Haddock

Haddock occupy cold north Atlantic shelf waters and are more strictly demersal than the cod they are usually grouped with.

THEY STAY NEAR THE BOTTOM. Unlike cod, which will move up through the water column, and saithe, which hunt in midwater, haddock feed on and just above the seabed and rarely leave it. That is why they are taken on baits fished hard on the bottom and comparatively rarely on lures worked high.

SOFT AND MIXED GROUND IS THE PREFERENCE — sand, mud, gravel and shell rather than heavy rock and reef — because their diet is dominated by benthic invertebrates: worms, brittlestars, small crustaceans and molluscs, taken from and within the sediment.

THEY HAVE A SMALL MOUTH FOR A GADOID, which is the physical reason for that diet and the reason haddock are taken on smaller baits and hooks than cod from the same ground.

DEPTH IS TYPICALLY FROM A FEW TENS OF METRES TO SEVERAL HUNDRED, and it is size-structured, with larger fish generally deeper.

COLD WATER IS THE REQUIREMENT. Haddock are a boreal species, most abundant in the northern North Sea, around Iceland, the Faroes and the north-west Atlantic, and scarce at the southern edge of the range.

JUVENILES ARE PELAGIC BEFORE THEY SETTLE, drifting in the water column for months before adopting the bottom-associated adult habit, and the success of that settlement drives the enormous variability in haddock year-class strength.

AND THAT VARIABILITY IS THE FISHERY'S DEFINING FEATURE. Exceptional year classes recur irregularly and dominate the stock for years afterwards, which is why haddock abundance swings more than most demersal stocks and why assessment for the species leans heavily on recruitment surveys.

Haddock present an unusual combination: a fish that is easily damaged in the mouth, taken from depths that guarantee pressure injury, in a fishery where quota and size rules generate discards.

THE MOUTH IS THE FIRST PROBLEM. Haddock have soft mouth tissue and are frequently hooked in a way that tears. Multi-hook rigs worked at depth compound it: a fish that is hooked, then dragged while the remaining hooks are baited or while other fish are played, arrives with damage that has nothing to do with how it is handled on deck.

THE DEPTH IS THE SECOND. Haddock are physoclistous and taken from depths where swim bladder expansion is severe. The stomach eversion and buoyancy familiar from other deep species occur here too, and a haddock returned at the surface commonly floats.

WHAT FOLLOWS. This is realistically a retention fishery, and the useful handling intelligence is about not catching fish you cannot keep: fish fewer hooks, use hook sizes that select against undersized fish, and move off a mark that is producing small fish rather than working through them. Selectivity at the rig is worth more than care at the rail.

ON DECK the fish is harmless — no teeth of consequence, no venomous spines, no significant handling risk to a person. The dispatch, if the fish is being kept, should be immediate and the fish chilled, because haddock flesh degrades noticeably faster than cod's.

AND THE BOAT IS THE ACTUAL DANGER. This fishing happens offshore, in cold water, often in poor conditions, with heavy leads swinging on deck. The fish will not hurt anybody. The circumstances routinely do.

Haddock have an unremarkable seasonal pattern and a very pronounced daily one, and for an angler the second is far more actionable than the first.

THE SEASONAL PATTERN IS THE NORTH-EAST ATLANTIC GADID STANDARD. Movement to deeper spawning grounds in the colder half of the year, movement back to shallower feeding areas afterwards, with the recreational fishery generally following that inshore movement. It is driven by temperature and by the spawning requirement, it applies on a northern-hemisphere calendar throughout the species' range, and it is genuinely similar to what cod and whiting in the same water are doing.

WHAT DISTINGUISHES HADDOCK IS WHAT THEY EAT AND THEREFORE WHERE THEY ARE. Haddock feed predominantly on benthic invertebrates — brittlestars, worms, molluscs, crustaceans — rather than pursuing fish the way cod do at the same size. That ties them much more tightly to particular bottom types: clean sand, gravel, shell and mud where their prey lives, rather than to the rough ground and structure a cod uses. A haddock mark is a description of a seabed, and it does not move.

SO THE SEASONAL QUESTION LARGELY RESOLVES INTO A DEPTH QUESTION. The same ground is fished; the fish are on the shallower end of their range or the deeper end of it depending on the time of year and the water temperature.

AND THE TIDE GOVERNS EACH SESSION. A bottom-feeding fish over an offshore mark is fished at anchor or on a drift, and both are constrained by flow: too much tide and a bait cannot be held on the bottom at all, too little and a drift does not cover ground. That practical constraint is why boat fishing for haddock has a rhythm tied to the tidal cycle and to the spring–neap cycle, and it is a constraint on the boat rather than on the fish's appetite — a distinction worth keeping clear, because it is routinely reported as though haddock feed on a particular state of tide.

Haddock reproduction explains one of the most distinctive features of the North Atlantic fisheries: the enormous, irregular year classes that dominate a stock for a decade.

SPAWNING IS A BROADCAST EVENT ON OFFSHORE GROUND IN LATE WINTER AND SPRING. Mature haddock gather on known spawning grounds and release eggs and sperm into the water; the eggs are buoyant and rise, and the larvae drift in the plankton for a period before settling. There is no nest, no care and no defence of anything.

FECUNDITY IS ENORMOUS AND THAT IS THE MECHANISM BEHIND THE VARIABILITY. A large female haddock releases a very large number of eggs, of which an almost vanishingly small fraction survive to recruit. When conditions in the plankton happen to align — the right food at the right time, the right transport, the right temperature — survival can be an order of magnitude better than usual, and the result is a year class large enough to dominate the stock for years. Several North Atlantic haddock stocks are effectively defined by a handful of such years.

WHICH MEANS RECRUITMENT IS ONLY LOOSELY RELATED TO SPAWNING STOCK SIZE. A big spawning stock improves the odds; it does not produce a big year class on its own, because the bottleneck is larval survival rather than egg supply. That is why stock assessments for this species treat recruitment as a highly variable input rather than as a predictable function.

THE MALES DRUM DURING COURTSHIP, which is worth stating because it is a real and well-documented behaviour: haddock produce sound using muscles against the swim bladder as part of spawning display, and the sound is part of how mates are found on a spawning ground. It is also, incidentally, a reason underwater noise is a genuine concern for the species.

MATURITY IS REACHED WITHIN A FEW YEARS and females grow larger and are more fecund with size, so the age and size structure of the spawning stock affects its reproductive potential and not just its biomass.

AND WHAT MAY BE CAUGHT IS AN ASSESSED AND NEGOTIATED MATTER, revised annually and differing between sea areas. Nothing above indicates what any current rule is.