Guest Post by Rex N. Gibson
Peter Trolove is the current President of the NZ Federation of Freshwater Anglers Inc. He commutes between his home at the North Rakaia huts and a batch at Okarito. Hunting and fishing are passions of his. Peter has degrees in both Veterinary Science and Aquiculture.
In his current role Peter has several environmental issues that he is currently tackling. He recently met with the Minister of Agriculture about the Federation’s concern over the diffuse pollution from intensive dairying to Canterbury’s lowland rivers, and in particular the dramatic decline of the endangered Stokell’s smelt from the Rakaia River hapua. These smelt are a key part of the diet of kahawai, trout, salmon and various native birds in the estuarine and immediate sea areas of Canterbury’s rivers.
The good news is that a Canterbury University Masters student is about to begin a study on their decline.
Another environmental issue has since been raised by Peter. In a further communication to the Minister he stated “This matter is more personal as it concerns a trout I caught in the lower Paringa River in 2014 that had its entire gut lining stained “1080 blue”. As a qualified fish vet and ex meat veterinarian I believe my observations and concerns merit further investigation &/or a precautionary response“. He awaits the response.
Peter had opened the fish and noted a fatty liver and a mass of fat where the stomach joins the intestine. Peter is clear that “This is evidence this trout had been feeding on  pellets for some time, probably washed down from the salmon farm upstream”. His specialist knowledge prompted him to immediately discard the fish (Private toxicology tests would have set him back $500).If a normal angler is fishing in a catchment where there has been a recent 1080 drop, he or she would be unaware of these symptoms.
This article is not about whether or not 1080 is an appropriate tool in controlling feral mammals designated as “pest species”; it is about the status of 1080 as a possible contaminant of trout flesh, our most significant (harvested) recreational fresh water fish. There is plenty of data about 1080 “facts” available on the internet. You make up your own mind.
The main research paper on the topic was a Cawthron Report No. 2011, titled “1080 uptake and elimination in rainbow trout” (30 October 2014).
Sadly this paper raised more concerns for anglers than it provided answers;
- 48 hours after treatment a trout dosed with 1080 (5mg) reached a maximum of 4.7 mg/kg in its fillet.
- None of the treated trout showed clinical signs. (So an angler would remain unaware a trout might contain 1080 toxin).
- The elimination study was unsuccessful in determining the half-life of 1080 in trout. 1080 levels remained high in the trout fillets even after the 5 days of the study period.
- A single pellet of 1080 contains 12 mg of the toxin. The study dose was just 5 mg.
- A trout may take in more than one pellet; after all a trout can hold up to 13 mice or 50+ snails in their gut!
- The numbers of trout used in the study were too small to have any scientific or statistical confidence in the study.
- The authors stated further studies were required to determine the rate of elimination of 1080 from rainbow trout. I am unaware of any such studies occurring.
MPI also published a paper “Evaluation of Fish and Game food chain exposure pathway for human consumption of trout from within a 1080 treatment area”. (2016). It was built on an assumption that trout were unlikely to ingest 1080 pellets. To this reader it appears to be primarily designed to dismiss the risk of 1080 entering the food chain in this manner. They produced the unacceptable response that “MPI is of the opinion that any food safety risks can be mitigated if anglers are advised to avoid consuming trout from waterways in a 1080 drop area within 7 days of the baiting operation”.
We must ask why just 7 days? Surely this is nothing better than a guess. Does this confirm that they know 1080 drops are definitely affecting trout? The paper also ignores the effect of trout size on 1080 ingestion, and even compares the likely physiological response of trout with mammalian studies. COME ON MPI!!! Comparisons of cold blooded and warm blooded animals are rarely valid.
The piece de resistance in all this is questioning of 1080 in waterways, is that there is a salmon farm upstream from where Peter caught his trout. It is highly likely that excess salmon food pellets get washed downstream. It is also highly likely that trout get an appetite for such pellets; just as they do in the Twizel canals.
These two photos show fish food pellets on the left and 1080 on the right. This year the size of the 1080 pellet has been halved bringing it more into the fish food pellet size range. Both pellets go slightly darker when wet. We have to ask ourselves, as anglers, if a trout, with a brain the size of our small finger nail and which has acquired a taste for fish food pellets, will spot the difference as pellets bob along in the river current?
I rest my case. 1080 (sodium monofluoroacetate) would certainly leave a sour taste in any angler’s mouth. It is a bit like serving up trout and asking your guest “Would you like 1080 with that”.
For further reading on the risks of using environmental poisons that we don’t know enough about, by a reputable scientist, try this URL, https://1080science.co.nz/aerial-1080-poisoning-in-new-zealand-reasons-for-concern/
Note that the New Zealand Federation of Freshwater Anglers exists to advocate on behalf of anglers. It is affiliated with fishing clubs across the country and has around 500 individual members. Membership is FREE. Go to their website to enroll: http://www.nzffa.co.nz/ or Facebook page https://www.facebook.com/NZFFA/.