When finding nothing is OK

The upstream end of the saltwater wedge is a great place to start searching for inanga spawning sites.

Diagram © EOS Ecology | www.eosecology.co.nz
Sourced from the National Inanga Spawning Education Programme, Part 2b: Experience – Inanga/Whitebait Find the saltwater edge. Available at https://shorturl.at/TzkuG

Uuugh. Fail. I am a bad ecologist.

I spent all this time traipsing around the field and found nothing, no sign of even one fish scoot, one egg or one eel ripple. Nada.

I worried that my client would be cross, I’d made an error in my plan, froze in wild South Wairarapa conditions, and it was all for nothing.

But was it?

I remembered one of the nerd golden rules – in science, a negative result is just as good as getting alllllll the results.

There is always a question we are asking when we embark on any research. In this case, where do īnanga (whitebait) spawn in the lower Wairarapa Moana area?  We knew some information, but there were still places unsurveyed and word on the street was that likely spawning habitat was there, babies and adults have been seen… but we needed hard evidence!

We prepared a field research method and plan based on our knowledge about how these fish breed. We needed to think about flooding, salinity, tides and habitat.

We went ahead and did the surveys, and well, there were no positive results. We found nothing. The fact īnanga wasn’t found or seen, nor any spawning activity or eggs, was weird! The habitat was there, but where were the fish?

Sometimes, you just don’t see expected outcomes or events.

And it’s OK! Dinna panic lass!

This is still really good information. It’s especially good to report this for several reasons.

We can report on what we did see, what we expected to see and what we didn’t see. So, for example, we did salinity testing and mapped where the saline water from the nearby lake was entering the freshwater channels – a key hotspot for īnanga spawning. We saw an excellent *potential* spawning habitat within this zone and plenty of opportunities to improve/enhance what was there. It was still good to note where spawning may happen. The water was only brackish (slightly salty) at best, and the bank gradient was nice and low in places but too steep in others (needing really high tides or inundation to allow fish to wriggle in amongst the grasses and reeds to spawn). The spawning habitat – bankside grasses and other plants – was patchy and recently disturbed.

So now we can ask more questions and pinpoint or zoom in on certain key areas. We can investigate again. These things can be a bit like a ‘needle in a haystack’ scenario, even though we were hopeful to see some action or the results of action (eggs). You just have to try again.

We recommended repeating the surveys at different times, using a different method, and surveying adult fish separately to see what the adult populations were looking like.

There are now more questions, like:

• Why aren’t the fish in here in big, obvious numbers?

• Have they been eaten, or is there no food for them?

• Did they get displaced by recent weather events (floods etc.)?

• Was it a very specific ‘right place, right time’ scenario that we missed?

• Is the hydrology too modified, and the adult fish aren’t getting the signals they need to be able to congregate?

• If that is the case, where do the fish go without a regular saline wedge (spawning zone)?

• Are they trapped upstream or downstream (are there barriers to their movement)?

• Did they get smothered by sediment in a flood?

From doing an initial survey that doesn’t uncover much hard evidence of spawning, we still learned a lot.

Bottom line – if this happens to you, don’t be disheartened! Write it up, find the next lot of questions and go in for round two!

The EOS diagram (at the top of this blog) is an example of an average-sized river and catchment. The diagram above shows an example of a larger, high-gradient river (big but fast-flowing). The saline wedge can move further inland because of the bigger river catchment. Depending on the size of the river or stream, the spawning zone can be as small as a couple of meters in length or up to kilometres in length. I surveyed one that was 3.6km long, but a colleague once did a survey and found the spawning area over 20km long (Whanganui awa).