The end of an epic journey

 We found this dead salmon, on Christmas Eve, in Waskerley beck, a tributory of the river Wear at Wolsingham in Weardale. It had evidently swum upriver from the sea to spawn in shallow gravels and died of exhaustion, old age or disease - or perhaps from all three causes. Patches of fungal disease are clearly evident on its scales. Few salmon make it back to sea after they have spawned.

It would have begun life in the river as an egg, made its way downstream to the North Sea, then spent up to four years in  the sea before returning to its home river to spawn. The end of an epic journey.

What an otter ate

I have a favourite flat rock to sit on, on the banks of the river Tees where it meets the river Greta downstream from Egglestone. It's the perfect place to watch kingfishers as they flash past. Last week when we arrived there we discovered that an otter had decided to use it as a latrine and had left a substantial pile of poo, or to be more correct, a spraint.

There was no mistaking what it was - it had that characteristic oily, sickly smell - even though a few days of heavy rain had washed away its greasy coating. When we had a close look we could see the indigestible remains of the otter's meals embedded in it. 

A close look revealed some white circular objects and also the jointed antennae of a signal crayfish, confirmed by the presence of ...

... two large crayfish claws nearby which had been cracked open to extract the flesh.

I took the spraint home, soaked it in detergent overnight and extracted some of the remains of the food items.....

... Most of the objects on the left hand side are fragments of crayfish limbs and the larger object in the middle is part of its telson - the end of the abdomen that is usually curled under the crustacean and has flat fan-shaped paddles on the end. With one powerful flick of this it can propel itself backwards if threatened - although it didn't do this animal much good when it met the otter.

The long, thin object is one of the crayfish's antennae, still articulated after its passage through the otter's gut.

What interested me most though were those six pale objects down the right-hand side of the picture. They are otoliths - the 'earbones' of a fish that are part of its system for perceiving gravity and acceleration when it swishes its tail fin and shoots forward - not fast enough, in this case. The largest otolith is about seven millimetres in diameter, suggesting that the otter had caught quite a large fish.

The otoliths, seen under a magnifying glass, are fascinating structures made up of layers of calcium carbonate. You can see the concentric layers quite clearly here in two planes, because this otolith has been broken when the otter chewed the fish. 

The calcium carbonate comes from the water and the different coloured layers reflect differences in the chemical composition of waters that the fish swam in during its lifetime.

So, this little pile of smelly poo held some interesting clues to the otter's diet. Now I know that it has a territory here we'll be going back to see if we can watch the animal in action.

Right time, right place, wrong gear ...

A recent photograph on Flickr by Bob the Bolder showed a salmon leaping the wear on the River Wear just below Durham cathedral in mid-August, which is early for these fish to start moving up river to spawn. 


One October afternoon five years ago I happened to be walking past Spurleswood beck in Hamsterley forest in Weardale just at the time when salmon were trying to leap the waterfall there. We watched for half an hour while fish after fish hurled itself into the torrent but none made it to the top. Conditions were probably close to perfect for the fish, with the beck in spate and a deep plunge pool below the waterfall where the upwelling water would have given the fish extra impetus, so maybe some made it after we left. 

It's hard to be sure whether these were sea trout or salmon but judging from the indentation in the tail fin I think they were salmon. Sea trout tend to have a straight trailing edge to the tail fin.

I didn't have any decent photographic gear with me when I took these bu,t judging by Bob the Bolder's photo, now is the time to plan for a return visit............

Not for the squeamish ....

This rather unpleasant looking fish is a hagfish Myxine glutinosa, a member of a very ancient order of jawless fish. They live in muddy sediments and feed on dead and dying fish, sometimes burrowing through their flesh and consuming the fish from the inside out. They've also been found inside of human corpses that have been in the sea for a long time.

I've twice found these unlovable fish on the shore, alive, along the North East coast. The first occasion was at Whitburn Rocks in Tyne and Wear (see pictures at the bottom of this post) and this one was on the Alnmouth end of Warkworth beach in Northumberland. Both locations were close to river mouths and I suspect that had been thrown overboard by fishermen cleaning their catches on their way into port.

Hagfish are blind, although they can perceive light, and they find their prey by scent, using the barbels on their nose. Aside from their feeding habits, their most unpleasant characteristic is that they release massive amounts of slime when they are caught - you can watch this here on YouTube. This is sufficient to deter an attacking shark - see this YouTube video. Even more remarkably, these fish can tie themselves in knots because they have no rigid vertebral column.

This is the mouth, with tooth-like projections inside that the hagfish uses to chew a hole in the body wall of dead fish. That 'knot-tying' behaviour allows it to twist and turn, tearing a hole in its prey.

Nice.

These are old pictures - I took them in 2007.

You can read more about hagfish here.

Something fishy going on ....

This shoal of grey mullet were swimming in the sunlit but slightly murky waters of Sunderland Marina, at the mouth of the river Wear, this afternoon. This is eleven of the fifteen in the shoal .....

.......... lovely streamlined fish .........

... with slightly iridescent scales (double-click for a larger image).

When the Boat comes in.......

I like places that celebrate their heritage. This cavorting fish....

..... pursued by a long line of similar-shaped ridge tiles chasing its tail ......

.... and the fish motif on the street lamps..

.... and on the end of the public benches on the quay, where you can sit and eat your fish and chips, mean that you could only be ......

... in North Shields

Spot the Shrimp.... and Mind where you Tread!

At this time of year the pools of water left on sandy beaches at low tide are full of shrimps, although you need to look very carefully to spot them. This one, given away only by its white legs, was hidden in a pool on the beach at Warkworth in Northumberland last weekend. Double click on the picture for a larger image and you can just make out its tail, on the left, and the pair of stalked eyes (with a white mark between them) that protrude above the sand when it buries itself. The speckled pattern on the exoskeleton of the animal provides almost perfect camouflage

In this enlarged image, above,  you can see the eyes and legs a little more clearly....

Anyone going shrimping on a sandy shore would be wise to wear shoes when they wade in the shallows at this time of year because venomous weever fish feed on shrimps and when the water warms up they come inshore to catch them. This one was partially buried in the sand on Warkworth beach.

The three spines on the dorsal fin, seen erected in this disgruntled lesser weever Echiichthys vipera , are tipped with venom that causes excruciating pain for anyone who treads on one with bare feet. A trip to the beach then ends with a trip to the local A&E hospital. I rescued this fish from a gaggle of gulls that were attacking it in the shallows but were still very wary of it.

Despite their evil reputation for inflicting pain, weever fish have the most beautiful emerald eyes, set in a gold circlet. Usually the fish would be more deeply buried in the shallows, with just eyes and spines above the sand.

You can read more about weever fish at http://www.marlin.ac.uk/speciesinformation.php?speciesID=3221

Sticklebacks

The walkway built out over the new wetland area at Durham Wildlife Trust's Low Barns Reserve at Witton-le-Wear offers excellent opportunities for watching the courtship dances of sticklebacks in spring. A male fish builds a tubular nest in the shallow water from bits of weed, then defends his territory from other males until he's enticed a female to swim through his nest and lay eggs inside. Males guard their nests, fanning water over the eggs, until they hatch. You can watch movies of the whole sequence at

http://www.arkive.org/three-spined-stickleback/gasterosteus-aculeatus-aculeatus/