Jody Richardson

Microhabitat preferences of benthic invertebrates and the development of generalised Deleatidium spp. habitat suitability curves, applied to four New Zealand rivers

Microhabitat preferences of 12 benthic invertebrate taxa were investigated in four New Zealand rivers. Most taxa showed significant habitat preferences. Generally, taxa were more abundant in water ...

Microhabitat preferences of benthic invertebrates in a New Zealand river and the development of in-stream flow-habitat models for Deleatidium spp.

Abstract Microhabitat preferences of seven groups of New Zealand benthic invertebrates (Deleatidium spp., other mayflies, cased caddisflies, uncased caddisflies, beetles, Diptera, and stoneflies) were investigated and habitat suitability functions for use with the instream flow incremental methodology (IFIM) developed for the predominant group, Deleatidium spp. All invertebrate groups except uncased caddisflies and Deleatidium spp. exhibited significant preferences for at least two of the three habitat variables (substrate, water velocity, and depth) when each habitat variable was considered independently. Significant relationships were found between invertebrate size and at least one habitat variable for all groups except stoneflies. Models of Deleatidium spp. abundance were poor (r = 0.50–0.58) and generally predicted biomass better than numbers. The best models used all three habitat variables together with an index of the amount of periphyton. Deleatidium spp. abundance in the Waingawa River was most ...

Habitat preferences of common, riverine New Zealand native fishes and implications for flow management

Abstract Habitat use of eight native fish species was determined by electroshocking depth‐stratified lanes < 0.125 m, 0.125–0.25 m, 0.25–0.5 m, and 0.5–0.75 m. Two runs and two riffles were sampled in 34 rivers. Water depth, velocity, and substrate size were measured. Bluegilled bullies (Gobiomorphus hubbsi), upland bullies (G. breviceps), common bullies (G. cotidianus), longfinned eels (Anguilla dieffenbachii), and shortfinned eels (A. australis) made up over 80% of the total number and biomass of fish sampled. Overall, fish densities were highest along river margins in depths of less than 0.25 m, and higher in riffles than in runs. The fish species could be classified into four habitat guilds: a fast‐water guild that occupied central portions of riffles, an edge‐dwelling guild, an intermediate guild, and finally a guild that was ubiquitous. Minimum flow requirements based on habitat for the edge‐dwelling and fast‐water guilds would be conflicting, with one benefiting from low flows and the other from hi...

Distribution and abundance of freshwater fish in New Zealand rivers

The distribution and abundance of fish at sites in 38 medium to large New Zealand rivers were examined. Fish density varied from 5 to 200 fish per 100 m2, with an average of 53 fish. Our study sites contained a greater species richness and abundance than records stored on the New Zealand Freshwater Fish Database, where the average density was 28 fish per 100 m2. The average number of species at the study sites was 5, compared to 3 in the national database. Comparison of first-pass catches with multiple-pass population estimates showed that there was no difference in capture probability between species and that on average 51% of the population was captured on the first pass. The diadromous habit of many native species, and their ability to penetrate inland, was an overwhelming influence on their distribution. There was little regional variation in species composition, apart from the presence or absence of three non- diadromous species. Two distinct fish communities were evident: lowland and upland. Lowland communities typically contained the highest density and diversity offish, whereas upland communities were dominated by one or two species. Many river sites were intermediate between lowland and upland, both in species composition and fish density, and showed a gradual reduction in abundance and change in community structure with elevation, as those fish less able to penetrate inland disappeared and non-diadromous species began to appear. Elevation was the most important discriminating factor, with physical habitat and

Thermal tolerance and preference of some native New Zealand freshwater fish

Upper lethal and preferred temperatures were determined experimentally for eight common species of New Zealand freshwater fish. Upper lethal temperatures ranged between 28.3 and 39.7°C and preferre...

Relative effects of in-stream habitat and land use on fish distribution and abundance in tributaries of the Grey River, New Zealand

Abstract The distribution and abundance offish was investigated over 2 years at 78 sites in Redjacks Creek and adjacent tributaries draining native, exotic, and mixed forest catchments within the Grey River system, South Island, New Zealand. The abundance of diadromous fish decreased with altitude and distance from the sea, whereas the abundance of non‐diadromous fish species, especially dwarf galaxias (Galaxias divergens), increased with altitude and distance from the sea. Species abundance varied with average stream depth and velocity, generally in accordance with micro‐habitat preferences. The relative influences of diadromy, land use, and physical habitat on fish distribution and abundance were difficult to separate. Differences in fish abundance in the three land‐use categories were often attributable to differences in physical habitat. Nevertheless, there were indications that land use and its effect on the stream environment was influencing the distribution of some fish species. Ammocoetes (Geotria...

EFFECTS OF LAND USE ON NATIVE FISH COMMUNITIES IN EAST COAST STREAMS OF THE NORTH ISLAND OF NEW ZEALAND

The community structure, density, and biomass of native fish species was determined for first‐ to second‐order streams draining mature pine, native forest, and pasture catchments in seven, North Is...

Responses of seven species of native freshwater fish and a shrimp to low levels of dissolved oxygen

Abstract The tolerances of seven New Zealand freshwater fish species and one species of shrimp to low levels of dissolved oxygen were determined in the laboratory by holding fish at dissolved oxygen levels of 1, 3, or 5 mg litre‐1 for 48 h at 15°C. Juvenile rainbow trout (Oncorhynchus mykiss) were also tested for comparison. All of the banded kokopu whitebait (Galaxias fasciatus), juvenile torrentfish (Cheimarrichthys fosteri), adult and juvenile common smelt (Retropinna retropinna), juvenile common bully (Gobiomorphus cotidianus), and trout were dead after 48 h exposure to 1 mg litre‐1. Adult and juvenile inanga (Galaxias maculatus), adult common bully (Gobiomorphus cotidianus), and shrimp (Paratya curvirostris) had mortalities ranging from 27 to 80% at 1 mg litre‐1, whereas all of the elvers (Anguilla spp.) survived. Juvenile rainbow trout were the most sensitive of the species tested, and the only species that had mortalities during exposure to 3 mg litre‐1. No deaths of any fish occurred at 5 mg litre...

Effects of a severe flood on instream habitat and trout populations in seven New Zealand rivers

Abstract The effects of a major flood on instream habitat and trout numbers in 7 rivers in the South Island, New Zealand, were determined by drift diving (snorkeling) sections of each of the rivers before and after the event. A general coarsening of the substrate was noted in runs and pools but not in riffles. In most of the rivers there was significant scouring of pools but little change of run and riffle habitats. In 6 of the 7 rivers, brown trout (Salmo trutta) abundance decreased significantly, with small fish (10–20 cm fork length) being reduced by 90–100%, medium fish (20–40 cm FL) by 62–87%, and large fish (> 40 cm FL) by 26–57 %. Rainbow trout (Salmo gairdneri) occurred in 3 of the rivers but were not present in 2 of these after the flood. In the third river the abundance of largera in bow trout increased substantially whereas that of small fish decreased by 94%. The percentages of trout remaining in the surveyed reaches after the flood were highly correlated with river gradient and instream cover...

Effects of sediment on fish communities in East Cape streams, North Island, New Zealand

Abstract We examined the effects of sediment on fish communities at 38 sites in the East Cape region of New Zealand. Many streams in this region are subject to high sediment loads, a natural situation that has been exacerbated by the conversion of native forest to pasture. The fish community consisted of diadromous native species common throughout New Zealand that require access to and from the sea. We found that site altitude and distance inland were important factors in determining the abundance and composition of the fish community. We used four measures as indices of sediment load: suspended sediment concentration, median substrate size, substrate stability, and the ratio of the wetted width to the width of the active (non‐vegetated) stream channel. Although all indices were correlated, the ratio of wetted width to width of active channel was most closely related to fish abundance and diversity. Fish abundance and diversity reduced as sediment load increased among streams, with up to nine fish species in streams with low sediment loads and only two species in streams with high sediment loads. In‐stream habitat also varied with sediment load; as load increased, depth and substrate size decreased and velocity increased. These results suggest that activities that increase sediment loads in rivers will have a negative impact on native fish communities in New Zealand.