It’s been an exciting morning here at Lakenheath Fen – the fish arrived!
4,000 rudd appeared under the supervision of Chris from Framlingham Fisheries, near Ipswich. During transportation they were supplied with oxygen directly into their water supply. An aerator can be used as well but these create quite large bubbles. As our fish are only one to two years old and therefore quite small, the aerator wasn’t used because the big bubbles can cause damage to the fish. It’s hard to imagine bubbles causing harm to anything but here is a photo to show the size of our little fish at the moment. They will grow of course, up to approximately eight inches in length.
Photo credit: Dave Rogers – two rudd in the hand
The rudd look quite silvery with a hint of yellow at the moment, with very little red to their fins. This is due to the quite clear water conditions in which the fish have been raised and the container they were transported in. The waters here at Lakenheath are different and contain more tannins, which makes the water slightly orange/brown. Once the fish have acclimatised they will change colour to become more camouflaged within their new surroundings. You can see they show up quite clearly in the photos and they will also be quite obvious to their predators, so they will quickly lose some of the yellow tinge and will get more red on their fins too.
Photo credit: Dave Rogers – the rudd will change colour to suit their new habitat
The fish were distributed into areas of the reedbed where we know our fish stocks need some help. We are regularly visited by the RSPB ecology team who carry out electrofishing surveys and this information guides our management. The areas with fewer fish are also those with less established aquatic plants, which is something we are trying to improve upon. In the meantime, these locations are where we are putting our new fish refuges to provide a bit of extra cover for our new fish.
We also released approximately 500 fish into the pool in front of the hide. Some lucky visitors saw this taking place and we all watched as the rudd swam serenely around in the ditch by the hide before Chris ushered them out into the pool. They would have found their own way eventually but we thought we’d help them get into some better cover. As we walked along the boardwalk we could clearly see the amount of life there is in the water, such as cased caddisfly larvae and water fleas. Even if they hadn’t found their way out of the ditch immediately, they would have had plenty of food to see them through.
Photo credit: Dave Rogers – rudd into the Mere Hide pool
As we continued back down the boardwalk a bittern started booming right across the pool! We couldn’t see it but it was pretty close by. As long as he doesn’t eat up all the new fish straight away we should all be happy. The fish should start to spawn after about two to three weeks and then we’ll have the next generation started too. We’ve just got to hope that the fish look after themselves within the reedbeds and ditches. It was a little frustrating to watch at least three of our newly released rudd get snapped up by a large pike who had been lurking nearby in one of the release locations. Apparently those three fish will keep the pike going for quite a while, hopefully giving the other 997 time to make a run for it into the cover of the fish refuges and vegetation!
As we made our way down the reserve delivering our fish in the sunshine, there were hobbys everywhere feeding on dragonflies and other airborne insects. Marsh harriers swooped over the reedbeds and we heard two more bitterns booming as well as bearded tits pinging at one of our drop off points. What a fabulous way to spend the morning!
Photo credit: Dave Rogers - rudd into our beautiful reedbed