Lakes and rivers as islands: species-area relationships in the fish faunas of Ontario

Synopsis Fish species richness in 82 lakes in Ontario, Canada was significantly correlated with surface area. In this region, latitude explained only a small amount of the variation in fish species richness. Thus, our study provides a clear demonstration of the relation between fish species richness and lake area without the confounding effects of latitude and physiography inherent in analyses from broader geographic regions. By comparison with the species-area relationship obtained, we show that acidification clearly depressed the number of fish species in 66 acid-stressed lakes in Ontario. Fish species richness was also significantly correlated with both drainage and surface areas of 21 Ontario rivers. Slopes of species-area regressions of lakes and rivers did not differ significantly, suggesting that species are added to these habitats at similar rates. However, our regression analyses show that rivers support more species of fish per unit surface area of water. Although these results are consistent with some predictions of island biogeography theory, we suggest that fish species richness is more likely to be a simple function of habitat diversity, rather than an equilibrial balance between immigration and extinction.     

Movements of diadromous fish in large unregulated tropical rivers inferred from geochemical tracers

Patterns of migration and habitat use in diadromous fishes can be highly variable among individuals. Most investigations into diadromous movement patterns have been restricted to populations in regulated rivers, and little information exists for those in unregulated catchments. We quantified movements of migratory barramundi Lates calcarifer (Bloch) in two large unregulated rivers in northern Australia using both elemental (Sr/Ba) and isotope ((87)Sr/(86)Sr) ratios in aragonitic ear stones, or otoliths. Chemical life history profiles indicated significant individual variation in habitat use, particularly among chemically distinct freshwater habitats within a catchment. A global zoning algorithm was used to quantify distinct changes in chemical signatures across profiles. This algorithm identified between 2 and 6 distinct chemical habitats in individual profiles, indicating variable movement among habitats. Profiles of (87)Sr/(86)Sr ratios were notably distinct among individuals, with highly radiogenic values recorded in some otoliths. This variation suggested that fish made full use of habitats across the entire catchment basin. Our results show that unrestricted movement among freshwater habitats is an important component of diadromous life histories for populations in unregulated systems.     

The disregarded West: diet and behavioural ecology of olive baboons in the Ivory Coast

Despite living under environmental conditions considerably distinct from those of savannah baboons (Papio spp.) in East and southern Africa, very little is known about western Papio populations. We monitored the abundance and group sizes of olive baboons (P. anubis) in the savannah-forest mosaic of the Comoé National Park, northern Ivory Coast, and observed 2 habituated groups of different sizes. Against expectations for the kind of habitat, the individual density was low, yielding only 1.2 baboons/km(2). The groups were small, comprising on average 15 individuals, and the proportion of 1-male groups (50-63%) was remarkably high. One-male groups were more female biased than multi-male groups. The baboons were highly frugivorous, spending about 50% of their feeding time on fruits and seeds of at least 79 woody plant species. The 2 habituated groups had comparatively large home ranges and used forests more often than expected by random. We argue that regular subgrouping of the larger focal group and different habitat quality countervailed inter-group variations. Differences from other study sites, however, are not completely explained by current models of baboon (socio)ecology. It appears that the social organization of olive baboons is more flexible than assumed from data on East African populations.     

The stable carbon isotope ratios of fish and their invertebrate prey in four New Zealand rivers

SUMMARY.

• 1 Sources of carbon utilized by invertebrates and fish in four New Zealand streams were investigated using stable carbon isotope analysis. Complementary analyses were made to determine σ¹³C alteration (fractionation) by fish reared on a known food and to examine the distribution of ¹³C/¹²C ratios in different tissues.
• 2 σ¹³C values of hatchery-reared rainbow trout (white muscle tissue) were ¹³C-enriched compared with their food (trout pellets) by an average of 1.7%₀. σ¹³C values of different organs and tissues never differed by more than 1.8%_o in any fish species; white muscle always had an intermediate value.
• 3 σ¹³C values of invertebrates ranged from-28.4 to –20.4%_o– At the more open sites invertebrates were ¹³C-depleted, reflecting some use of algal carbon. However, invertebrates from the most heavily shaded stream site were unusually enriched in ¹³C. An undetected carbon source of terrestrial origin, perhaps ¹³C-enriched dissolved organic carbon in groundwater, may have been contributing indirectly to invertebrate biomass carbon.
• 4 σ¹³C values for fish were not closely linked to aquatic invertebrate ratios; instead, at all sites their carbon was isotopically similar to terrestrial organic carbon. The reasons for this apparent anomaly are unclear.

     

West African rivers as biogeographic islands: species richness of fish communities

Summary Some factors influencing the species richness of West African fish communities were studied in a sample of 26 rivers using four habitat and hydrologic variables. Analysis of a larger sample of 39 rivers showed that species richness was positively related to area. A power function with an exponent of 0.32 gave the best fit. As the surface area used was that of the catchment area and not that (unknown) of the river, the biological significance of this relationship and the possibilities of comparison were limited. Ridge regression analysis and forward stepwise selection indicated that a model that explained ln(species richness) as a function of ln(mean annual discharge) and ln-(catchment surface area) was best, accounting for 90% of the variance of the dependent variable. The combination of surface area and discharge was presumed to act through the volume of water available for the fishes and habitat productivity. Habitat diversity, measured by the diversity of the terrestrial vegetation covering the catchment area, had no significant positive effect when surface area was used in the regression. Rivers (islands) should have fewer species than tributaries of similar size since, for fishes within a river system (continent), there is free circulation between all its branches. The model derived from the river data underestimated the species richness of a sample of 11 tributaries. This was compatible with the hypothesis of higher population extinction rates in insular biotopes. The residuals of the linear model did not show random geographical distribution; the rivers in some areas had more species than expected. The possibility that historical factors, especially Quaternary climatic variations, might cause this distribution is discussed.     

Relationship between flow regime and fish abundances in a gravel‐bed river, New Zealand

The key elements of the flow regime of the Waipara River on the east coast of New Zealand, that affected fish abundances were the timing of floods and the magnitude and duration of low flows. Generally, fish abundances were highest in early summer, and lowest at the beginning of winter. Spring floods opened the river mouth, allowing recruitment of diadromous fish species, and non‐diadromous fish species spawned after the floods in spring or early summer. Reductions in fish abundances over summer and autumn were consistent with the magnitude and duration of low flows, with significant reductions in the year of lowest flow and little change in abundance in the year when low flows were highest. Variations in fish abundances during periods of low flow were consistent with the amount of instream habitat available, such that abundances of species with high velocity preferences decreased during periods of low flow, whereas abundances of species with low velocity preferences increased.     

Seasonal variability of methane in the rivers and lagoons of Ivory Coast (West Africa)

We report a data-set of dissolved methane (CH₄) in three rivers (Comoé, Bia and Tanoé) and five lagoons (Grand-Lahou, Ebrié, Potou, Aby and Tendo) of Ivory Coast (West Africa), during the four main climatic seasons (high dry season, high rainy season, low dry season and low rainy season). The surface waters of the three rivers were over-saturated in CH₄ with respect to atmospheric equilibrium (2221–38719%), and the seasonal variability of CH₄ seemed to be largely controlled by dilution during the flooding period. The strong correlation of CH₄ concentrations with the partial pressure of CO₂ (pCO₂) and dissolved silicate (DSi) confirm the dominance of a continental sources (from soils) for both CO₂ and CH₄ in these rivers. Diffusive air–water CH₄ fluxes ranged between 25 and 1187 μmol m^?2 day^?1, and annual integrated values were 288 ± 107, 155 ± 38, and 241 ± 91 μmol m^?2 day^?1 in the Comoé, Bia and Tanoé rivers, respectively. In the five lagoons, surface waters were also over-saturated in CH₄ (ranging from 1496 to 51843%). Diffusive air–water CH₄ fluxes ranged between 20 and 2403 μmol m^?2 day^?1, and annual integrated values were 78 ± 34, 338 ± 217, 227 ± 79, 330 ± 153 and 326 ± 181 μmol m^?2 day^?1 in the Grand-Lahou, Ebrié, Potou, Aby and Tendo lagoons, respectively. The largest CH₄ over-saturations were observed in the Tendo and Aby lagoons that are permanently stratified systems (unlike the other three lagoons), leading to anoxic bottom waters favorable for a large CH₄ production. In addition, these two stratified lagoons showed low pCO₂ values due to high primary production, which suggests an efficient transfer of organic matter across the pycnocline. As a result, the stratified Tendo and Aby lagoons were respectively, a low source of CO₂ to the atmosphere and a sink of atmospheric CO₂ while the other three well-mixed lagoons were strong sources of CO₂ to the atmosphere but less over-saturated in CH₄.     

Using multivariate adaptive regression splines to predict the distributions of New Zealand's freshwater diadromous fish

1. Relationships between probabilities of occurrence for fifteen diadromous fish species and environmental variables characterising their habitat in fluvial waters were explored using an extensive collection of distributional data from New Zealand rivers and streams. Environmental predictors were chosen for their likely functional relevance, and included variables describing conditions in the stream segment where sampling occurred, downstream factors affecting the ability of fish to move upriver from the sea, and upstream, catchment‐scale factors mostly affecting variation in river flows. 2. Analyses were performed using multivariate adaptive regression splines (MARS), a technique that uses piece‐wise linear segments to describe non‐linear relationships between species and environmental variables. All species were analysed using an option that allows simultaneous analysis of community data to identify the combination of environmental variables best able to predict the occurrence of the component species. Model discrimination was assessed for each species using the area under the receiver operating characteristic curve (ROC) statistic, calculated using a bootstrap procedure that estimates performance when predictions are made to independent data. 3. Environmental predictors having the strongest overall relationships with probabilities of occurrence included distance from the sea, stream size, summer temperature, and catchment‐scale drivers of variation in stream flow. Many species were also sensitive to variation in either the average and/or maximum downstream slope, and riparian shade was an important predictor for some species. 4. Analysis results were imported into a Geographic Information System where they were combined with extensive environmental data, allowing spatially explicit predictions of probabilities of occurrence by species to be made for New Zealand's entire river network. This information will provide a valuable context for future conservation management in New Zealand's rivers and streams.     

Dispersal, disturbance and the contrasting biogeographies of New Zealand's diadromous and non-diadromous fish species

Aim To examine the relationship between diadromy and dispersal ability in New Zealand’s freshwater fish fauna, and how this affects the current environmental and geographic distributions of both diadromous and non‐diadromous species. Location New Zealand. Methods Capture data for 15 diadromous and 15 non‐diadromous fish species from 13,369 sites throughout New Zealand were analysed to establish features of their geographic ranges. Statistical models were used to determine the main environmental correlates of species’ distributions, and to establish the environmental conditions preferred by each species. Environmental predictors, chosen for their functional relevance, were derived from an extensive GIS database describing New Zealand’s river and stream network. Results In terms of geography, most diadromous species occur in a scattered fashion throughout extensive geographic ranges, and occupy large numbers of catchments of widely varying size. By contrast, most non‐diadromous species show relatively high levels of occupancy of smaller geographic ranges, and most are restricted to a few large catchments, particularly in the eastern South Island. In terms of environment, there is marked separation of diadromous from non‐diadromous species, with diadromous species generally caught most frequently in low‐gradient coastal rivers and streams with warm, maritime climates. With a few notable exceptions, most diadromous species have lower occurrence in river segments that are located above obstacles to upstream migration. Non‐diadromous species are usually caught in inland rivers and streams with cool, strongly seasonal climates, typified by a low frequency of high‐intensity rainfall events. Main conclusions We interpret the contrasting biogeographies of New Zealand’s diadromous and non‐diadromous species as reflecting interaction between their marked differences in dispersal ability and a landscape that is subject to recurrent, often large‐scale, natural disturbance. While both groups are likely to be equally susceptible to local, disturbance‐driven extinction, the much greater dispersal ability of diadromous species has allowed them to persist over wide geographic ranges. By contrast, the distributions of most non‐diadromous species are concentrated in a few large catchments, mostly in regions where less intense natural disturbance regimes are likely to have favoured their survival.     

Longitudinal distribution of macroinvertebrates in two glacier-fed New Zealand rivers

1. Environmental variables, benthic algal biomass and macroinvertebrate fauna were examined from September 1999 to January 2000 (austral summer) along two glacier-fed rivers in South Island, New Zealand.
2. The rivers were characterized by high flow variability, high turbidity and physically disturbed beds. Water temperature ranged from <1 °C near the glacier margin to 10 °C further downstream.
3. Epilithic algal biomass was very low (<0.1 mg m^–2) in months characterized by heavy rainfall, but ranged from 1.1 to 14.4 mg m^–2 following an extended period with negligible precipitation.
4. Abundance and diversity of invertebrates in both rivers was low. Dominant taxa were Chironomidae (Orthocladiinae, Podonominae, Diamesinae), although mayfly species ( Deleatidium : Leptophlebiidae) also occurred at most sites. A species of Eukiefferiella (Orthocladiinae) was collected at all sites and was the most abundant invertebrate close to the glacier margins. No meiofauna were found in either river.
5. Faunal diversity increased at the lowermost stations where species of Plecoptera, Trichoptera, Coleoptera and non-chironomid Diptera also occurred.
6. The faunas of the two New Zealand rivers conformed to the conceptual model of Milner & Petts (1994) in that taxon richness increased downstream with water temperature. However, invertebrate abundance increased downstream in only one of the two rivers. Also in contrast to the model predictions, Leptophlebiidae and Orthocladiinae, rather than Diamesinae, dominated the fauna at the coldest sites.     

Bryophyte ecology of a dune area in New Zealand

Summary and conclusions Bryophyte ecology has been little investigated in New Zealand. In the present study a northern dune area (under a dune reclamation and afforestation scheme) on the west coast, is divided into five community zones. Two of these are phases in the artificial sere leading from bare sand to exotic pine plantations. The others are seral stages in the development of the coastal forest climax.The bryophyte flora is investigated both quantitatively and qualitatively for the terrestrial, epixylic and corticolous habitat in each of these communities.It was found that mosses are not pioneers in the psammosere as is frequently the case in the northern hemisphere. They were secondary invaders at a late stage in the Lupinus-Psamma phase when the lupin bushes play an important part. The first bryophytes occupied epixylic stations (on logs and fallen branches). The bryophytic flora showed developmental changes in relation to the nature of the cover communities. Life form and drought tolerance of the bryophyte species are important factors. Long distance migration is by spores, but local dispersal by vegetative growth and the transportation of detached tufts is of great importance.The size and shape of quadrat for terrestrial communities is fully investigated. It was found that shape was of no essential importance in bryocoenological methods The heavy needle litter of the pine plantations had no retarding effect on the moss carpet. Succession within the bryophyte community is from hepatics to acrocarpic and then to pleurocarpic mosses.Corticolous mosses form a group apart and are affected by such factors as drainage patterns, nature of bark and exposure.The bryophyte union is worked out for each cover community and three terrestrial unions and one corticolous union are recognised. It is suggested that one of the terrestrial unions is dynamic and that basically there are two distinct terrestrial unions as a climax to the bryophyte microsere; one for the Leptospermum scrub and the other for coastal forest.My thanks are due to Prof. V. J. Chapman (Auckland University College N.Z.) for his advice and encouragement during the course of this investigation.

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Résumé Les dunes de sable très élevées sur la côte occidentale de la Nouvelle Zelande ont été fixées avec Psamma arenaria et Lupinus et plantées de Pins exotiques (Pinus radiata).Le versant Nord d'une dune a été étudié au point de vue du développement de la végétation. Ce versant comprend une partie plantée de Pinus et une autre abandonnée à l'évolution naturelle de la végétation.La flore bryophytique est divisée en trois catégories selon la station: Mousses vivant sur la terre nue, sur les arbres (Mousses corticoles) et sur le bois mort. Sur cette dune les Mousses n'apparaissent pas comme pionniers; elles s'installent après l'établissement de Lupinus d'abord sur des branches tombées (mortes).Les formes biologiques des différentes Bryophytes et leur résistance contre le desséchement ont été étudiées en rapport avec les types de végétation.Les spores des Mousses sont parfois apportées de très loin, mais dans le territoire même qui a été etudié la dispersion végétative par accroissement et par des parties détachées des touffes joue un grand rôle.Quelques expériments avec des carrés de différente surface montrent que la forme des surfaces étudiées est de peu d'importance pour l'étude bryosociologique.Même la litière épaisse sous le couvert du Pin ne retarde pas le développement des Mousses. Les Hépatiques apparaissent les premiers, suivies des Mousses acrocarpes et ensuite des Mousses pleurocarpes.Les Bryophytes corticoles forment une unité à part. On a discerné en tout quatre groupements, trois groupements terrestres et un groupement corticole. Un des trois groupements terrestres constitue probablement un stage de développement tandis que deux autres semblent être des groupements terminaux permanents: stades terminaux l'un pour la brousse à Leptospermum, l'autre pour la forêt littorale.

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This work was carried out by the author while staying at the Auckland University College, New Zealand.     

Two new genera and twelve new species of Anthuridea (Crustacea: Isopoda) from off the West Coast of New Zealand

Abstract

From the shelf and upper slope off the West Coast of the South Island of New Zealand, the following new taxa of Isopoda Anthuridea (Crustacea) are described: Kupellonura proberti n. sp. (Hyssuridae); Quantanthura pacifica n. sp., Haliophasma platytelson n. sp. and H. novaezelandiae n. sp. (Anthuridae) Albanthura stenodactyla n. gen. et sp., A. rotunduropus n. sp., Bullowanthura crebrui n. sp., Leptanthura tmncatitelson n. sp., L. exilis n. sp., L. profundicola n. sp., Paranthura longa n. sp., and Psittanthura egregia n. gen. et sp. (Paranthuridae). Most of these are blind, unpigmented species, adapted to life in deep water. Albanthura n. gen. is blind, has a single telsonic statocyst, short flagella of the antennae, a maxilliped with 3 palpal articles, and a triangular carpus on pereopods 4 to 7. Psittanthura n. gen. is also blind, with very unusual, enlarged subchelae of pereopods 1 and 2, a large, rectangular telson with a single statocyst; the maxillipedal palp is composed of 1 large and 1 small, distal article; a mandibular palp is absent.     

Benthic faunas of streams of low pH but contrasting water chemistry in New Zealand

Water chemistry and benthic invertebrate communities were investigated at 37 sites on acid streams originating on the Stockton-Denniston Plateau, North Westland, New Zealand. The region is characterised by high rainfall and runoff, highly acidic soils and the presence of extensive coal measures that have been mined for over 120 years. Four groups of streams were identified: naturally acid plateau streams with clear water and very low conductivity; brown water (humic) streams with pH<4 and low conductivity; coastal plains streams with higher pH and conductivity; and streams contaminated by acid mine drainage. TWINSPAN and cluster analysis also grouped streams into four groups based on presence-absence of invertebrate taxa, the groups being similar to, but not identical to those based on physico-chemical factors. Diptera (mainly Chironomidae) were represented by most species in all site groups followed by Plecoptera in plateau streams, and Trichoptera on the coastal plain and where mine drainage occurred. Species of Orthocladiinae (Chironomidae), Plecoptera and Trichoptera were found at the most contaminated sites (pH <3, conductivity >900 µS cm^–1, total reactive aluminium >25 mg 1^–1). The leptophlebiid mayfly Deleatidium was found at 32 of the 37 sites, and some species of Plecoptera, Trichoptera and Chironomidae were also widely distributed. Our findings indicate that species tolerant of low pH (i.e., <4.5) are not confined to humic waters as has been postulated, but also occur in soft, non-humic waters where concentrations of labile, non-organically bound aluminium may be elevated.     

Population density and geographical range size in the introduced and native passerine faunas of New Zealand

The current avifauna of New Zealand comprises species with two distinct origins: those that evolved in New Zealand or colonized naturally from neighbouring landmasses, and those that were deliberately introduced to the islands by European settlers. Elsewhere, it has been shown that for species introduced to New Zealand from Britain there is a positive interspecific correlation between the geographical range sizes attained in both countries. Since positive relationships between abundance, measured either as population size or density, and geographical range size are a near ubiquitous feature of assemblages of closely related animal species, this suggests that species’ abundances may also be so correlated between the two countries. Here, data for 12 passerine bird species introduced to New Zealand from Britain are used to compare population densities and density–range size relationships in their native and alien ranges. In addition, the density–range size relationship for 12 passerine bird species that can be considered native to New Zealand is compared to that for the introduced species. The geographical range size and the mean and maximum densities of introduced species in New Zealand were significantly positively correlated with those values for the same species in Britain. However, in no case was the relationship between mean density and range size significant. While not statistically significant, density–range size relationships for introduced species are similar in New Zealand and Britain, but those for introduced and native species in New Zealand are quite different. Implications of these patterns are discussed.     

Landscape‐scale life‐history gradients in New Zealand freshwater fish

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Length–weight relationships of 33 fish species from New Zealand

Length–weight relationships are presented for 33 fish species from New Zealand. The parameters a and b of the equation W = aL^b were estimated. Parameter b ranged from 2.51 (Pseudocaranx dentex) to 3.51 (Alepocephalus antipodianus) with a mean of 3.12 ± 0.24. Most of these estimates (90.9%) were between 2.8 and 3.4. Maximum lengths and depths of catch are updated for nine species.     

The ecology of rivers with contrasting flow regimes: identifying indicators for setting environmental flows

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Mountain streams in Westland, New Zealand: benthic ecology and management issues

1. The West Coast of the South Island, New Zealand (Westland) is a region of mountains, forests, high rainfall, and a history of exploitation. The Southern Alps rise to over 3000m in the east of the region, and a narrow coastal plain supports some agriculture and the main centres of population. 2. Stream waters in the Southern Alps are characterized by low concentrations of major ions, and most can be described as calcium—sodium—bicarbonate waters. Brown waters with low pH and high concentrations of dissolved organic carbon are common at low and intermediate altitudes. 3. Many mountain streams and rivers provide physically harsh environments for aquatic biota with their rapidly changing flows and frequent spates. Hydrological factors and low nutrient concentrations limit periphyton standing crops, and biomass of coarse detritus is often low. Invertebrate populations are usually dominated by insect larvae that feed primarily on FROM and stone surface biofilms. 4. Features of the macroinvertebrate stream fauna on the West Coast are the wide range of physicochemical conditions tolerated by many common species, and the numerical dominance of the mayfly Deleatidium (Leptophlebiidae) in many streams. The Plecoptera also exhibit high diversity relative to other parts of the country, and an unusual trend towards terrestrialism is shown by larvae of Gripopterygidae. 5. The West Coast has a long history of coal and gold mining, forestry and farming, activities that have had negative impacts on stream communities and water quality. We discuss some ecological and management issues associated with present day mining practices, and a proposal to take large volumes of alpine stream water for export.