Fishing News index>Salmon Report 2007

2006/07 Salmon Management Report for the North Canterbury Region

Abstract
Anglers’ hopes of an improved salmon run last season were satisfied with reports of good numbers of salmon observed in most of the east coast salmon rivers at different times throughout the season. However, catching them proved to be another story. Angler catch records for the 2006-2007 also confirm this and show anglers had limited success in both the Rakaia and Waimakariri Rivers. Although catches were higher than the previous season in both rivers, they were the lowest on record as a percentage of the total run in the Waimakariri and a similarly low catch rate was seen in the Rakaia. Spawning numbers in the headwaters were up almost five fold on the previous year in the Waimakariri and more than double in the Rakaia compared to the previous season.

Introduction
Both North Canterbury and Central South Island Fish & Game Councils have been monitoring salmon returns for fifteen years. The salmon monitoring program is continuing to add knowledge of the salmon fishery for scientists and fishery managers. However, with the many environmental variables involved in salmon survival, the ability to predict future returns is still some way off.

Methods
Estimates of annual salmon returns consist of combining the number of salmon that reach their spawning streams (spawning escapement), angler catch, and returns to hatchery facilities such as Silverstream and the Fish & Game managed Montrose Salmon Farm.

a) Spawning Escapement
The main spawning streams in both the Rakaia and the Waimakariri River catchments were assessed using a program of repeated live fish surveys conducted from a helicopter. The results from these counts were fed into a model developed by NIWA and estimates of the total number of spawning salmon were obtained. The model works by plotting live fish counts on a curve. The area under that curve represents the total fish days for that spawning stream. An estimate of the number of fish that reached the spawning streams is then obtained by dividing the total fish days by an estimate of the average residency time of an individual salmon in the spawning stream.

The Waiau and Hurunui aerial program has been reduced to a single aerial trend count on each of these rivers during the peak of the spawning period. A single trend count provides a sufficient level of understanding of the changes in annual spawning success in these rivers at a greatly reduced cost.

There is less precision in the estimate generated by the modelling program in years with below average returns for these two rivers. This is because there is significant annual variation between the different spawning areas, with some traditional areas not used at all, while the most preferable sites are almost fully utilized in low return years. Another factor that complicates annual comparison of the Hurunui and Waiau Rivers is that some of the traditional spawning areas are in the main stem and are subject to a higher risk of spawning failure due to flooding, therefore creating greater annual variation.

b) Salmon Residency Research
Estimates of spawning escapement from the NIWA model rely on the use of a variable known as the ‘salmon residency time’ (SRT). This is the assumed time each salmon spends in the spawning stream where it is likely to be seen during the aerial survey. The model estimates ‘salmon days’, that is the number of days spent by salmon in the spawning stream. For example if 1000 salmon each spent ten days (SRT) in the Hydra Waters then there would be 10,000 salmon days. In order to calculate the actual spawning run salmon days need to be divided by the SRT. 

Before Fish & Game began salmon residency research, the only spawning stream with a known SRT figure was the Glenariffe Stream where an estimate of ten days was derived by MAF during the 1970’s. In 1998 Fish & Game commenced a long-term research program with the intention of gaining individual SRT estimates for all significant spawning waters in the region. No salmon residency research was undertaken in North Canterbury salmon spawning streams last season.
 
Example of the Area under the Curve Graph (Poulter River 2006/07)

 
c) Angler Salmon Catch
A phone survey was carried out on 1,200 randomly selected licence holders in the region (adult whole season, principal family member and complimentary, to ascertain the number of salmon that were caught from each river. 640 of these anglers were successfully contacted and willing to participate in the survey. All of those anglers had no trouble recalling exactly how many salmon they had caught last season. The survey results were then analyzed and the results extrapolated to include all licence holders in the above categories. An estimate of the total salmon catch in each river was then calculated. A similar survey conducted in the Central South Island region provided data on the number of salmon caught by their anglers in North Canterbury Rivers.

The angler phone survey is designed to provide the North Canterbury Fish & Game Council with an estimate of angler salmon harvest with a high level of precision from our most popular rivers, the Rakaia and Waimakariri. The significantly increased sampling effort that would be required to obtain such precise estimates from our less popular rivers, namely the Hurunui and Waiau, is not considered justified.

Unfortunately, this means that estimates for these rivers are less precise and can be highly influenced by the harvest data of only one or two anglers. For example, only one angler was contacted in the survey that had caught a salmon from the Waiau River, resulting in an estimated harvest of only 18 salmon caught by anglers in the Waiau River all season, whereas if that same angler had caught two salmon the estimate would have increased to 36.

Results
a) Rakaia River
The total run in the Rakaia was almost double the 2005/06 season with almost 4,000 salmon returning to the river to spawn. Angler catch remained similar to the previous season but spawning escapement was the highest seen in eight years at almost 3,000 fish. The total catch was not boosted significantly by the Montrose hatchery returns which made up only 7% of the total run (180 fish). The Hydra Waters was the standout spawning stream last season with almost 1,500 salmon returning to spawn, the highest seen in eight years. Mellish Stream, a tributary of Lake Heron which flows into the Rakaia River a few kilometres above the Glenariffe had similar number of salmon return as the Hydra Waters the previous season but this season only saw around 30 salmon return.

 
b) Waimakariri River
Waimakariri returns were more than double the previous seasons with angler catch remaining similar to the previous seasons at 1,373 and spawning escapement almost four times greater at 2,659. The standout tributaries in the Waimakariri River were Cora Lynn and Cass Hill Streams which both saw more salmon returning this season than the Poulter River. Cora Lynn had its highest returns ever with almost 800 salmon, which was one and a half times more than returned to the Poulter River. Returns to the Silverstream hatchery were relatively poor with only 275 salmon returning to the trap.

 
c) Angler Catch
A phone survey was carried out on 1,200 randomly selected licence holders in the region (adult whole season, principal family member and complimentary), to ascertain the number of salmon that were caught by North Canterbury anglers from each of the salmon rivers. Six hundred forty (640) of these anglers were successfully contacted and willing to participate in the survey. All of those anglers had no trouble recalling exactly how many salmon they had caught last season. The survey results were then analyzed and the results extrapolated to include all licence holders in the above categories. An estimate of the total salmon catch in each river was then calculated. A similar survey conducted in the Central South Island region provided data on the number of salmon caught by their anglers in North Canterbury Rivers.

Both the Rakaia and Waimakariri Rivers had significant decreases in the percent of the returning salmon that were caught by anglers although the actual number of salmon caught in each river was higher than the previous season. The angler catch in the Rakaia River was 1110 salmon, or 28% of the total run and the Waimakariri River had an angler catch of 1373 fish, or 34% of the total run.

 d) Natural Spawning (hatchery returns excluded)
The main spawning streams in both the Rakaia and Rangitata Rivers had above average spawning returns last season.
 

e) Hurunui / Waiau River Salmon Runs
The total run is not calculated for the Hurunui or Waiau Rivers as the area under the curve model cannot be used when only one aerial count in conducted. The aerial trend count conducted on the 8th May recorded more than double the salmon numbers than seen the previous season in both the Hurunui and Waiau Rivers.

Unfortunately due to the relatively low number of anglers who successfully fished these rivers who were contacted during the phone survey, there is a large degree of error associated with these calculations but the figures show similar low catch rates to the larger rivers further south. Whilst the estimate of angler catch varies from year to year, actual angler harvest and spawning numbers have followed trends similar to the Waimakariri and Rakaia Rivers most years. Other than the number of salmon returning to a river, angler catch is affected by the number of days the rivers are fishable, the frequency and duration of floods and all the main salmon rivers on the east coast tend to mirror each other in these aspects.

f) Rangitata / Waitaki River Salmon Runs
Salmon returns for the Central South Island salmon rivers showed the Rangitata had a reasonably good season but the Waitaki River showed very similar characteristics to the North Canterbury Rivers with very poor angler catch rates but reasonable spawning numbers. North Canterbury anglers caught an estimated 514 salmon in the Rangitata River which is up significantly compared to catches over recent years.

g) Out of Region Anglers
Angler catch records from Central South Island Fish & Game phone surveys show 207 salmon were caught in the Rakaia River, 19 in the Waimakariri River and 3 in the Waiau River by Central South Island anglers. Previous phone surveys indicate that very few salmon are caught in all but the Rakaia River by Central South Island anglers and this is also true of this year’s surveys. 

Discussion
 A few of the spawning streams stood out from the others this season. In the Rakaia River, The Hydra Waters had its best run in eight years with almost 1,500 salmon returning to spawn. Glenariffe Stream also had its best return in eight years with almost 600 spawning salmon. In the Waimakariri River, Cass Hill Stream had its best return in nine years with over 500 spawning salmon and Cora Lynn Stream had its best spawning numbers since aerial counts began fifteen years ago with over 500 salmon returning.

The salmon enhancement program has continued in the North Canterbury region with strong volunteer support for the Fish & Game hatchery at Montrose and enhancement of secondary spawning streams. This program has been in progress for six years now and includes smolt releases, eyed ova planting, transfer of fry and smolt donated by hatcheries to spawning streams and an increase in Fish & Game funded releases from the Silverstream hatchery. The current salmon enhancement program is as much an education tool as it is insurance against low spawning survival rates.

Returns to the Rakaia River last season from the release of 60,000 fin clipped salmon smolt from Montrose in August 2005 were surprisingly low. Only 180 salmon returned to the Montrose hatchery. Relatively small numbers were also caught by Rakaia anglers, however anglers fishing on the south side of the Rangitata Mouth reported catching good numbers of these fin-clipped salmon earlier in the season. The Rakaia Salmon Fishing Competition reported around 22% of the salmon weighed in were fin-clipped Montrose fish.

Many anglers would not have noticed whether the salmon they caught was fin-clipped or not, therefore specific questioning about fin-clipped salmon in the angler survey is of no use to calculate total angler catch of these hatchery fish. However, it can be estimated from angler catch statistics for the Rakaia River that anglers caught 28% of the Montrose salmon returning to the Rakaia River. Add this to the hatchery return and this brings the total return of Montrose salmon to around 0.42 % (250) of the initial 60,000 released.

Returns to the Silverstream hatchery were also relatively low last season, accounting for approximately 10% of the Waimakariri salmon run. The annual variation in returns to this hatchery is however likely to be at least partially due to the annual variation in numbers of salmon released from this hatchery.

Both North Canterbury and Central South Island Fish & Game Councils have been intensively monitoring salmon returns for 15 years now. The salmon monitoring program is continuing to add knowledge of the salmon fishery for scientists and fishery managers. However, with the many environmental factors involved in salmon survival, understanding the fishery is still rather a rather complex goal.

Studies carried out in North American salmon rivers suggest that it the period shortly after salmon fry and smolt enter the marine environment that heavily influences the year-to-year variations in salmon survival and this is thought to be largely determined by climatic and environmental variations. In some years the ocean environment greets migrating salmon with an abundant food supply and relatively light predation pressures, while in other years food is scarce and predation pressures are high.

Each season it appears that angler confidence in the salmon fishery varies depending on angler catch rates. Thinking optimistically, the record low spawning numbers of the 2000-2001 season did not have a significant negative effect on the number of salmon returning during the 2003-2004 season as some anglers feared and recent spawning numbers are hopefully capable of producing a bumper run in coming years.

Fish & Game are constantly seeking a better understanding of the salmon fishery and predicting salmon runs based on past returns and forming management decisions around these predictions are still beyond our abilities. There is however very little salmon research being undertaken in New Zealand at present and given the current state of the fishery it would be wise to continue to expand our knowledge of the salmon run. Staff believe that salmon spawning numbers have improved significantly and that it would be appropriate to install a residency research trap on one of the primary spawning streams that has not been trapped yet.
 
Acknowledgments
I would like to thank the following for their assistance with the 2006-2007 salmon program.

1. Jim Stephenson (St James Station), David & Rosemary Gunn (Lake Taylor Station), Ted & Sandy Phipps (The Lakes Station), John Westenra (Craigiburn Station), Mark Fraundorfer/Richard Hill (Flock Hill Station), Alister, Pru & Mark Ensor (Glenariffe Station), Don & Julie Paterson (Manuka Point Station), James & Jane Smiley (Mt Algidus Station), Hamish & Belinda Ensor (Glenaan Station), Tim & Anna Hutchinson (Double Hill Station), Charlie, Duncan & Fiona Ensor (Glenrock Station), Christchurch Helicopters, New Zealand King Salmon and their Tentburn Hatchery Staff, Ad & Marjo Bruijn (Montrose Station), and all the staff at NIWA who provided assistance at various times.

Steve Terry
Fish & Game Officer
3 August 2007

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