Print Shortlink

Tweed BioBlog: Conservation Limits

Monday 26th – Friday 30th October 2015:

Monday – On leave: Tuesday – a meeting with MSS at the Faskally laboratory along with my counterparts from the Spey and Dee and the Lochaber and Galloway Trusts to discuss the new Conservation Limits (CLs) approach to salmon management. The aim was to prepare the way for a meeting of biologists from all the rivers and Trusts to discuss this sometime in early December. This new proposal replaces the absurd Kill Licence system that was proposed in the Wild Fisheries Review, as  biologically ignorant a concept as I have ever come across in a lifetime in salmon management (not to mention impossible in practice).  The proposed CLs system is similar to that already operating in other countries and is, in essence, very clear and very simple (and very sensible): ensuring that enough eggs are coming in to a river to stock it for the next generation. The Devil, as always, is in the detail, or in this case the data: e.g. the fecundity of Salmon varies from river to river, so local data is required if good estimates of incoming eggs are to be made, but without river netting stations and with so much Catch & Release, this is now difficult to get in many places. Here on the Tweed, James has been collecting eggs from smokeries for some years now and so we do have a local Fish Size – Egg Number relationship which has already improved the spawning target estimates for the areas upstream of the fish counters so instead of just having numbers of fish passing upstream, we can estimate the numbers of eggs going up through a counter. Similarly, the numbers of eggs needed varies from catchment to catchment: a productive system like the Tweed with lots of gravel and rich feeding needs a higher rate of egg deposition (numbers per m2) that some poor upland river that is mainly bedrock & peat and has water not much less acidic than Lemon juice.  Good local data is therefore the key to calculating good local Conservation Limits and the way forward will be to have the collection of such data included in all the local fishery management plans (its all in ours already). However, it will just not be possible to collect all the different types of data in all areas – Catch & Release and the closure of netting stations is a real problem here – so some data will have to be transposed from rivers where it can be collected to those where it can’t, which is quite an issue in itself. However, there is experience from other countries on how to handle these points and a good system will develop here over time, though the initial starting points, of necessity, have to be somewhat crude. Wednesday – on leave. Thursday – back in the office for the first time in 10 days, so a lot of admin catching up to do and also the weekly staff meeting as Nick away on Friday. Kenny has been on traps duty this week and with just a little rise in water, trout have been heading up into the Tweedsmuir trap, with six females there to start the season on Monday (and two Otter kills downstream – we have walk the stream to record these as well as those that actually get in to the trap in order to get a full picture). Unfortunately, a rise in water today was too much for my joinery and the new sluice gate that I’d made broke under the weight of water, but Kenny still managed to net some fish in and around the trap. Friday – started the day electric-fishing a sample of Salmon fry from the local Leader for study on the health of wild Salmon being carried out at Swansea University – luckily, the river not too high, though very peaty. Rest of the day catching up with admin and with James.