Report on the 2006/07 Angler Diary Scheme
Dear Angler

The angler diary scheme has been running now for three fishing seasons and the support that you have given this programme is greatly appreciated. The following report summarises information gathered from the 2006/07 season and takes a look at the Waitaki anglers experience with didymo so far.

Information gathered from diarists covers rivers and lakes fished, catch and catch rates for both salmon and trout. Other data collected covers a wide range of information that includes various environmental conditions, specific reach or area information and anglers overall experience. This gives us the opportunity to see possible effects on catch rates and changes in angler perceptions. That information may not be presented here but we will be happy to present any analysis you wish, just let us know.

We provided diaries to 142 anglers in early October 2006. Of these diaries 104 were returned with 100 of them completed, the other four diaries were either incomplete or came with an apology. The 100 diarists who recorded daily fishing activities visited 81 rivers and lakes and landed 325 salmon and 1,190 trout for 2,030 days fished at an average of 4.07hrs/day.

Rivers supporting sea-run salmon fisheries, such as the Rangitata, Opihi and Waitaki were visited by 64 anglers who targeted salmon. These anglers landed 287 salmon in 3,648 hours with a success rate of 1 salmon on average every 12.7 hours. The average weight of these salmon was 6.65kg.

Five anglers targeted salmon in land-locked fisheries such as lakes Coleridge, Heron and Benmore. These anglers caught 23 salmon at a catch rate of 2.9 hours per fish and 20 trout at 3.4 hours per fish.

Seventy three trout fisheries were visited on 103 days by 64 anglers.  These anglers accounted for 1,076 trout at a catch rate of 2 hours per fish. Brown trout comprised 63% of the catch. In addition to trout anglers also caught 18 perch and 6 land-locked salmon. Three trout anglers got lucky and landed 6 sea-run salmon averaging 7.2kg.

The following table provides information on angler effort and catch for rivers or lakes visited by more than 1 angler. Anglers fished for T = trout, S = salmon, T/S = trout and salmon.

In addition to these fisheries diarist recorded solitary trips to a further 49 rivers and lakes from the Pelorus in the north to the Aparima in the south.

Diarists who recorded fishing trips to the Waitaki have given us an opportunity to take a look at angling with didymo and the following information describes their experiences so far.
 
Didymo first appeared in the lower Waitaki near the end of January 2006 and in the following 12 months had spread from Kurow to the sea, a distance of 60km. Didymo had minimal impact on diarists who fished the Waitaki until the 2006/07 fishing season. It was during this season that comments regarding the negative impacts of didymo became more frequent. Early season trips to the Waitaki resulted in some frustrating conditions for anglers with didymo fouling lines and gear 90% of the time. Diarists also came across the invasive algae in the stomach contents of trout (mainly rainbows), some tightly packed. Despite this there were times later in the season when the angling experience was less affected by didymo. Anglers found that visits later in the season resulted in 1 out of 10 casts being affected by the algae. So what happened to the didymo? The Waitaki River experienced high flows for prolonged periods this summer and during this time didymo was the cause of much angler frustration. Flows were then reduced by about half and the impact of didymo on anglers was greatly reduced. This reduction in didymo’s adverse effects may be due to changes in flow which could have affected didymo’s growth by altering its preferred habitat. Flow velocities that are too great in midstream don’t allow didymo to grow so it tends to grow at the edge of braids and therefore when the flow is reduced these areas become dry.

Trout condition in the Waitaki if anything showed a slight improvement (Fig 1) over the past three years and even rainbows with stomachs packed full of didymo were still in good condition from the angler’s viewpoint. This is interesting as didymo changes diet composition from large to smaller invertebrates and no change in condition suggests that Waitaki trout can sustain themselves on these smaller food items. Catch rates for Waitaki trout anglers were very similar over the past three seasons (Fig 2). This shows that on average trout anglers are still as successful at catching fish whether didymo is present or not.

Salmon anglers experienced similar conditions with periods where didymo was a major problem and at other times it was hardly noticeable. Salmon anglers were still able to catch salmon at a good rate this year (15.2 hours/fish). A small group of salmon anglers found didymo to be a problem, with clumps locking up guide eyes making retrieving difficult and covering their lures or spinners.

Overall our trout diarists found that the Waitaki River was fishing just as well last season, if not better than the previous two seasons. Trout condition was better and the catch rate was about the same. Even though didymo may affect diarists, they found that at times angling has changed little from pre didymo days. Salmon anglers are still catching fish when they are present and only a few are finding didymo a major problem. Waitaki diarists have shown that fishing with didymo is not as bad as some first thought and at times great fishing can still be experienced.

The graphs attached to this report are an overall summary of the major rivers and lakes fished by diarists for the past three seasons. The information covers catch rate (fish/hour) and their average fish weights. Please note that seasons marked with * are calculated from sample sizes less than 10 fish and therefore may not be accurate.

Diarists fishing for salmon over the past three seasons have experienced differing catch rates in Canterbury’s sea-run salmon fisheries (Fig 3). The Rangitata and Waitaki Rivers had a poor 2005/06 season with the other two seasons producing better returns. The Opihi did not follow this trend with a high catch rate in both the 2004/05 and 2005/06 seasons with the 2006/07 season showing a much poorer return for angler effort. The Rakaia River however had a more consistent catch rate for the past three seasons with the 2005/06 season not suffering a big drop like the other rivers in the region. Average salmon weights over the three seasons in the Rangitata River were relatively steady and a slight improvement was seen in the Waitaki and Rakaia Rivers (Fig 4).

In terms of catch rate the Waitaki and Opihi River fisheries were the best performers over the past three seasons, trout were caught at around 0.5 fish/hour or better in these rivers (Fig 5). The Rakaia and Rangitata Rivers produced some good fish with average weights for the three seasons of around 2kgs (Fig 6). Sea- run trout dominated in the Ashburton River accounting for the exceptional average weight of 2.89kg in the 2006/07 season.

Lakes Benmore and Aviemore had good catch rates for trout over the past three seasons (Fig 7). Lakes Heron, Opuha and Clearwater have showed a noticeable improvement in their catch rates for the 2006/07 season which is promising for these fisheries. Average fish weights for the region showed Lake Alexandrina had the best fish, averaging around the 2kg mark (Fig 8). Fish from Lake Benmore had a consistently good average weight above 1.1kgs for the past three seasons and it will be interesting to see if sockeye salmons presence in the lake increases this value. Sample sizes from the other lakes were unfortunately too small to get a reliable average. 

When the diary scheme was first introduced in the 04/05 season it was to run for three seasons, finishing with the 06/07 season. It’s time as a general angler diary scheme has now run but we see an important need to continue for a time with a Waitaki River diary to record what may happen as we come to terms with Didymo. Already last season we have seen some anglers recording very good results for the river and many comments of surprise referring to good fish condition. Long may that continue.
Please don’t feel we are casting you adrift. We will send diaries for the 07/08 season so you can continue your good habits but in terms of providing a summary of all diaries and trends in fisheries that may be beyond us now, we will however be concentrating on continuing with the Waitaki River fishery and please feel free to call if there is anything we can help with.
 
Thank you again for those who have contributed to the diary scheme and may your 2007/08 season be one to remember.

Yours sincerely

Hamish and Mark (Fish and Game Officers)

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