Date: 04 February 2021
Below are links to monthly reports from the Waipa trap. These are presented as graphs and tables for each month, with the previous month and same month of last year included.
Each file includes the below data for brown and rainbow trout (male and female):
- average length
- maximum length
- average weight
- maxium weight
- condition factor.
Summary of the 2020 trap season
The start of the 2020 Waipa fish trap monitoring programme was delayed by a couple of weeks due to the impact of COVID-19. It got underway in mid-May and remained operational until the end of November.
Data shows that 1149 fish passed through the trap during the season, which equates to a 47% increase from 2019.
Early season numbers were relatively low. However, from June all biometric parameters show significant increases – particularly for rainbow trout. Both the average length and weight of trout processed this year was significantly higher than 2019.
The data confirms 2020 was a very good season in terms of numbers, biometric parameters, and conditions. This aligns with data collected from the escapement count programme, reinforcing the quality and scale of the 2020 spawning season.
Detailed analysis will apply adjustments, based on the number of fish recorded in the downstream pen of the trap that had avoided upstream monitoring – usually linked to flood events. The adjusted data will then be compared to the full dataset from the previous 20 years.
Reports from 2020 winter season
The data recorded from the fish trap in November continues to underline the quality of the 2020 spawning run. The Trout processed were bigger and in better condition than those encountered the same time last year. This has become a reoccurring theme which aligns with reports from anglers.
The figures are very similar to the previous month, with a reduction in overall numbers as we would expect (69 compared to 75). While reduced in numbers the Rainbow females were in even better condition.
Brown trout have finished spawning, so they are not present in the November data.
October data reveals a considerable drop in trout spawning numbers compared to the previous month (77 fish compared to 156). This is consistent with previous years and tells us the Rainbow Trout spawning season is tapering off. Brown Trout have largely completed spawning, so we only see a few occasional individuals appearing in the trap.
Condition factor remains very high, reinforcing the excellent condition of trout witnessed this year. While specific figures are slightly lower that last month, they are even better than those measured in October 2019.
The data continues to support reports from anglers, who tell us they are having an outstanding fishing season.
The excellent season continues with the number and condition of trout higher than recorded in September last year. The overall figures may be down compared to the previous month, but this aligns with expectations and simply indicates we are past the peak of the annual spawning run.
We also experienced three flood events, which will have allowed some fish to bypass the spawning trap. Fishery scientists will have a clearer idea of how many migrating trout were missed when monitoring is complete on the downstream pen of the trap – fish that were missed will not have been fin clipped.
Brown trout have largely completed their spawning activities and those encountered in the trap could well have already spawned below the trap and are now seeking food further upstream.
The ongoing improvement in the Rainbow trout data (compared to previous years) further supports the experiences of anglers, who report they are having an outstanding fishing season.
Positive trends continue with the number of trout processed this month eclipsing those encountered during the same period last year – we processed 241 trout compared to 107 last year.
Average lengths are tracking similar to last month but again exceed last year’s figures. The same is true for weight and Condition Factor (CF). Almost all average weights and CF figures were the same or higher this year compared to 2019. The only exception is Brown Males (BM), which may not have been as large as this year but were in outstanding condition in 2019.
The number of trout recorded this month is nearly double the number measured in July 2019 (298 trout compared to 177). Numbers are also slightly up on last month, despite the relatively low rainfall experienced in July.
Rainbow trout continue to be heavier than previous years with males doing particularly well. Their high Condition Factor (CF) is also better than previous years - exceeding the excellent CF recorded last year.
The data gathered this month reveals trout were present in both greater numbers and increased sizes, when compared to the previous month. Average lengths and weights are greater for both species and sex - brown and rainbow trout, male and female. The same is true for maximum size and weight.
Rainbow trout are heavier than we’ve seen for several years at the Waipa spawning trap, with females averaging 2 kg and males 1.7 kg. This aligns with reports from anglers and the wider fishing community.
The largest fish recorded this month was an excellent brown jack that measured 710 cm and weighed 4.7 kg.
Due to COVID-19 restrictions the spawning trap was not reinstated until the middle of the month which significantly reduced opportunities for data collection.
Therefore, it is no surprise to see fish numbers down on the previous year as this has reduced our sample size.
Lengths and weights are within the expected range, with a visible improvement in the Condition Factor (CF) for Rainbow males (RM).
Limited sampling opportunities combined with low headwater rainfall this year (80 mm May 2020, compared to 230 mm May 2019) may have impacted the results.
Looking ahead, it will be interesting to see how the excellent fishing experienced by anglers in the lower river translates into data collected from this headwater location.