My own connection with the sea is through swimming, and it was while dipping  in the Firth of Forth that I first became interested in the life of those East coast waters. I began to hear stories, to learn how the rare oyster shells washed up on the beach were old because in the Firth these days there are no native live ones. The once giant oyster reefs were gone. We long ago overfished them. Only now is a project starting to rewild those waters, with oysters in tiny numbers.

From the Forth, I became interested in the Clyde, because the stories of overfishing were similar, though the sea seemed more intensely studied. Once great fisheries of whitefish had collapsed. Herring shoals had been replaced by sprats. Cod had dwindled. Haddock, well haddock is looking on the up, and prawns, great big langoustines, are thriving in great abundance.

The Clyde, according to a landmark paper titled Ecological Meltdown in the Firth of Clyde, published in 2011 had stated was a “marine desert”. But was it really? Or was it more like ‘used, degraded agricultural land in need of restoration’, as a Scottish Government Clyde Ecosystem Review worded it? And had it since then improved?

Whatever the case, it’s clear that the last half century has seen losses at sea. The biomass, as the Clyde Ecosystem Review states, is the same, but its populations have altered. Large fish have been replaced by smaller fish, and an abundant prawn fishery. It's not the same seascape it once was  - and in the backdrop of all of this has been fishermen, fighting to still make an income, and adapt to changing demands, quotas and marine protections.

Fish matter because they feed us, and feed others as exports. But they are not just stocks, as we often call them. They are also, in a world where biodiversity is in decline, species to be valued for themselves, and their role in their ecosystems. Their loss is not just a loss from our larder - and most of those I spoke to for these articles, fishermen and conservationists, see it that way.

But nevertheless there is a lot of heat around the Clyde. Of all the conservation strategies perhaps the most controversial has been the Clyde cod box. A policy of seasonal closure to whitefish trawling during the spawning season, once backed by fishermen, became a source of anger and despair when it was abruptly extended to include creel fishermen, trawlers and scallop dredgers.

The atmosphere has been fraught. How the cod box closure was handled fostered distrust and fed into reactions to last year’s HPMA consultation. Marine conservationists and fishermen who once regarded themselves as on the same side now seem stuck in silos. Often those in the fishing industry rail against what the environmental groups they call the ENGOs.

Alongside these changes in fish has also been a decline in numbers involved in the fishing industry. Fishermen will often say that they are the ones in need of protection.

We look into the story of cod and trawlingWe look into the story of cod and trawling (Image: AFP via Getty Images)

The result is a breakdown in communication. Workers in the fishing industry, particularly those who have been responsible for driving forward sustainability policies like the Clyde cod box, feel got at.

Campaigning groups feel that their messages are being dismissed simply for being campaigns, with scientific points ignored, rather than taken seriously, The Marine Directorate, seems to hover, aloof, its science underfunded, even as many in the fishing industry volunteer to collect more data.

Read more:

Clyde cod: 'I thought closure was a joke. Government won't do that'

The Clyde cod tragedy. Will once common fish ever recover?

And meanwhile, almost everyone says it’s the science that matters. That is particularly the case with the Clyde cod. It matters to fishermen because they want to see a thriving sea, but also because they don’t want to see measures that reduce their ability to fish based on science in which they do not have confidence.

It matters to marine scientists, who believe that sometimes the very best, most relevant science, is not what is being used to inform policy, and that the government’s Marine Science laboratories in Aberdeen have been chronically underfunded.

It matters to campaigners who will often express a belief that policy is driven by industry, not science. Indeed, this is a gripe that most groups share, a suspicion that policy decisions are triggered by politics and influence, lobbying and funding, not the scientific knowledge base.

The idea behind this series has been to listen to both sides, dig into the data, examine the success and failure of policies, and find stories of hope, both among fishermen and marine conservationists, including trawlermen like Ian Wightman, a pioneer who strives hard to test new technologies to minimise bycatch and collect data, and make his fishing as sustainable as possible, to the conservationists behind Arran COAST’s marine reserve and No Take Zone.

As a swimmer, I am someone who floats on the surface, even when I go snorkelling as I did for this series, it's close to the shoreline, but some of those we have spoken to have been sea-goers know the Clyde a deep way, many of them having observed the shifts in its waters and life over time, or scientists who have trawled the data for pearls revealing what goes on in the depths.

The Clyde is just one story of marine life and an inshore fishery and our relationship to it - there are many more. This series hopes to see what we can learn from it, what answers it points to in terms of marine protection and fishery policy.

How do we, in the Clyde and elsewhere, protect both fish and fishermen?