Well it could be a number of thinks that has made your fish disappear! Without knowing a bit of background about your stream I can only porvide you wit a list of possibilities:
The majority of NA's native fish migrate nd most fish migrate in March - it could be that they have started their journey.
The in-stream conditions may have changed to something that is not suitbable for the fish. For example:
1. The majority of NZ's native fish migrate and most fish migrate in March it could be that they have started their journey.
2. The in-stream conditions may have changed to something that is not suitable for the fish. For example:
- The water temperature has increased due to the stream bank shade being cleared.
- An increase in stream biota/algae (plants or that green slime, this process is called eutrophication. Plants require dissolved oxygen to grow, the bigger the plant the more dissolved oxygen needed. Fish also need dissolved oxygen to live and if they have to compete with the plants then may go somewhere else.
- The stream's water clarity may have changed most NZ native fish can tolerate living with a clarity measure of 40NTU but some more sensitive native fish can only survive in a clarity rating of 25NTU. The change in clarity could have come about due to sediment in the stream. Sediment could have been generated from earthworks (subdivision) or stock walking in the stream. This could have also been due to sediment runoff especially lately if you live where all the heavy rain has been happening. Sediment smothers macro-invertebrates (little insects) which fish eat.
- A reduction in water volume and flow due to someone taking water for irrigation or due to lack of rain.
- Runoff from a non point or point source pollution source, for example chemical runoff. 3. A downstream structure may have provided too much of a barrier for fish to get back up stream.
