What hook size for which fish, and why there is no single answer

The bait sets the floor. A point buried in a bulky bait does not reach the fish, which is the commonest reason a bite produces nothing; a hook so small that it slides inside a worm bait is often swallowed with it, which is bad for a fish you mean to return. The same hook in a small bait looks unnatural and is dropped. So the starting point is the bait you will use, threaded or tied on as you will fish it, and a hook whose gape stays clear of it.

The expected size of fish sets the ceiling. Sea Angling Ireland's author rarely goes above 4/0 for mid-sized fish, having lost them on bigger hooks, and puts it plainly: the bigger the hook, the more fish are taken out of the equation and the more bait must go on it. British Sea Fishing makes the same point from the other side: cod anglers step up to large hooks partly so that small whiting cannot take the bait.

The ground decides the pattern. Over rough ground a strong, forged pattern holds a heavy fish and resists opening out; over clean sand a finer wire penetrates more easily.

Both sources give cod a large, strong hook. British Sea Fishing gives 3/0 to 6/0 in a strong pattern, often two in a pennell so a big bait is held and a fish that takes it is hooked. Sea Angling Ireland calls 4/0 standard, with much bigger used for big baits, and drops to 2/0 where the fish coming in are smaller — codling need a smaller hook and bait, but not too small. The baits these sizes go with are big: peeler crab, lugworm in bunches, squid, mussel, whole or half mackerel, and cocktails of them.

So: about 2/0 for codling on worm, 3/0 to 4/0 for most shore cod baits, and up to 6/0 for whole squid or fish baits for big cod.

Whiting have smaller mouths and are caught on smaller hooks. British Sea Fishing suggests about a size 1, or 1/0, on a two-hook flapping rig with worm or mackerel strip. Sea Angling Ireland sets the limit rather than a size: at or below 2/0. Both note the converse, and it is the useful part for a cod angler: a 4/0 to 6/0 is the only real way to keep whiting off a cod bait. British Sea Fishing adds that whiting are delicate and do not survive unhooking well, so any meant to go back should be handled as little as possible.

Bass are where the hook most visibly follows the bait. Planet Sea Fishing's author starts worm baits on a surf beach at 1/0 or 2/0 and works up or down to suit the bait; puts a whole peeler crab on a pair of 3/0 or 4/0 hooks; and uses a 5/0 for live joey mackerel. Sea Angling Ireland gives 2/0 upwards, with a pennell a must for crab.

So: 1/0 to 2/0 for worm on the open beach, 3/0 to 4/0 on a pennell for crab, larger for live or dead fish baits.

Mackerel have small mouths for their speed, and both sources favour small hooks. British Sea Fishing gives 1/0 or 2/0 as usual on shore feather and daylight rigs, and a size 1 or 1/0 for a float-fished strip bait; Sea Angling Ireland says that on feathers the smaller the hook the more fish come, and that big 5/0 or 6/0 hooks are a waste of time. Feathers sold for cod from a boat can carry hooks up to 6/0, which is why the packet is worth reading.

Sea Angling Ireland treats 1/0 as a small sea hook suited to flatfish, mullet and small baits, and keeps really small hooks — a 6 or an 8 — for sole, whose mouths are tiny for their size. British Sea Fishing's plaice page recommends long-shanked hooks such as Aberdeens or specialist flatfish patterns, which hold a worm bait straight and come out of a small mouth more easily. These are one source each on size, and are reported as such.

Hook rules are set where you fish. On many fisheries barbless hooks are a condition of fishing at all, and a club's or fishery's rules may say more about hooks than that; read the permit or the rules before fishing. Some rules are statutory: a NOAA Fisheries bulletin of February 2017 records that circle hooks are required when fishing with natural bait for reef fish in federal waters of the Gulf of Mexico. That is one example, dated to the bulletin, and not watched here for change; check the current rules for any water you fish.