high ambient concentrations.     

Abundance and diversity of macroinvertebrates and fish in the Tamiraparani river, South India

Occurrence of macroinvertebrates and fish was studied at 11 stations along the course of a tropical river, Tamiraparani, South India. Monthly variations in macroinvertebrate density were studied during 1991. Among macroinvertebrates, hemipterans were the dominant group at all sites, except site 2. Using an ordination technique, density and occurrence of macroinvertebrates were correlated with dissolved oxygen, biological oxygen demand and chemical oxygen demand. A total of 36 species of fish was recorded and their diversity in undisturbed and disturbed regions of the river was compared on a spatial scale. Different diversity indices were calculated to assess fish response to pollution and to determine species richness and composition.     

The dynamics of fish populations in the Palancar stream,a small tributary of the river Guadalquivir,Spain

The relationship between flooding and changes in the size distribution of fish populations in the Palancar stream confirms observations in other rivers. On average, density decreased by 36.2 % and biomass increased by 14.5 %, passing from a period of severe drought to one of heavier than normal rains. Precipitation is the most important of the many factors affecting the populations of the Palancar stream; the most evident changes all occurred after the drought. During the drought period, the marked seasonal fluctuation in flow was the most important factor regulating the population dynamics. Fish density and biomass varied in proportion to the water volume. During the rainy period, the studied section of the river was found to be an important reproduction and nursery area, with juveniles and individuals of reproduction age dominating. The presence of Micropterus salmoides, an introduced piscivorous species, is another factor affecting the population dynamics in the Palancar stream. The observed absence of age 0+ individuals of the dominant populations is considered a direct effect of predation.