NIWA Water & Atmosphere 11(2) 2003

FRESHWATER FISH Location, location, location! Predicting fish communities in streams

The waterways pictured opposite represent a Zealand. We selected quantitative data range of typical New Zealand streams. Can (collected using electric fishing) because we we predict the resident fish community from thought the most abundant fish species – and Jody Richardson just a photograph? The results of our recent not those that just occur by chance – should Ian Jowett analysis of data from the New Zealand define a community. Our 1130 sites were freshwater fish database suggest that we can, therefore mainly small and medium-sized but first we need more information, wadeable waterways. We excluded fish particularly about the stream’s location. communities from deep-water and/or still- What is a fish community? water habitats unsuited for electric fishing. We combined the fish data with site A fish community is an assemblage of fish information such as location, stream width species that inhabit a particular area of a and catchment land use. The first stage of the stream or river. Based on 40 years of analysis was to use a computer program to Can you tell accumulated field sampling, we now know classify sites by their fish assemblages into that certain fish species commonly occur which fish biologically sensible groups. We then together whereas others don’t. This is usually examined the results to see whether the communities related to their preferred habitat and, for communities matched our experience and inhabit the diadromous species (that spend a part of their intuitive definitions. streams in the life-cycle at sea), their ability to penetrate inland. For example, open-bed, fast-water Most of the groups identified by computer photographs? species such as torrentfish and bluegill bully analysis were immediately familiar to us. For Read on – and are often found together, but are practically example, upland and lowland fish then try our test! never found with pool-dwelling bush species communities were clearly separated. We such as adult banded kokopu. Thus, we would defined 12 fish communities, though many expect a torrentfish community to inhabit species occurred in several of these. quite different types of waterways from a Environmental information for banded kokopu community. predicting communities But why bother with fish communities? After each site had been assigned to a fish Water management decisions often focus on community, we then used the differences in single valuable or threatened fish species, but the site locations and physical characteristics Teachers: this usually rivers contain a whole community of to develop our models for predicting fish article can be used fish. Knowing what species occur together communities. for NCEA and in what types of waterways can help Achievement Geographic location was the over-riding Standards in managers predict the effects of flow and land factor influencing fish communities. The Biology (1.2, 2.2, management options on the whole 2.5, 2.6, 3.4). See distribution of many of the communities community. This approach not only protects other curriculum depended on whether the fish were connections at individual species and biodiversity, but also diadromous or not, and the ability of the www.niwa.co.nz/ helps identify appropriate restoration and pubs/wa/resources diadromous species to penetrate inland. conservation strategies for a particular Altitude showed the most difference between waterway. communities, closely followed by distance Defining fish communities inland. We used an analysis of the New Zealand Habitat was a less obvious factor but was Freshwater Fish Database (NZFFD) – plus important for some fish species. For example, experience – to describe common fish banded kokopu were typically found in small Jody Richardson and communities and to determine their predict- streams (average width 1.6 m), whereas Ian Jowett are based ability. The NZFFD contains information on torrentfish occurred in wide streams (average at NIWA in Hamilton. freshwater fish from sites throughout New width 10.5 m).

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Overall, our best predictive model used a Species composition (average %) of the 12 fish communities. Blue numbers combination of five location variables (altitude, highlight up to six of the most abundant fish in each community. distance inland, northing, island, easting), three Fish communities catchment vegetation variables (farming, native, exotic forest), and stream width. Some communities were easier to identify

Shortjaw kokopu

Banded kokopu

Redfin bully

Shortfin eel

Inanga

Torrentfish

Crans bully

Upland bully

Koaro

Brown trout

Rainbow trout

Longfin eel and predict than others. For example, more Fish species Shortfin eel 0.0 4.8 0.9 28.1 8.2 2.3 15.3 5.3 0.0 0.4 0.3 0.0 than half of the koaro, inanga, Crans bully, Longfin eel 26.0 15.1 28.7 14.3 10.2 22.2 18.3 12.6 18.0 11.6 11.3 90.4 upland bully, and rainbow trout communities Torrentfish 0.0 0.0 0.5 4.9 0.0 18.4 1.7 0.3 0.1 0.5 0.1 0.0 13.0 1.0 0.0 0.2 0.0 0.2 0.1 0.0 0.0 0.0 0.0 0.0 could be successfully predicted from the Koaro 19.0 3.3 4.8 0.1 0.3 0.7 0.0 8.0 64.7 1.2 2.9 0.0 environmental variables, whereas less than a Dwarf 0.0 0.3 0.0 0.0 0.0 0.1 0.0 5.3 0.2 0.6 0.0 0.0 fifth of longfin eel and Banded kokopu 0.7 53.3 4.2 0.5 0.4 0.0 0.0 0.0 0.5 0.0 0.1 0.0 Inanga 0.0 9.5 1.9 2.6 52.4 2.0 0.6 0.8 0.3 0.6 0.0 0.0 communities could. The lowland communities Alpine galaxias 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.3 0.0 0.3 2.1 0.0 characterised by redfin bully, torrentfish and Shortjaw kokopu 17.2 0.0 0.6 0.0 0.1 0.1 0.0 0.1 0.5 0.0 0.0 0.0 Canterbury galaxias 0.0 0.0 0.0 0.0 0.0 0.3 0.0 10.6 0.0 0.3 0.1 0.0 shortfin eel were also difficult to classify Lamprey 0.0 0.2 1.3 4.8 0.1 0.2 0.3 0.4 0.2 0.7 0.0 0.5 consistently. Crans bully 0.0 0.1 0.0 0.0 0.3 0.1 59.9 3.7 0.4 0.7 0.6 0.0 Upland bully 0.0 0.0 0.0 2.4 0.0 3.7 0.0 43.1 0.0 5.9 0.5 0.0 The communities Common bully 0.0 0.2 2.2 7.0 13.8 9.1 0.0 0.5 0.1 1.4 0.8 9.1 Bluegill bully 20.7 0.0 8.7 5.0 0.1 25.0 0.0 0.5 0.6 0.3 0.0 0.0 We generally named the communities after Redfin bully 2.4 11.8 43.8 23.9 13.8 12.6 0.2 1.2 2.4 1.3 0.3 0.0 their dominant fish species. Smelt 0.0 0.0 0.0 4.6 0.1 0.1 3.4 0.3 0.0 0.0 0.0 0.0 Rainbow trout 0.0 0.1 1.2 0.2 0.0 0.4 0.1 0.2 1.2 2.0 74.4 0.0 Banded kokopu, shortjaw kokopu, redfin bully Brook trout 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.4 0.0 0.0 The characteristic species of these three Brown trout 1.0 0.0 1.2 1.4 0.3 2.3 0.2 4.6 11.0 71.0 6.3 0.0 communities were found living together, as well as with longfin eel and koaro. The Plenty, Coromandel, Waikato and Auckland preferred habitat was small bush-covered regions. South Island locations were on the streams. All were associated with native forest west coast, in the Catlins, Otago and Banks (more than 60% of the catchment) and a low peninsulas and Marlborough Sounds. Shortjaw Photos: percentage of farming development (less than kokopu communities were mainly found in A: a tributary of the 22% of the catchment). rivers draining to the south Taranaki Bight, Waikato River near Huntly. The catchment Banded kokopu community streams were the Golden Bay and the Marlborough Sounds. is 100% native bush smallest (1.6 m wide) and had the highest Redfin bully communities were widely and the stream is 1–2 m wide. Although over percentage of pool habitat. Location was scattered but were very rare on the east coast 100 km inland, the site distinctly coastal, but throughout the Bay of of either island. is only 20 m above sea level, and there A B are no barriers to migration. B: a medium-sized, low-gradient river in Northland. The catchment is mostly farmland and the riverbed is mud. This site is 22 km inland with an altitude of 50 m. C: a medium-sized, relatively steep river in North Canterbury. The site is only a few km C D inland at low altitude. The catchment is about 90% farmland. D: a lake-fed river in the central North Island. It is 20 m wide and there is a large waterfall downstream. The site is high (300 m) and well inland (64 km) with a mixed catchment of exotic forest, native bush and farming.

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Inanga, shortfin eel, torrentfish often at high elevations. In the North Island, These three communities also had a similar the koaro communities occurred south of a species assemblage, including relatively high line between East Cape and Taranaki, but not densities of the diadromous bully species. on the east coast south of Hawkes Bay. In the They were usually found at lower altitudes South Island, koaro communities were mainly than the previous three communities. Inanga confined to the west coast, Southland and communities were confined to very low Otago. altitudes, with none found farther than 50 km Brown and rainbow trout communities inland. They were rare in northern New Trout communities occurred at high Zealand. elevations and were generally farther inland Sites with shortfin eel communities occurred than any of the other groups. The brown trout in farmed catchments rather than native bush community was the largest group identified and were associated with mud streambeds. and was widespread except in the northern Most occurred in the North Island, perhaps part of the North Island, where warm winters reflecting this species’ preference for relatively inhibit successful egg development. warm water. Rainbow trout communities were restricted to Torrentfish inhabit riffles in open riverbeds. the central North Island and a few sites Sites with this community had the highest associated with large inland lakes in central average stream width of all the groups, and a Otago. A previous study found that brown low percentage of pool habitat. The torrentfish and rainbow trout communities tended to community had the highest average density inhabit places with different kinds of water of bluegill bullies, which also prefer a riffle flow. In particular, rainbow trout communities habitat. Torrentfish communities occurred were associated with lake- and spring-fed equally in the North and South Island, but rivers with stable flows, such as those in the generally at low elevations and not very far central North Island. The low percentage of inland. farming land use in the site catchments Crans bully community probably reflects the location of most lake catchments in unfarmed areas. The non-diadromous Crans bully occurs only in the North Island, but not in the Bay of Longfin eel community Plenty or East Cape where its extinction is Longfin eels are ubiquitous and were usually thought to be due to the Taupo eruptions. the most abundant or second most abundant Crans bully communities contained mainly species in any community. Their climbing Crans bully and eels, and occurred at lower ability allows them to gain access to the average elevations than the other non- headwaters of most New Zealand rivers and diadromous communities. However, the sites they are absent only from some rivers in the were well inland, particularly in the low- central North Island. Sites classified as gradient Manawatu and Wanganui containing longfin eel communities were well catchments. The communities occurred across inland at high altitudes, beyond the reach of all land uses and tended to inhabit wide other diadromous species. It was very difficult streams with a high percentage of pools. to predict these locations, because we had no Upland bully community information on the presence of waterfalls or rapids that might be a barrier to the passage Upland bullies do not occur north of Lake of other fish species. Taupo, in northwest Nelson, or on the west coast of the South Island south of the Hokitika Can you predict the fish River. Nevertheless, this group was second community? largest, occurring at moderate altitudes and Now that you have been given some distances inland. Some of the less common information about the fish communities and non-diadromous galaxiid species, including their environmental characteristics, read the dwarf, alpine and Canterbury galaxias, were photo captions for some details about the found in this community. location of the streams shown. Try to guess Koaro community which community it contains based just on Koaro community streams had the highest this information and the picture. We think you average percentage of native forest (90%) and will find it can be done! The answers are on usually contained cascade habitat. They were page 27. I

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