Conservation status of New Zealand freshwater fish, 2009

Abstract

The threat status of 74 freshwater and estuarine fish present in New Zealand was determined. Fifty-one native taxa were ranked of which 67% were considered Threatened or At Risk. A single species was classified as Extinct, the New Zealand grayling, which has not been observed since the 1920s. Four taxa were classified in the highest threat category, Nationally Critical, and a further 10 taxa as Threatened (Nationally Endangered or Nationally Vulnerable). Twenty taxa were ranked in the At Risk group with the majority ranked as Declining. Endemic galaxiids (Galaxiidae) dominated the Threatened and At Risk taxa. The majority (68%) belonged to the Galaxias genus, comprising 81% of recognised taxa in this genus and all five species in the genus Neochanna were also ranked as Threatened or At Risk. In addition to 51 native taxa, a further three fish species were considered colonists and 20 introduced species were classified as naturalised, although two of these are considered rare. The majority of the Threatened species occur in the Canterbury and Otago regions where a suite of rare non-migratory galaxiids exist. Threat mechanisms that were identified as causal in the decline of freshwater fish species were the impact of introduced fish species, declining water quality, effects of water abstraction, loss of habitat via land-use change and land-use activities, and river modifications.

Re: Conservation status of New Zealand freshwater fish, 2009; Allibone et al. (2010)

“…These trends in eel populations have been supported by recruitment data (Martin et al 2008) also supplied to Allibone et al (2010). Martin et al (2008) concluded that longfin eel recruitment was quite variable, but 'since about 2000Á01, annual recruitment of longfin elvers, although variable, has tended to increase'.…”

“…Instead, they rely on the work of Jellyman (2009), who describes the past historic decline in eel populations, but does not analyse more recent data in any detail. Allibone et al (2010) then conclude that '. .…”

“…I have attempted to ascertain the reason(s) why Allibone et al (2010) would classify a species (the longfin eel) as 'declining', when two separate monitoring methods, using the most recent data, indicate the opposite. Their article (p. 285) correctly explains that there is a level of uncertainty with using recruitment data alone as a reliable method for monitoring eel populations.…”

“…Basic catch records exist for a longer (Â40-year) period, although these latter data are of variable accuracy. Prior to publication, Allibone et al (2010) were supplied with CPUE data for the period 1991Á2006 (Beentjes & Dunn 2008). This report concludes:…”

“…Declining', based on the threat ranking system described in Townsend et al (2008). Allibone et al (2010) based their classification on the threat ranking system 'Status Criteria C2', which requires the following population characteristics:…”