A Fishy Tail

Last week's blog was about those special adaptations that ospreys have that make them so good at specialising purely on a piscatorial diet. This week we look in more detail at exactly which species of fish the Dyfi ospreys eat and what ratio of their diet each species makes up.

This morning my work colleague Alwyn and I were invited to give a presentation in Trawsfynydd (near Porthmadog), to the annual North Wales Fisheries Conference, specifically about ospreys and fish predation. Not an easy task you may think as these guys were there to discuss and explore ways of managing and mitigating against fish predation. Here's the video I had prepared for the conference to illustrate the main fish species that Monty catches: (watch in Full Screen and 1080P HD for best results!)




Great news - there was a seemingly unanimous feeling around the conference that the osprey was most welcome. Many fishermen and fishery workers came up to us at the end of the presentation to tell us about their encounters with the osprey either here or abroad. Many of the people at the conference this morning have emailed me over the years to tell me about an osprey they had seen at various lakes and rivers up and down north Wales. Good to put some faces to names too. Perhaps it is not so surprising that far from being the fisherman's enemy, the osprey diving down into the water and catching a fish can very often be the highlight of a fishing trip - it certainly beats the "one that got away" old chestnut! The statistics perhaps tell us why:

 

Total number of fish we recorded being caught by Monty in 2011 (click both charts to make them bigger)

The fish that have commercial significance here are the trout. Monty caught 119 trout in all in 2011 (102 Sea, 14 Brown and 3 Rainbow) - that's 29% of the whole catch. Here are the same statistics shown as a fish-pie chart:

So, around half were mullet, a quarter sea trout and a fifth flounder. I think that most people also realise that having ospreys around is a good sign that the environment is healthy and clean. Being at the top of the aquatic food chain, the osprey is a key indicator species that the habitat they live in is in good condition, and that means of course, there are plenty of fish around - everybody wins.
 

Fish delivery - Nora grabs a half eaten sea trout off Monty before he starts on the other half

This season we have again been recording fish data, only this time we have been including many other parameters as well. Temperature, tide, wind direction and strength, moon phase and so on. We have our own little theories as to why Monty catches the fish that he does and what criteria he uses for his prey selection decisions. We are glad to say that Aberystwyth University will be involved with this project also and will bring their own expertise to the table. The results should be fascinating, watch this space.

Humans and ospreys have been living side by side for hundreds of thousands of years, each bringing fish back to their families to ensure that the next generation is maintained. Judging by the fisheries conference this morning, this parallel coexistence is set to continue.

Talking of families, we may have a new family member, or two, or three, of our own on the Dyfi pretty soon. Look out for a blog and some HD images as soon as we see those eggs cracking open. Thanks to Vicky for the fish pie stats.