Samenvatting

The native fish populations in New Zealand have proven to be declining. There are various reasons for this change in population size, one of the biggest being structures that form barriers to migration. This shows the need for fish passage options that are better adjusted to these ‘weaker’ swimmers and their lifecycles (since most of these species migrate in their juvenile stage). Acquiring information about the swimming abilities of these species is critical in order to create fitting solutions. In this paper the swimming endurance of inanga (Galaxias maculatus) is measured. This was done in the form of an endurance test in a swim tunnel.

The purpose of this research is to fill a gap in knowledge about the swimming capabilities of native fish species in New Zealand, in particular inanga. Filling this gap will help with the design of more appropriate fish passage options. The central question in this report is: ‘What is the maximum water velocity in a culvert with a maximum length of 50 meters that will allow 90% of the inanga population to migrate through the structure?’

The gathered results show the importance of not only decreasing fall height, but also adding baffles or other structures inside the culvert itself. These structures reduce water velocities and will create a place where inanga can rest when tired and thus provide a better chance of migration. In addition to this, the results show that without any changes to the current culverts, on most velocities, 90% of the inanga population would not be able to overcome a 50-meter-long culvert.

The highest water velocity within a culvert that will still let 90% of the population pass is 0.16 m s-1 when the inanga itself swims at a speed of 0.2 m s-1 .