TANE 27, 1981 NOTES ON THE STREAM MACROFAUNA OF CUVIER ISLAND by David J. Riddell Department of Zoology, University of Auckland, Private Bag, Auckland SUMMARY An annotated list of the animal species collected from the Pumphouse Stream, Cuvier Island is given. Insects, particularly Trichoptera, comprise most of the species, although the gastropod Potamopyrgus antipodarum was the most abundant species present. Reasons for the rather impoverished state of the fauna are discussed. INTRODUCTION Only one significant catchment exists on Cuvier Island. Through this runs, in an east-west direction, the Pumphouse Stream, named after the old pumphouse which stands near its source (see fig. 1, Wright 1981). The flow rate is very low (about 1 litre/sec at the time of study), but the stream has a well-formed rocky course and gives every indication of being permanent. A few other gullies had water trickling through them at the time of the Field Club visit, but none of these are likely to be permanent. 'H' Gully, however, had several deep-shaded pools in its lower reaches which could well retain (somewhat stagnant) water throughout the year. In 1964, J. Robb collected larvae of two species of caddis fly, Polyplectropus puerilis, and Pycnocentria funerea from Cuvier Island (Cowley 1978). As far as I know these represent the only previous freshwater collection from this locality. MATERIALS AND METHODS The low flow-rate precluded quantitative methods such as the use of a Surber sampler. Samples were taken by washing and picking animals off rocks into a hand net (1 mm mesh), then transferring them to jars containing 10% formalin. Where present, sticks and weed were also checked for animals, and a general search was made of each area for any obvious animals which may have been missed by these methods. Approximately equal effort was allocated to each of the eight sites. Sampling sites covered the length of the stream from the sea to the pumphouse, and covered as wide a range of habitats as possible, namely falls, pools and regions of slow flow, both in the bush and in the 33 open broad coastal strip. 'Falls' were only 1-2 m in height and supported thick growths of moss (bush falls) or moss and filamentous algae (coastal falls). Considerable amounts of silt had accumulated around the rocks in the bottoms of the pools. The results are presented in the following species list. SPECIES LIST PHYLUM CNIDARIA Class Hydrozoa Order Gymnoblastea Family Cordylophoridae Cordylophora lacustris Allman One colony was found in a pool near the sea. PHYLUM PLATYHELMINTHES Class Turbellaria Order Tricladida Family Planariidae Cura sp. This heavy-bodied planarian, lacking auricles, was rather uncommon, but was found in slow-flowing stretches throughout. PHYLUM MOLLUSCA Class Gastropoda Order Mesogastropoda Family Hydrobiidae Potamopyrgus antipodarum (Gray) Collected at all but one of the sites, this ubiquitous species dominated the fauna in all habitats except falls, where it was less common. PHYLUM ARTHROPODA Class Crustacea Order Amphipoda Family Eusiridae Paracalliope fluuiatilis (Thompson) Abundant in coastal pools, and present at all sites except the two falls. Class Insecta Order Ephemeroptera Family Leptophlebiidae ?Zephlebia spp. At least three species of this taxonomically difficult family are present, only one of which is common. It was found at all sites except the coastal fall. Order Neuroptera Family Corydalidae Archichauliodes diversus Walk Common throughout under stones. Order Trichoptera Family Rhyacophilidae A single unidentified specimen belonging to this family was found in a slow-flowing region near the sea. Family Sericostomatidae Pycnocentria funerea McLachlan Present throughout, but more common in the bush. Olinga feredayi (McLachlan) Common in all habitats near the sea, this species was also collected in low numbers from a bush pool. Family Centropodidae Polyplectropus puerilis (McLachlan) Moderately common throughout in pools and slow-flowing regions. Family Hydropsychidae Orthopsyche fimbriata (McLachlan) Present at the two falls sites in low numbers. Order Diptera Family Chironomidae Large numbers of small green larvae and pupae were present at the coastal falls, 34 although elsewhere only three were collected (from the pumphouse site and a coastal pool.) Family Dixidae One specimen belonging to this family was found in a silty-bottomed slow-flowing stretch near the sea. These animals are easily overlooked and could well be more common. PHYLUM CHORDATA Class Osteichthyes J. McCallum (pers. comm.) reports the presence of eels (Anguilla spp.) in this stream, although none were seen during this study. The habitat appeared suitable for bullies (Gobiomorphus cotidianus McDowall and G. huttoni (Ogilby)), but a brief search for them was unsuccessful. DISCUSSION The number of species collected from the Pumphouse Stream is low. While this may in part be a reflection of the low number of samples taken, the fauna of this stream is indeed rather impoverished. The small volume of water and low flow-rate would seem to be most responsible for this. Several species encountered in swifter waters are absent: notably stone-flies (Plecoptera), the spiny-gilled mayfly (Coloburiscus humeralis) and the sandfly (Austrosimulium sp.). The latter two species require a fairly strong current to filter their food, while Pendergrast and Cowley (1969) state that the former "prefer those regions where there is a reasonable amount of water flow." Such regions are few and far between in the Pumphouse Stream and it is quite possible that these animals are indeed absent. One filtering species, Orthopsyche fimbriata, however, manages to survive here, although it is rather rare. Its very presence, however, indicates that there is probably always at least some water flow, and therefore complete drying out of the stream must be rare indeed, if it occurs at all, and so could not have a major influence on the species present in the fauna. Neither does the isolation of this habitat seem to be of major significance. Adult Archichauliodes diversus are short-lived and poor fliers (Pendergrast and Cowley 1969), yet even they have managed to cross the thirty-odd kilometres of open sea from the nearest stream. The species which are present are generally either abundant and widespread animals, such as Potamopyrgus antipodarum and Paracalliope fluviatilis (Marples 1962), or species typical of small streams, e.g. Pycnocentria funerea and Orthopsyche fimbriata (Cowley 1978). The colonial hydroid, Cordylophora lacustris, is perhaps the most rarely encountered species. Marples (1962) records it as occurring in the lower reaches of slow rivers and streams, as is the case here. He lists only two localities, Dunedin (several sites) and the Esk River, Napier, although he, apparently correctly, assumed it to be more widespread. 35 ACKNOWLEDGEMENTS I would like to thank Dr D.R. Cowley for assistance in finding references, and everyone who went to Cuvier Island for making the week so enjoyable. REFERENCES Chapman, M.A. & Lewis, M.H. 1976: "An Introduction to the Freshwater Crustacea of New Zealand." Collins, Auckland and London. 261 p. Cowley, D.R. 1978: Systematic studies on the larvae of New Zealand Trichoptera. New Zealand Journal of Zoology 5(4): 639-750. McFarlane, A.G. 1951: Additions to the N.Z. Rhyacophilidae. Records of the Canterbury Museum 5(5): 255-266. McFarlane, A.G. 1951: Caddis Fly Larvae of the family Rhyacophilidae. Records of the Canterbury Museum 5(5): 267-289. Marples, B.J. 1962: "An Introduction to Freshwater Life in New Zealand." Whitcombe and Tombs, Christchurch. 160 p. Pendergrast, J.G. & Cowley, D.R. 1969: "And Introduction to the Freshwater Insects of New Zealand." 2nd edition. Collins, Auckland and London. 100 p. Phillips, J.S. 1930: A revision of the New Zealand Ephemeroptera. Transactions and Proceedings of the New Zealand Institute 61: 271-390. Towns, D.R. & Peters, W.L. 1979: Three new genera of Leptophlebiidae (Ephemeroptera) from New Zealand. New Zealand Journal of Zoology 6(2): 213-235. Wright, A.E. 1981: Auckland University Field Club scientific trip to Cuvier Island, May 1980. Introduction and Acknowledgements. Tane 27:1-6. 36 .