Lots of dead fish on beach - Why?

werdnal · #1 (**permalink**) 12-08-2009, 08:47 PM

Went to a local beach on south coast of Cornwall today. Took our son rock-pooling and started to find a few dead fish. At first we only noticed small ones in rock pools - I guessed possibly having been stressed by frequent catchings by other children on the beach. Then we saw lots of immature flat fish being left behind by the ebbing tide - we dashed around catching as many as possible and putting them back in the sea or a large very deep pool that was likely to remain safe until the tide came back in.

The more we looked, the more dead fish we found, mainly small ones, but eventually even about half a dozen cuckoo wrasse - beautiful red and blue fish, and some others which someone identified as baby dog-fish, all unmarked but dead in rock pools or on the shoreline. One chap even hauled out a large conger eel from a pool, obviously dead.

Why so many dead fish on the beach? The weather has been pretty grim down here lately, but not stormy enough to drive so many fish onto the shore. It was quite distressing to see so many, although a couple of anglers were keenly collecting them for bait. Is it usual for fish to get stranded by the outgoing tide? Whats going on?

Marineboy · #2 (**permalink**) 13-08-2009, 09:35 AM

Not one I have come across so copied it to Glaucus and the Marine conservation society for their input.
I have come across numerous instances of dead fry in rockpools dead from oxygen depletion, but never anything like this.

Jim Ford · #3 (**permalink**) 13-08-2009, 09:37 AM

Quote:

Originally Posted by werdnal

Why so many dead fish on the beach?

Yet another piece in the 'Degredation of The Environment' jigsaw?

Jim

Gill Catton · #4 (**permalink**) 13-08-2009, 12:09 PM

this does sound very odd - almost like a chemical spill or something - but then it would be unusual I'd have thought to reach conger eels... I was going to suggest by-catch but would have thought there would be some marks of a net at least.... yes I too would find this concerning as it is not something I have ever come across either.... who deals with marine fish is it the Environment Agency if its so coastal? Either way I'd want to inform authorities and I don't suppose you kept any samples?

epops · #5 (**permalink**) 13-08-2009, 03:59 PM

Undersize and"rubbish" fish from trawlers? As for the conger saw a bloke down in newquay a couple of years ago hoy one over the side of his boat to them seals in the harbour so this too is obviously a"rubbish fish"????

Glaucus1 · #6 (**permalink**) 13-08-2009, 07:33 PM

Hello Andy,

Thanks very much for sending me this report.

Toxic algae, or more likely an accumulation of dying algae causing a
dissolved oxygen depletion is the most likely cause of mass deaths like
this.

Toxic algae warnings

Cheers

Andy Horton.
glaucus@hotmail.com
><< ( ( ( ' >
British Marine Life Study Society (formed 6 June 1990)
British Marine Life Study Society
----------------------------------------------------------------------
Marine life News Reports (NE Atlantic)
Marine Wildlife News of the North-east Atlantic Ocean 2008 (British Marine Life Study Society)
Marine Wildlife News of the North-east Atlantic Ocean 2009 (British Marine Life Study Society)

werdnal · #7 (**permalink**) 13-08-2009, 07:51 PM

Thanks for replies. Mystery has been solved on this evening's local news programme. It is an algae bloom - known locally as "red tide". A local fisherman was on the programme saying its more normal in April when the sea starts to warm up, but because of the naff summer, sea temperatures have been down until recently, so its come later, thus having such an impact on the immature fish which are closer to shore. Quite large numbers of fish have been affected, and washed up on several beaches around St Austell Bay area.

I guess the congor could have been a co-incidence being there at the same time.

Glaucus1 · #8 (**permalink**) 14-08-2009, 12:52 PM

Quote:

Originally Posted by werdnal

Thanks for replies. Mystery has been solved on this evening's local news programme. It is an algae bloom - known locally as "red tide". A local fisherman was on the programme saying its more normal in April when the sea starts to warm up, but because of the naff summer, sea temperatures have been down until recently, so its come later, thus having such an impact on the immature fish which are closer to shore. Quite large numbers of fish have been affected, and washed up on several beaches around St Austell Bay area.

I guess the congor could have been a co-incidence being there at the same time.

Hello,

Mystery has not been conclusively resolved. A best explanation has been found. I would be interested to know of the exact location of these deaths and the state of the tide please?

Other details like the possible presence of a freshwater stream running into the rock pools would also be of interest.

As I said before, toxic algae is the most likely explanation, but without precise details it is not 100%. Have you any pics please?

Cheers

Andy Horton.
glaucus@hotmail.com
><< ( ( ( ' >
British Marine Life Study Society (formed 6 June 1990)
British Marine Life Study Society
----------------------------------------------------------------------
Marine life News Reports (NE Atlantic)
Marine Wildlife News of the North-east Atlantic Ocean 2008 (British Marine Life Study Society)
Marine Wildlife News of the North-east Atlantic Ocean 2009 (British Marine Life Study Society)

Geoff F · #9 (**permalink**) 14-08-2009, 03:38 PM

Sewage contamination from an overflowing storm outfall is also a possibility.

What size of conger are you talking about? To me 'large' starts around 6ft and 30 lbs in weight. Many congers, including quite large specimens can be found in shallow water close to the shore.

Glaucus1 · #10 (**permalink**) 14-08-2009, 05:52 PM

With oxygen depletion, it is the larger fish that usually suffer first. This would happen with a toxic algae or a sewage leak. Direct poisons kill the small fish first.