Past and present benthic fauna of Lake Maratoto with special reference to the chironomidae

The benthic fauna of Lake Maratoto, a eutrophic dy (dystrophic) lake in the Waikato basin, was investigated from 19/9/78 to 13/3/80. Core samples were taken at approximately fortnightly intervals from six stations of varying depths. Fifty taxa were recognised and the distribution and seasonal abundance of the 20 major ones is given together with notes on their biology. A major emphasis was placed on Chironomidae which, after oligochaetes, were the most numerous benthic macroinvertebrates encountered. The fauna had a clumped distribution and was concentrated on the edge of the lake. This was due to higher food supplies and more diverse sediment types on the edges and anoxic conditions in the centre. Some re-distribution of the fauna occurred during periods of wind turbulence but planktonic activity in the Chironomidae was of short duration. The annual mean standing crop of chironomid larvae was 2970 per sq. m. This was made up of 40% Calopsectra funebris, 37% Chironomus zealandicus, 5% Kiefferulus opalensis, 5% Tanypodinae, and 1% Podonominae and Orthocladiinae. Photographs of some of the distinguishing features of the chironomid taxa identified are given as well as measurements for separating larval instars. Recruitment in the chironomids was continuous but with periods of increased rates. Species with dissolved haemoglobin in the blood (e.g. Chironomus zealandicus and Cladopelma curtivalva) increased in numbers during the summer, while in winter, species which lacked this trait e.g. Calopsectra funebris were more abundant. Lowest numbers were recorded in the spring. It is hypothesised that increases in larval numbers are linked to algal production and eventual sedimentation of autochthonous organic matter. Principal component analyses were used to predict the limnological characteristics of a lake from knowledge of its surficial sediment chironomid remains. Dystrophic lakes were characterised by high numbers of most species, particularly Kiefferulus opalensis, Tanypodinae, Calopsectra spp. and Paucispini gera spp. but low numbers of Paratanytarsus a gameta. Clear lakes had proportionally more Corynocera sp. and Cladopelma curtivalva while lakes which were dominated by Paratanytarsus agameta, Orthocladiinae and Polypedilum spp. were productive and/or turbid. The developmental history of Lake Maratoto . since its formation 17,000 years ago was studied by analysis of chironomid remains from a 4 m sediment core. Numbers of fossils were low initially but climatic improvement about 14,000 yr B.P. led to an increase which culminated at 5,000 yr B.P •. Peat, which began to develop close to the lake about 12,000 yr B.P. had significant effects in the top section of the core, with maximum influence on the fauna about 7,000 years ago. Other changes in the core were largely expressions of climatically controlled fluctuations of water level which altered the area of the littoral zone. Twelve stratigraphic zones of chironomid microfossils were derived from cluster and multiple discriminant analyses. These are discussed in relation to zones derived from pollen, stratigraphy and chemical analyses of the sediment

Stratigraphy and chronology of late Quaternary tephras in Lake Maratoto, Hamilton, New Zealand

A 3 m piston core from Lake Maratoto (37°53’S 175°18’E) near Hamilton shows at least 12 thin, well-preserved distal airfall tephras intercalated with humic copropel (dy) deposits. Most of the tephras have been identified by their dominant ferromagnesian mineralogy, their stratigraphic position, and 5 radiocarbon dates. The majority of the tephras are derived from the Taupo and Okataina Volcanic Centres, while others originate from Mayor Island, Tongariro, and possibly Mount Egmont sources. The tephras dated (Libby ages) are: Taupo Pumice (Wk215) 1730 ± 60 years B.P., Tuhua Tephra (Wk214) 6210 ± 70 years B.P., Mangamate Tephra (Wk213) 10 120 ± 100 years B.P., and Rerewhakaaitu Ash (2 dates) (Wk237) 14 700 ± 220 years B.P. and (Wk238) 14 700 ± 180 years B.P. The identification of the tephras in Lake Maratoto extends the previously mapped distribution of North Island post-glacial (Holocene) tephras, and complements studies of soil genesis and weathering in the Waikato region. The core also provides a geochronological basis for further multidisciplinary studies of the paleolimnology, paleoclimate, and sedimentological history of the region

Age and growth of longfinned eels (Anguilla dieffenbachii) in pastoral and forested streams in the Waikato River basin, and in two hydro-electric lakes in the North Island, New Zealand

Growth rates of New Zealand endemic longfinned eels (Anguilla dieffenbachii) from streams in pasture and indigenous forest, and from two hydroelectric lakes (Lakes Karapiro and Matahina), were estimated by otolith examination. Habitat-specific growth was further investigated with measurement of widths of annual bands in otoliths. Longfinned eels 170-1095 mm in length ranged between 4 and 60 years old (N=252). Eels in pastoral streams grew faster (mean annual length increment ±95% CL = 24 ± 3 mm to 36 ± 7 mm) than eels in streams in indigenous forest (annual length increment 12 ± 2 mm to 15 ± 3 mm). Eels from the hydro-electric lakes had growth rates (annual length increments 19 ± 4 and 19 + 7 mm) similar to eels from pastoral streams. Otoliths of most eels showed annual band widths that indicated growth in several different habitats, corresponding to growth during upstream migration, and limited movement among adult habitats. Estimated age at marketable size (220 g) ranged between 7 and 26 years. The particularly slow growth of longfinned eels in streams in indigenous forest has considerable implications for management. The fast growth rates of eels in hydro-electric lakes provides evidence for the potential of increased eel production by stocking. The probable selective production of female eels in these lakes may be nationally important to allow enhancement of breeding stocks

Gravel-lined upstream fish passes: Construction guide

Prepared for the Department of ConservationNone supplied. Introduction: Continuing pressures on many of New Zealand's native freshwater fish species has seen a substantial decline in their numbers. This decline has serious implications for New Zealand, both economically and ecologically. Several of the freshwater species (primarily eels and whitebait) generate sizeable revenue, while any decline in the fish populations, which are part of our natural heritage, affects the richness and diversity of New Zealand's fauna. Most of New Zealand's native freshwater fish are diadromous; this is they are obliged to migrate between the sea and freshwater to complete their life cycles. Many make extensive upstream migration as juveniles. These young fish are generally poor swimmers who make use of low-velocity zones on the edges or bottom of rivers and streams to make their way upstream. Some species have evolved climbing abilities that enable them to surmount waterfalls and rapids. The gravel-lined fish pass described in this guide capitalises on this behaviour

Gravel-lined upstream fish passes: Construction guide

None supplied. Introduction: Continuing pressures on many of New Zealand\u27s native freshwater fish species has seen a substantial decline in their numbers. This decline has serious implications for New Zealand, both economically and ecologically. Several of the freshwater species (primarily eels and whitebait) generate sizeable revenue, while any decline in the fish populations, which are part of our natural heritage, affects the richness and diversity of New Zealand\u27s fauna. Most of New Zealand\u27s native freshwater fish are diadromous; this is they are obliged to migrate between the sea and freshwater to complete their life cycles. Many make extensive upstream migration as juveniles. These young fish are generally poor swimmers who make use of low-velocity zones on the edges or bottom of rivers and streams to make their way upstream. Some species have evolved climbing abilities that enable them to surmount waterfalls and rapids. The gravel-lined fish pass described in this guide capitalises on this behaviour

Eel protection measures within the Manapouri hydro-electric power scheme, South Island, New Zealand

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Optimizing the flow pattern in culverts for small upstream migrating fish using a numerical 3D Code

2037-204

Matahina Dam Elver Pass Development, Installation, and Fisheries Aspects

None supplied. From summary: The pass componentry and location on the structure which had been determined prior to the 1990/91 elver season, was installed in early 1991. Between the end of this season and the 1991/92 season refinements to the pass were made to both security and function. Fluctuating lake levels, along with installation of automation equipment showed the demand for a second water supply to combat loss of water. The entry to the pass at the tailrace on the left hand side of the power house has attracted elvers. Some elvers also climb the spillway step and wall and continue on up the pass. However, elvers still gather at the transformer cooling water outlet on the right bank, and also on the draft tube stoplog platform. Elvers have no difficulty in climbing the troughs and pipes and drainage channels, and hence the pass is readily passable to these juvenile fish, and is working as intended. The success overall will be to have the pass without competition from the other collection points around the station. Several hundred climbing Galaxiid juveniles (whitebait) and at least 15,000 elvers used the pass in the summer of 1991/92. The elver migration began in mid January 1992, peaked on the full moon in January and ended soon after new moon in early March. Maximum migration occurred around midnight and was lowest during daylight hours. The number of elvers using the pass could have been several fold higher had the water supply to the pass been reliable