Bottom trawling in Marine Protected Areas

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Bird on a Fire
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Re: Bottom trawling in Marine Protected Areas

Post by Bird on a Fire » Tue Mar 02, 2021 5:59 pm

plodder wrote:
Tue Mar 02, 2021 4:40 pm
Have you read "an unnatural history of the sea"?

Lots of things about fishing are f.cked up
No, but I read Ocean of Life by the same guy. Super interesting stuff - especially the way the absolutely catastrophic declines in catches are masked by increased technology (bigger nets, travelling further afield, plus sonar, spotter helicopters etc) so they're not immediately obvious to many fishers who continue to peddle the "plenty more fish in the sea" line.

Much like the climate, it seems that present governance structures are completely inadequate to deal with threats to the global commons.


I don't eat any fish.
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Re: Bottom trawling in Marine Protected Areas

Post by Bird on a Fire » Tue Mar 02, 2021 6:02 pm

Matatouille wrote:
Tue Mar 02, 2021 5:08 pm
Goody, so a tech solution to address the physical damage would be fixing a problem that the fishers don't want solved. I guess I'll just continue to not eat flatfish then.
I think there are some trawling methods that stick to the very deep water just above the bed, rather than the bed itself, but finding decent information on how your fish was caught and whether it's sustainable is pretty difficult.

Marine Stewardship Council certification is better than nothing but AIUI there are some fairly big flaws. Simply not eating stuff is a better solution ;)
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Re: Bottom trawling in Marine Protected Areas

Post by Fishnut » Tue Mar 02, 2021 6:09 pm

There are various types of bottom trawling and the type used depends on what you're targetting and the size of the catch. The vessels I mostly worked on in the Falklands were factory ship bottom trawlers, averaging at around 40-50 tonnes per catch, 3-4 catches per day. They'd stay out for months at a time, coming in to dock only to change crews, offload fish and take on fresh supplies. One time we refuelled at sea which was pretty fun to watch. The vessels would go after squid during the two squid seasons and then switch to demersal fish the rest of the year. The gear looked identical from what I could tell, regardless of target species. The net would skim the sea bed behind two trawl doors. The top of the net would have buoys to help keep it open and sometimes the net would have fringes on the bottom which I assumed was to try and agitate the sea bed and prevent a barrier to fish trying to swim under.
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From what little I've seen of the UK fishing fleet it seems to mostly operate using more small vessels doing day-trips. Their trawls are smaller but that doesn't necessarily make them less destructive. Flatfish living in the sediment have to be scared out and that requires greater contact with the sea bed.

For shellfish such as scallops, dredging is used which is even more destructive than bottom trawling.

Personally I'd ban all fishing that comes into contact with the sea bed. It would mean the loss of some fisheries but I don't think we can justify the destruction any longer.
Bird on a Fire wrote:
Tue Mar 02, 2021 6:02 pm
Marine Stewardship Council certification is better than nothing but AIUI there are some fairly big flaws. Simply not eating stuff is a better solution
I was really supportive of the MSC but the more I hear about it the more dubious I get. It's mostly gossip I've heard at conferences and workshops so I have no idea about the validity of the criticism.

* I worked on one massive pelagic trawler that was almost 100m long and had 60-80 tonne catches which was an incredible experience, until the monotony set in which it did very rapidly. Despite the huge catches 95% was one target species, 94.95% was another target species and I'd be lucky if I got a couple of buckets of bycatch. The main target species also showed sexual dimorphism with the females being larger than males, and they were all spawning, so I could tell just by looking at them their sex and maturity without needing to cut them open (I always did, just in case). I could get biological data for 100 fish in less than an hour. 30 minutes for data entry and then I had 22 1/2 hrs to kill until the next shift.
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Re: Bottom trawling in Marine Protected Areas

Post by Squeak » Tue Mar 02, 2021 8:38 pm

I've seen enough of the fairly disastrous attempts at forestry stock assessments to be incredibly dubious about fish stock estimates. At least trees are large, visible from the air, and stationary. If scientists can't count them with enough reliability to not cause a crash in an industry, I cannot see how fish stock assessments could be any more reliable, even before industry lobbyists start working the refs.

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Re: Bottom trawling in Marine Protected Areas

Post by Fishnut » Tue Mar 02, 2021 9:59 pm

Squeak wrote:
Tue Mar 02, 2021 8:38 pm
I've seen enough of the fairly disastrous attempts at forestry stock assessments to be incredibly dubious about fish stock estimates. At least trees are large, visible from the air, and stationary. If scientists can't count them with enough reliability to not cause a crash in an industry, I cannot see how fish stock assessments could be any more reliable, even before industry lobbyists start working the refs.
Totally agree.

The thing I find challenging to understand is that fishing is, for a lot of people, one of those "my father was a fisherman, my grandfather was a fisherman, my great-grandfather was a fisherman, my son will be a fisherman and his sons will be too" industries, yet they seem to be, at least in aggregate, completely unwilling to accept that if they keep catching at the levels they have been there will be no industry for their descendents to work in. You'd think that people who have sat listening to their granddad talking about giant hauls while looking at the paltry catches they get would go "oh, something's wrong here" but instead they seem to stick their fingers in their ears and go "la la la I can't hear you". I know it's not all fishermen. I remember one captain wishing that we'd close the squid fishery as we were catching more bycatch than squid, and that bycatch was the food for the species he fished the rest of the year. But I also remember a conversation with a first officer who was convinced there was plenty of cod in the Grand Banks and the Canadians had only closed it because they didn't want the Spanish fishing in their waters.

The Grand Banks is actually an interesting case. From what I understand (and this is from a Canadian fisheries scientist rather than journal articles, so take with a grain of sea salt) though the cod fishery was closed, that only meant you couldn't target cod. There was nothing to stop you from catching cod as bycatch, and the amount of cod caught as bycatch has equalled or even exceeded the amount caught by the targetted fishery pre-closure. Suffice to say, cod is taking a really long time to recover there.

There's also the loss of genetic diversity which I'm reminded of after seeing this article that's just been published. Selective fishing has removed genes from the gene pool. Cod no longer reach the sizes they once did, and that's not just because they rarely get the chance. I don't think anyone (myself included) can truly grasp how big fish stocks used to be. Shifting baselines and short memories means that we quickly forget. "Plenty of fish in the sea" was a saying for a reason. Not any more.
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Re: Bottom trawling in Marine Protected Areas

Post by Bird on a Fire » Wed Mar 03, 2021 12:27 am

Squeak wrote:
Tue Mar 02, 2021 8:38 pm
I've seen enough of the fairly disastrous attempts at forestry stock assessments to be incredibly dubious about fish stock estimates. At least trees are large, visible from the air, and stationary. If scientists can't count them with enough reliability to not cause a crash in an industry, I cannot see how fish stock assessments could be any more reliable, even before industry lobbyists start working the refs.
I'd expect you to able to detect relative changes of a certain magnitude, because I'd expect most of the embuggerances with the counting would be constantish. At some point your index would wander outside your confidence intervals and you know something's up.

At least from a birds perspective. Let's say I'm counting the (Eurasian) Robins in my mum's small suburban garden (because I actually did this for years), and I never see more than two at once (because robins). One year I do banding there, and catch 50 individuals, so I know I'm way off (this actually happened). But if suddenly I never see more than one at once, or there's always one waiting on the shed roof, I know the population's changed. (A more gregarious flocking species would have been a better analogy for most fish, I suppose. Like tits)

The tricky bit comes when you have to put an actual number on it because you're setting quotas for catches. If there was sufficient variation in past catches and you have a long enough time-series you could probably correlate it with changes in the index, but otherwise I suppose you just have to decide between "this much is fine" or "definitely catch less than this" and see what happens, or use the blunt instrument of closed/open? I've seen quite a few studies of river fish (because populations are small enough for catch-mark-recapture to work well, unlike most sea fish, and I do lots of CMR stuff), but none of abundant sea fish, so I have no idea what they do actually.
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Re: Bottom trawling in Marine Protected Areas

Post by Bird on a Fire » Wed Mar 03, 2021 12:29 am

Fishnut wrote:
Tue Mar 02, 2021 9:59 pm
Squeak wrote:
Tue Mar 02, 2021 8:38 pm
I've seen enough of the fairly disastrous attempts at forestry stock assessments to be incredibly dubious about fish stock estimates. At least trees are large, visible from the air, and stationary. If scientists can't count them with enough reliability to not cause a crash in an industry, I cannot see how fish stock assessments could be any more reliable, even before industry lobbyists start working the refs.
Totally agree.

The thing I find challenging to understand is that fishing is, for a lot of people, one of those "my father was a fisherman, my grandfather was a fisherman, my great-grandfather was a fisherman, my son will be a fisherman and his sons will be too" industries, yet they seem to be, at least in aggregate, completely unwilling to accept that if they keep catching at the levels they have been there will be no industry for their descendents to work in. You'd think that people who have sat listening to their granddad talking about giant hauls while looking at the paltry catches they get would go "oh, something's wrong here" but instead they seem to stick their fingers in their ears and go "la la la I can't hear you". I know it's not all fishermen. I remember one captain wishing that we'd close the squid fishery as we were catching more bycatch than squid, and that bycatch was the food for the species he fished the rest of the year. But I also remember a conversation with a first officer who was convinced there was plenty of cod in the Grand Banks and the Canadians had only closed it because they didn't want the Spanish fishing in their waters.

The Grand Banks is actually an interesting case. From what I understand (and this is from a Canadian fisheries scientist rather than journal articles, so take with a grain of sea salt) though the cod fishery was closed, that only meant you couldn't target cod. There was nothing to stop you from catching cod as bycatch, and the amount of cod caught as bycatch has equalled or even exceeded the amount caught by the targetted fishery pre-closure. Suffice to say, cod is taking a really long time to recover there.

There's also the loss of genetic diversity which I'm reminded of after seeing this article that's just been published. Selective fishing has removed genes from the gene pool. Cod no longer reach the sizes they once did, and that's not just because they rarely get the chance. I don't think anyone (myself included) can truly grasp how big fish stocks used to be. Shifting baselines and short memories means that we quickly forget. "Plenty of fish in the sea" was a saying for a reason. Not any more.
Shifting baselines is a really weird one. It took me quite a few trips to Portugal before I realised how many more birds the English landscape would have held even a few decades ago. I mean I'd seen the graphs but hadn't really imagined what living among that many birds could be like. (Reader, I moved here)
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Re: Bottom trawling in Marine Protected Areas

Post by Bird on a Fire » Wed Mar 03, 2021 12:36 am

discovolante wrote:
Sat Feb 27, 2021 10:54 am
I think this action, like a lot of things of this nature (which often tend to be climate/ecosystem related these days) are basically a real life example of the trolley problem, except people are gonna spend ages arguing over how many people are tied down to which track.
You see, this is a much easier kind of stock to assess. People are generally big enough to see, and I assume people tied down to the tracks aren't going anywhere.

Get some marine scientists in and they'll sort that argument out pronto.
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Re: More Unlicensed Fly Tipping

Post by Bird on a Fire » Wed Mar 03, 2021 12:36 am

Woodchopper wrote:
Sat Feb 27, 2021 7:20 pm
I moved this topic to Weighty Matters as it contains an erudite discussion on marine environment policy.
I changed the title so that people know what the thread's about.

tenchboy u r 0wned
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Re: Bottom trawling in Marine Protected Areas

Post by bmforre » Wed Mar 03, 2021 3:14 am

Big cod not as big as they used to be

Article from Norwegian Public Broadcasting, in Norwegian. Plenty pictures showing Big Cod and text with historical and present-day info. Should be easy to read with machine translation. Documents and illustrates much of what has been discussed on this thread.

I grew up on the west coast of Norway, now live in a town on a fjord a bit more inland.

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Re: Bottom trawling in Marine Protected Areas

Post by Squeak » Wed Mar 03, 2021 3:57 am

Bird on a Fire wrote:
Wed Mar 03, 2021 12:36 am
discovolante wrote:
Sat Feb 27, 2021 10:54 am
I think this action, like a lot of things of this nature (which often tend to be climate/ecosystem related these days) are basically a real life example of the trolley problem, except people are gonna spend ages arguing over how many people are tied down to which track.
You see, this is a much easier kind of stock to assess. People are generally big enough to see, and I assume people tied down to the tracks aren't going anywhere.

Get some marine scientists in and they'll sort that argument out pronto.
Counting people tied to a railway track is definitely easier than even counting penguins (which are some of the easiest wildlife to count, due to being fairly big, with really tight phenology, and nesting in the open, where they mostly sit still while you count them.

BOAF - one of the challenges with trees is converting crown coverage into usable timber (height plus trunk size) which can be wildly variable within a single species and habitat type, even if the species is easy to ID on an aerial photo. I'd guess there are similar hard-to-parameterise issues with turning sonar pings into fish fillets.

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Re: Bottom trawling in Marine Protected Areas

Post by Bird on a Fire » Thu Mar 18, 2021 1:00 am

Bottom trawling releases as much carbon as air travel, landmark study finds
Fishing boats that trawl the ocean floor release as much carbon dioxide as the entire aviation industry, according to a groundbreaking study.

Bottom trawling, a widespread practice in which heavy nets are dragged along the seabed, pumps out 1 gigaton of carbon every year, says the study written by 26 marine biologists, climate experts and economists and published in Nature on Wednesday.

The carbon is released from the seabed sediment into the water, and can increase ocean acidification, as well as adversely affecting productivity and biodiversity, the study said. Marine sediments are the largest pool of carbon storage in the world.

The report – Protecting the global ocean for biodiversity, food and climate – is the first study to show the climate impacts of trawling globally. It also provides a blueprint outlining which areas of the ocean should be protected to safeguard marine life, boost seafood production and reduce climate emissions.

Only 7% of the ocean is under some kind of protection. The scientists argue that, by identifying strategic areas for stewardship – for example, regions with large-scale industrial fishing and major economic exclusion zones or marine territories – nations could reap “significant benefits” for climate, food and biodiversity. Protecting “strategic” ocean areas could produce 8m tonnes of seafood, they say.
So, um, could we really just not? There's plenty of other stuff to eat.
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Re: Bottom trawling in Marine Protected Areas

Post by bmforre » Fri Mar 19, 2021 5:30 am

Bird on a Fire wrote:
Thu Mar 18, 2021 1:00 am
So, um, could we really just not? There's plenty of other stuff to eat.
Fine that you have plenty to eat. But that's not true of everyone: Foodbanks seem to be busy in many localities.

There are many quality publications available on this and related subjects.
Here's one with authors from many countries involved with marine activities and research:

The footprint of bottom trawling in European waters: Distribution, intensity, and seabed integrity

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Re: Bottom trawling in Marine Protected Areas

Post by discovolante » Fri Mar 19, 2021 8:42 am

bmforre wrote:
Fri Mar 19, 2021 5:30 am
Bird on a Fire wrote:
Thu Mar 18, 2021 1:00 am
So, um, could we really just not? There's plenty of other stuff to eat.
Fine that you have plenty to eat. But that's not true of everyone: Foodbanks seem to be busy in many localities.

There are many quality publications available on this and related subjects.
Here's one with authors from many countries involved with marine activities and research:

The footprint of bottom trawling in European waters: Distribution, intensity, and seabed integrity
I dunno, I'm fairly sure BOAF is aware of the impact of poverty on choice and isn't directing his request at people who are having to use food banks.

People who do have the choice might want to deflect criticism by drawing attention to people who don't, though.
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Re: Bottom trawling in Marine Protected Areas

Post by bmforre » Fri Mar 19, 2021 10:50 am

disco, I see I was unclear and wrote about two issues using the term "this".

Issue 1: Not everyone has plenty to eat.
I am quitre sure boaf is well aware of that and just wanted to point out that not a few humans get too little protein to eat. Sustainable fishing yields valuable nutritionally needed food resources.

Bottom trawling is typically not sustainable.

Issue 2: Impact of bottom trawling.
The publication I linked to deals specifically with this.
I recommend it.

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Re: Bottom trawling in Marine Protected Areas

Post by Bird on a Fire » Fri Jan 14, 2022 11:45 am

Judge challenges the Government body taking Greenpeace to court over boulder dumping protest
The Brighton marine protected areas was established in 2016, but in 2019 it was said to be the most heavily fished UK protected area with nearly 7,000 hours of bottom trawling recorded.

The MMO launched a private prosecution saying that Greenpeace had acted without a licence.

However in a ruling on Wednesday Judge Bindloss, sitting at Newcastle Crown Court, said given their aims the two organisations “should be allies not antagonists”.

He had been told there was no evidence the granite boulders were actually harmful to the marine environment.

The MMO’s assessment had revealed that Greenpeace’s actions “were not dangerous.”

And he questioned whether the MMO should be “prosecuting in the name of marine protection”, asking them to consider whether the “licensing regime could be better used as a source of protection against those who actively seek to harm the marine environment”.

Greenpeace UK executive director John Sauven said it was a “bit of a mystery” why they were being prosecuted.

He said: “Our action was designed to safely protect nature from destructive fishing in an area designated as protected but where the MMO is miserably failing to do the job.

"We’re facing a climate and nature crisis and in response the MMO chose to bury its head in the sand, ignore the threat and prosecute Greenpeace.

“This is a clear signal for the Environment Minister to take the urgent action needed to protect our oceans from industrial fishing and ban destructive ships from all of the UK’s Marine Protected Areas”
https://www.yorkshirepost.co.uk/news/pe ... st-3525103
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Re: Bottom trawling in Marine Protected Areas

Post by jimbob » Fri Jan 14, 2022 6:08 pm

This is one reason why I'm in favour of far more offshore windfarms.

As well as acting as reefs, they must hamper such activities.
Have you considered stupidity as an explanation

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