Variability in spatial and temporal abundance of glass eels (Anguilla spp.) in New Zealand waterways

Abstract

The regional and annual variability in the abundance of newly arrived glass eels, Anguilla australis (Richardson) and Anguilla dieffenbachii (Gray), were examined using glass eel densities (n = 100 m^–2) from electric‐fishing samples collected at 14‐day intervals over 5 years from 13 streams/ rivers throughout New Zealand. Although the density of shortfin eels exceeded that of longfin eels for any one year, the annual trends for both species were generally similar. Both species behaved independently, but significant factors affecting density were “year” and “region”, with the pronounced regional effect for longfin eels attributed to “coast” (east or west), but not “island” (north or south). There was no evidence of declining recruitment for longfin glass eels.

Keywords:

• glass eels
• density
• recruitment variability