FISHERY MANAGEMENT Taking stock of stocking The Piscatorial Society’s Bob Wellard questions the wisdom of stocking yearlings into wild fi sheries and looks at the success of their ‘naturalisation’.

he Piscatorial Society is early spring and summer. One-year-old trout, techniques and improvements to habitats one of the oldest angling often referred to as ‘yearlings’, of 6-8" (150 – for all life-stages, began to raise questions 200mm) were, until recently, stocked in July about the need for continued stocking of societies in England, if not each year. yearlings and feeding them in the river. By the world. Founded in 1836 Historically it was perceived that a large 2007, the practice of feeding fi sh in-river had theT Society began as a group of friends proportion of stocked yearlings quickly become ever more popular and the impacts who gathered together to dine and became ‘naturalised’ in the wild and that of large-scale feeding, not surprisingly, discuss fi sh and fi shing. It was heavily they made a signifi cant contribution to the had begun to raise a few eyebrows, with available trout resource for angling. A review questions being asked of the Environment involved in early freshwater fi shery of past journals would confi rm this to have Agency as to its legality and appropriateness, legislation along with bodies such been the case...“The success of the Society’s especially in rivers with SSSI (Sites of Special as the Thames Angling Preservation river management policies has resulted in Scientifi c Interest) and SAC (Special Areas Society. By the 1860s it had become many of its waters holding a good head of of Conservation) designations. The negative wild and ‘naturalised’ fi sh. These fi sh react ecological impacts of adding nutrients a conventional fi shing club providing in a more natural way than stocked fi sh, and organic matter to the river system, fi shing for its members, and it still which frequently have diffi culty in adjusting accumulated with other point source and fl ourishes today. Although members to a river environment and have shorter diffuse nutrients, was no doubt impacting originally fi shed for all sorts of fi sh survival rates.” on the river ecology, including wild salmonid (the Society’s crest still represents Armed with this post-war evidence, the production and the potential for increased Society continued to stock several sites, exposure to predators caused by seasonal the head of a pike), the Society now but subject to the keepers feeding the concentrations of fi sh and the so called concentrates on fi shing for brown stocked fi sh in the river, thereby providing ‘feeding station syndrome’. trout and grayling on its chalk ‘improved’ fi shing in the years that followed. In 2008, in responding to these questions, streams in Hampshire and Wiltshire, Improvements in catches, most likely due the Environment Agency and Natural to a fl ourishing wild trout population and England clarifi ed their position on in-river including the Wylye, the Test, the the result of better informed management supplementary feeding of trout in the Itchen and the Hampshire Avon with upstream dry fl y or unweighted Figure 1. Yearlings present nymph imitations dressed lightly in 3 months after stocking the style of G.E.M. Skues. The Society is more than just a Site No 2008 2009 2010 2011 fi shing club. It has at its core three key 1 2 4 5 3 2 5 8 16 2 objectives. First, to maintain a fellowship 3 1 2 1 5 of fl yfi shers and the tradition of fl yfi shing, 4 2 3 1 0 where possible, for wild or ‘naturalised’ 5 1 3 0 2 6 0 2 1 3 brown trout and grayling. Secondly, to Mean 1.8 3.7 4.0 2.5 preserve what remains of the chalk stream environment; unpolluted water, healthy and appropriate weed growth and good fl y Figure 2. Yearlings present hatches. Thirdly, to enhance the Society’s 15 months after stocking libraries and archives. Whilst the Society continues to operate a number of its waters as wild catch-and-release Site No 2009 2010 2011 fi sheries with no stocking, supplementary 1 0 0 0 stocking is carried out in some waters “to meet 2 0 0 0 the needs of those anglers who might wish to 3 1 0 0 4 0 0 0 take a fi sh home”. Where stocking is carried 5 1 0 0 out, it is done on a little-and-often basis with 6 1 1 0 ‘takeable’ 1-2lb triploid brown trout being Mean 0.50 0.17 0.00 introduced to selected sites throughout the www.wildtrout.org 65 Salmo Trutta FISHERY MANAGEMENT

already beginning to fade. In 2010 we moved somewhat handicapped by the fact that it to using VIE (Visible Implant Elastomer) seems completely oblivious to predators and tags. The VIE tags, a rather more expensive doesn’t understand the concept of ‘taking method but quick and easy to insert with no cover’ when predators are active. From ill effect and widely used for batch marking, my own observations the stocked yearling had good retention rates (Summers, et al feeds, or should I say tries to feed, much 2005) and were inserted under the skin on as it did in a hatchery, at any time of the the belly of the fi sh with a different colour day and then seemingly with a low energy used for each year. intake at a high metabolic cost. Again this Stocking sites were assessed for their behaviour has been well documented by suitability in providing a best-case scenario others: “Hatchery brown trout, introduced for juvenile salmonid survival: medium-high for experimental purposes, fed less, moved gradient channels with plenty of in-river more, and used cost-minimising features weed cover (Ranunculus spp.), marginal of the substrate less than wild trout. It is Damage caused by plants in abundance and a plentiful food postulated that high-energy cost is a major piscivorous bird supply (Riverfl y AMI scores). Our stocking cause of mortalilty among hatchery-reared was only in small densities and with the brown trout stocked in streams, that at best quality fi sh available. Each reach was high population densities foraging sites stocked with 50 yearlings, with no feeding are limiting factors, and that growth rate taking place for the duration of the study. and drift of feeding salmonids is density Weed and water levels were managed by dependant” (Bachman 1984). the Society’s keepers along with the normal Even our limited study has revealed licensed control of piscivorous birds, as in suffi cient evidence to suggest the previous years. naturalisation of stocked trout yearlings without in-river feeding is highly questionable Results and provides a very poor return. The specifi c Quantitative electric-fi shing surveys (three- cause of such signifi cant losses being most run, catch depletion methodology, with stop likely due to a number of factors ranging nets at each end) were carried out in October, from an increase in intra-specifi c and inter- three months after stocking, and thereafter specifi c competition leading to starvation at 12-month intervals. The results, shown in and/or migration, high levels of predation Figures 1 and 2, reveal zero to 32% of a total and/or physical damage and disease or a of 50 stocked yearlings remained at each combination of all of these. Secondary infection of bird site after 3 months (July to October) in each All things considered, it is also possible wounds year surveyed. Zero to 0.5% remained after the naturalisation of larger, takeable-size 15 months. No yearlings were present at any stocked fi sh is questionable and that is maybe of the survey sites after 27 and/or 39 months something we will look at in more detail in Wessex and Hampshire areas including of sampling. Of a total of 1200 yearlings future. In the meantime, we will continue to the Hampshire Avon, the River Test and stocked, only 72 were still present after three evaluate our stocking policies and strive to River Itchen with the following statement: months (6%) and just two were still present identify and improve upon any restrictions “Unless consent is granted, in-river feeding after 15 months (0.16%). that may be limiting natural production of is an offence under Section 85 of the Water Of those yearlings captured, a large wild trout in all our waters. Where we do Resources Act 1991. This activity would proportion was observed to be in a poor feel there is a need to stock, we will no longer currently not be granted consent by the condition and was of a lower weight when stock with yearlings but introduce only non- Environment Agency. This position is compared to wild fi sh of a similar length. breeding trout (all-female triploids) of an supported by Natural England.” Several yearlings exhibited predator appropriate size (1-2lb). In 2008, in order to ensure we at least (possibly cormorant or heron) damage and/ And so it is, with a friendly nod to the had some science-based evidence for future or secondary infection past, the Society continues to maintain a decision making, the Society undertook to fellowship of fl y fi shers and the tradition of review the yearling naturalisation process Conclusions fl yfi shing, where possible, for wild brown and assess the potential for yearling survival As we are all too aware, cormorant activity trout and grayling. and/or displacement, without feeding, over a has increased signifi cantly in recent years and 3-year period (July 2008 - Oct 2011). evidence from several sources would suggest References: Our study began in 2008 with 300 that stocked trout are far more vulnerable to Bachman, R. A. 1984. Foraging behaviour of free- hatchery-reared (triploid) yearlings being predation than wild trout. ranging wild and hatchery brown trout in a stream. tattooed for identifi cation, using Pan-Jet But then this should not really come as Transactions of the American Fisheries Society 113: dye marks to the pectoral fi ns (2008 - left a surprise, especially when one observes 1-32. pectoral /2009 - right pectoral). Whilst this these stocked fi sh in the wild. A stocked Summers, D.W, Roberts, D.E, Giles, N, and Stubbing, D.N. 2005. Retention of visible implant and visible appeared to work well, during the second fi sh, a product of domestication through implant Elastomer tags in brown trout in an English survey (2009) we noticed dye marks from generations of line-selected breeding chalk stream. Journal of Fish Biology (2006) 68, yearlings marked the previous year were and grown in a hatchery environment, is 622–627.

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