A few years ago, in a post about a reconstructed fish weir–a fence used to trap fish–I noted that, historically, this was a good strategy:

Every year, a fishweir is reconstructed on the Boston Common (more information is available here). During the excavation and construction of Back Bay, a fishweir, thought to be about 3,700-5,200 years old, was discovered at what would today be Clarendon and Boylston streets–which then would have been a shallow marine intertidal zone. I bring up fishweirs because it’s important to realize what makes the large investment in building them useful: lots and lots of fish. You’re basically trapping fish against a fence and either spearing them or grabbing them.

For anyone who is familiar with New England salt marshes and seashores, this strategy seems ridiculous. When is the last time, in those habitats, you have seen enough fish (and minnow-sized fish don’t count) to justify this strategy? What many people don’t realize is that these habitats, until a couple of centuries ago were teeming with wildlife; in terms of productivity, these habitats are marine equivalent of Iowa farm soil. In Maine, lobster, in shallow habitats, were so plentiful, they were used to fertilize soil–and feeding lobster to servants, slaves or orphans in the 1600s was illegal (it was considered feeding people cockroaches). Ditto the fish.

Needless to say, we’ve changed those environments. Despite those changes, it’s safe to say these habitats and most of their species still exist, though many species have probably altered their behavior and physiology to compensate for human activity (e.g., cod reproduce at smaller sizes to produce offspring before being caught). On the other hand, there are habitats that we have essentially annihilated, such as the pre-European American prairie. The passenger pigeon is extinct, and the bison is a relict species.

Marine biologist Callum Roberts describes a similar abundance of riches (boldface mine):

Sardines were once extraordinarily abundant in the south-west of England, leading one 19th-century guidebook to say: “Pursued by predaceous hordes of dogfish, hake and cod, and greedy flocks of seabirds, they advance towards the land in such amazing numbers as actually to impede the passage of vessels and to discolour the sea as far as the eye can reach … Of a sudden they will vanish from view and then again approach the coast in such compact order and overwhelming force that numbers will be pushed ashore by the moving hosts in the rear. In 1836 a shoal extended in a compact body from Fowey to the Land’s End, a distance of at least 100 miles if we take into consideration the windings of the shore.” (Handbook for Travellers in Devon and Cornwall, John Murray and Thomas Clifton Paris, 1851).

Today people travel thousands of miles to dive and film such scenes, not realising they were once commonplace on our own coasts….

An abundance of small fish attracted the attention of larger creatures, as the above passage shows. Fishermen found the great herring shoals by following the “signs” of those better able to search for them: seabirds raining attacks from the sky, blowing whales, leaping dolphins, the thrashing of thresher shark tails; there was always a frenzy somewhere along the coast. The seas of the early 19th century and before had an exuberance of life it is hard for us to comprehend today, so long has it been since anybody saw it.

Huge fish also prowled the seabed. Common skate and halibut metres long and weighing 50kg or more were present in enormous numbers. Early photographs of fish markets around the UK show these fish covering the floor like great paving stones. Pictures of seaside towns show cod, ling and hake each more than a metre long laid out for sale after being caught from small boats within a few miles of shore.

There was a much greater diversity of large creatures in catches then. Animals such as wolffish, with their fabulous striped and spotted flanks, lurked in caves and rock piles.

And then we started clear-cutting the ocean floor:

Conger eels were abundant too. Our cartoon view of the conger eel now is of a toothsome beast whose eyes twinkle from the portholes of sunken ships. The reason that wreck fishing is one of the most popular forms of sea angling is that these places are avoided by bottom trawlers, giving them de facto protection. Where trawling occurs, congers are scarce.

It was bottom trawling that led to decline. Trawlers catch fish by dragging their nets over the seabed. It is not hard to imagine the damage this did to the great fields of invertebrates that lived on the bottom, including corals, sponges, seafans, sea nettles, oysters and hundreds of others.

While big fish were the mainstay of net and hook-and-line fisheries from the middle ages to the early 19th century, they declined rapidly with the spread of trawling, especially when steam power was added in the 1880s and 90s. A recent analysis of catch records shows that the amount of fish caught by trawlers for every unit of power expended has declined 25 times from the 1860s to the present. The simple reason is because there is less life in the sea.

Clear-cutting doesn’t really do trawling justice. Trawling is more like hunting for deer by lining up bulldozers and flamerthrowers on one side of a forest, and then smashing through the forest in order to flush deer out the other side. It is that destructive.

I realize food is a very personal thing, but I would rather have factory farming any day than the annihilation of the oceans. But unlike tropical rainforests, this occurs far from sight, so we don’t even realize what we’ve lost.

While this ultimately requires a structural, regulatory solution, as a consumer you can try to avoid destructively fished seafood.