Ally wrote: ↑Sun Nov 03, 2019 9:30 am
DaceAce wrote: ↑Sat Nov 02, 2019 9:30 am
The main change to the ecology of the Avon in the last 10 years has been the cessation of mechanical weed cutting in 2010 and this factor alone has had far more impact on roach (and other species) numbers than the effects of the ARP. The summer volume of the Avon below Salisbury has more than doubled, carriers have depth again, water temperature is higher and there is far more cover for the roach in summer, some of these factors to the detriment of salmon.
Yeah what I always thought weird about arp is if the river couldnt support the fish how would shoving a load more in help.
I
think (and I’m no expert) the main thrust was based upon the fact that the fish surveys were showing that the roach populations in many reaches (i.e. mill to mill) had crashed to below critical levels - in other words, even if other factors like cormorant predation* were removed, there were simply not enough roach left to regenerate the population naturally (given survivability rates).
What the ARP did was to encourage the roach that were left to spawn on the artificial boards and removed that spawn to the hatcheries and growing on ponds. That meant that the survivability if the hatchling roach went from (say) one in one hundred to ninety percent. They then successfully raised those roach to return them to the river in their thousands. Repeating that and then with those returned roach spawning and regenerating the population once again had the springboard to create sustainable populations again.
I suspect that the reality is that this has been a combination of the ARP
and numerous other factors including those mentioned. Whatever the truth, and we’ll never know, reality is that you can go to the Avon this weekend and dream of catching roach again like this ten ouncer - look at the shoulders on that:
*considerable action has been taken on this front along the valley, as I understand it.