Measures for the conservation of pike: consultation

5. Proposals

5.1 There is a body of scientific evidence in support of the concept of protecting large fish (females particularly) within populations. Such fish provide a large number of eggs per individual and furthermore the eggs are often relatively large and hence likely yield particularly robust offspring. A stock of long-lived fish also provides buffering against a series of poor years for survival of eggs and juveniles enabling stock recovery. Hence, if managing a fish stock for exploitation it would be a sensible strategy to protect large spawners.

5.2 As well as providing population resilience, large size in pike is favoured by recreational anglers who generally value a fishery in terms of likelihood of catching a "trophy" fish rather than a large catch of small fish. Hence, it is a sensible strategy to protect large pike in recreational fisheries.

5.3 A theoretically possible negative factor would be cannibalism of smaller pike by these large fish. However, although this phenomenon has been recorded in some specific situations, there is scepticism that it occurs generally because size classes of pike favour distinctly different habitat types and hence for the most part are spatially segregated.

5.4 Large pike may be protected by imposing a limit on the maximum size of fish that may be removed. It has been shown that pike can be quite resilient to catch-and-release angling, with about a 5% mortality due to damage from hooking, but some variation between capture methods and studies (Arlinghaus et al., 2008). It is possible, however, based on results of studies on other species, that the level of loss from capture may be greater at relatively high temperatures.

5.5 Pike soon learn to avoid lures but not natural baits, and therefore some individuals may be captured on numerous occasions. The cumulative mortality risk is hence a consideration, particularly in waters with high fishing pressure and/or low abundance of natural food items.

5.6 Information on effects of catch size limits is available for a theoretical study (Arlinghaus et al., 2010) and an extraordinary N American study (Pierce, 2010) including surveys of 69 lakes, data for 9-17years of experimentation and up to 37 years of monitoring. This study showed generally large increases in the occurrence of large pike following implementation of maximum size limits of predominantly 70cm (with two sites using maxima as low as 51cm). There was no detectable effect on overall production, suggesting no strong regulation through cannibalism by large pike. Tiainen et al. (2017) similarly found a positive effect of maximum size limits (65cm) on abundance of large pike in a small sample of Finnish lakes. In general the empirical studies correspond well with the theoretical modelled predictions. Although based on few data, the Finnish study provides field evidence for the prediction that a maximum harvest size need to be supported by regulation of angling pressure if the rate of growth is insufficient to allow more pike to reach large sizes than are removed by incidental angling mortality.

Arlinghaus, R., Klefoth, T., Kobler, A., Cooke, S.J., (2008). Size-selectivity, capture efficiency, injury, handling time and determinants of initial hooking mortality of angled northern pike (Esox lucius L.): the influence of bait type and size. North American Journal of Fisheries Management 28, 123–134.

Arlinghaus, R., Matsumura, S., & Dieckmann, U. (2010). The conservation and fishery benefits of protecting large pike (Esox lucius L.) by harvest regulations in recreational fishing. Biological Conservation, 143(6), 1444-1459.

Pierce, R. B. (2010). Long-term evaluations of length limit regulations for northern pike in Minnesota. North American Journal of Fisheries Management, 30(2), 412-432.

Tiainen, J. M., Olin, M. J., Lehtonen, H. V. T., Nyberg, K. B., & Ruuhijärvi, J. (2017). The capability of harvestable slot-length limit regulation in conserving large and old northern pike (Esox lucius). Boreal Environment Research.

5.7 There is strong scientific support for setting a maximum harvest size but insufficient information to specify the precise limit.

5.8 We propose that any pike of more than 60 cm in length must be released.

5.9 The value of a bag limit depends on the productive capacity of a water for pike and angling pressure. Furthermore, if there is strong density dependence, then it may be advantageous to remove small pike, up to a point, to stimulate increased growth in those remaining. We acknowledge, however, that there is little information available on the density dependence of pike stocks in any Scottish fisheries and therefore propose that a precautionary approach - a one fish bag limit - is appropriate.

5.10 We propose that a general bag limit of one pike, of maximum 60 cm in length, per person per day to prevent the depletion of stocks by excessive removals or commercial exploitation.

5.11 Although no systematic research has been possible, there is a large body of anecdotal evidence indicating that taking pike for the table in substantial numbers has become increasingly common across Scotland in the last fifteen years or so. Sport anglers' catches – especially of larger fish - from many formerly productive waters across the country are widely reported to have fallen significantly. In the worst instances illegal methods are being used, but more common are the reports of groups of anglers fishing intensively for the table and taking all the pike they can catch either for personal consumption or sale.

5.12 We propose that no person can sell, offer or expose for sale any pike that has been taken by rod and line.

Question 1 – Do you agree that any pike of more than 60 cm in length must be released? Please add any evidence you have in support of your position.

Question 2 – Do you agree that there should be a general bag limit of one pike, of maximum 60 cm in length, per person per day? Please add any evidence you have in support of your position.

Question 3 – Do you agree that no person should be able to sell, offer or expose for sale any pike that has been taken by rod and line? Please add any evidence you have in support of your position.