Small-spotted catshark: life, behaviour and the long reads

Nothing about a small-spotted catshark is dangerous, and almost everybody handles one badly. Both things are worth explaining.

THE SKIN IS NOT SCALES. Sharks carry dermal denticles — small tooth-like structures with the same basic construction as teeth, pointing backwards. They are why the skin feels like fine sandpaper one way and smooth the other, why it was historically used as an abrasive, and why a catshark twisting against a bare forearm removes skin from it.

AND THE FISH WRAPS. A catshark is extremely flexible and its response to being held is to curl its body around whatever is holding it — an arm, a wrist, a hand. That combination, an abrasive animal with the ability to coil, is the whole reason unhooking one turns into a struggle.

SO REMOVE THE LEVERAGE RATHER THAN FIGHTING IT. Either hold the fish along its length with both hands, supported, with wet hands; or take a firm grip immediately behind the head with one hand and hold the tail with the other, keeping the body straight. Held straight, the fish can do nothing. Held by the middle, it does what it is built to do.

WET HANDS ARE NOT A FORMALITY HERE EITHER. A shark's skin carries the same mucus layer function as a bony fish's, and dry hands damage it.

USE A TOOL FOR THE HOOK. Long-nosed pliers or a disgorger. The teeth are small, but there are a lot of them and they are sharp enough to graze. If the hook is out of sight, cut the trace close and return the fish — that is a far better outcome than excavating.

AND RETURN IT PROPERLY, WHICH IS THE PART MOST OFTEN SKIPPED. Catsharks are widely treated as vermin: dropped on shingle, left flapping while the next rod is dealt with, thrown back from height off a pier. None of that is defensible, and none of it is necessary. There is no swim bladder to worry about, so a catshark returned quickly and gently does very well. Put it in the water rather than throwing it.

IF THE MARK IS PRODUCING NOTHING ELSE, MOVE. The honest response to a session where every cast produces a catshark is not to handle a hundred of them badly. It is to change ground, change bait, or fish elsewhere in the tide.

Most sharks bear live young. This one does not, and the difference explains why it is thriving while the tope and the spurdog are not.

THE EGG CASE IS THE MERMAID'S PURSE. A tough, translucent, roughly rectangular capsule with a long curling tendril at each corner. The female wraps those tendrils around seaweed, hydroids or other structure, anchoring the case where current will flow over it, and the embryo develops inside on its yolk for many months — longer in cold water, shorter in warm.

WHAT EMERGES IS A COMPLETE MINIATURE SHARK, around nine or ten centimetres long, able to feed immediately. There is no larval stage and no metamorphosis. This is a very different arrangement from the flatfish on the neighbouring page, which hatches as a symmetrical larva and is rebuilt.

THE EMPTY CASES WASH ASHORE IN QUANTITY, and for most people finding one on a strandline is their first and only encounter with shark reproduction. They can be told from skate and ray cases, which are larger, blacker, stiffer and carry horns at the corners rather than long curling tendrils.

AND HERE IS WHY IT MATTERS FOR THE FISHING. A spurdog carries a handful of young for two years. A tope produces perhaps thirty pups after a year-long pregnancy and matures late. A small-spotted catshark lays anchored eggs steadily over an extended season, matures earlier, and does not stake its entire reproductive output on the survival of a few large adults.

THAT IS THE WHOLE EXPLANATION FOR THE RED LIST CATEGORIES. In the same seas, under the same pressure, the live-bearing sharks are Vulnerable and Critically Endangered and this one is Least Concern. It is not that catsharks are tougher or luckier. It is that their reproductive strategy can absorb losses and the live-bearers' cannot.

WHICH IS ALSO A USEFUL WARNING ABOUT REASONING FROM ABUNDANCE. An angler who catches catsharks constantly might reasonably conclude that British sharks are doing fine. The species doing fine is the one being caught, and it is doing fine for a specific biological reason that does not transfer to the others.

Small-spotted catsharks are close to ubiquitous, which makes where they are a shorter question than what to do about it.

THE GROUND IS ALMOST ANYTHING. Sand, mud, gravel, mixed ground and the clean patches between rough — from a few metres of water off a beach down to several hundred offshore. Bull huss prefer rougher, rockier ground; the small-spotted catshark is the one on the open clean stuff.

THE SEASON IS ALL OF THEM. Fish are present around the British Isles throughout the year, with local movements that vary by area. There is no honest national calendar for this species, and it is precisely what keeps a winter session producing.

NIGHT IS BETTER THAN DAY, generally, and this is a fish that feeds actively in darkness using scent and electroreception rather than sight.

ANY BAIT WILL DO, WHICH IS THE POINT. Fish, squid, worm, shellfish, and anything dead. A catshark works a scent trail along the bottom and is entirely undiscriminating. This makes it a genuinely good species for a beginner — a bait on the bottom in the right area will produce a shark, which is not a sentence many countries can offer — and it makes it the bane of anyone fishing for something selective.

AND THE IDENTIFICATION PROBLEM IS THE BULL HUSS. The two are confused constantly, and every field guide's first answer — spot size — is the least reliable one, because spotting varies and worn fish are ambiguous.

THE ANSWER IS ON THE UNDERSIDE OF THE NOSE. Turn the fish over and look at the nasal flaps between the nostrils and the mouth. In a SMALL-SPOTTED CATSHARK the flaps are JOINED into a single continuous flap that extends down and REACHES THE MOUTH. In a BULL HUSS the two flaps are SEPARATE and DO NOT reach the mouth. That character does not vary with age, condition or wear, and it settles the identification every time.

SIZE IS A USEFUL PRIOR AND NOT A PROOF. A small-spotted catshark is usually 45 to 70 centimetres and around a metre at the extreme; a bull huss commonly exceeds that and reaches well over a metre and a half. A very large spotted shark is probably a huss — but check the nose.

NOTHING HERE STATES WHETHER THIS FISH MAY BE KEPT, what minimum size applies, or whether it is protected where you are fishing. Several British sharks, skates and rays are protected in some administrations and not in others, the designations are revised, and the answer differs between England, Wales, Scotland, Northern Ireland, the Isle of Man and the Republic of Ireland. Ask the fisheries authority for the water you are fishing before you go.

Unusually among sharks, the small-spotted catshark is oviparous: the female lays eggs rather than bearing live young. Each egg is enclosed in a tough, translucent rectangular capsule with a long curling tendril at each corner, which she wraps around seaweed, hydroids or other structure so the case is anchored while the embryo develops. Development inside the case takes many months, varying with temperature, and the young emerge as fully formed miniature catsharks of around 9 to 10 cm, already able to feed. Empty cases wash ashore in quantity and are the mermaid's purses found on strandlines. Growth is slow by bony-fish standards but the species matures earlier and produces eggs more steadily than the live-bearing sharks, which is a large part of why it remains abundant while they do not.

Egg-laying takes place over an extended season rather than in a short spawning window, with females depositing capsules a few at a time over months and attaching them to structure in relatively shallow water. Because the eggs are anchored, laid steadily and produced in reasonable numbers, this species' reproductive output is far less vulnerable to the removal of a few large adults than a spurdog's or a tope's. That difference in reproductive strategy — eggs on the seabed rather than a two-year pregnancy — is the single clearest explanation for why this shark is Least Concern in the same seas where the live-bearers are not.

An opportunistic bottom feeder and scavenger taking crustaceans, molluscs, polychaete worms, small fish and anything dead it finds. It hunts along the bottom by scent, working a trail rather than pursuing prey, and it is a persistent and undiscriminating taker of baits. For an angler this is the whole problem and the whole charm: a catshark will find and take almost any bait left on the bottom, which makes it excellent for a beginner and infuriating for somebody waiting for a bass.

Smell dominates, supported by the ampullae of Lorenzini that detect the electric fields of buried and living prey, and by a lateral line. Vision is functional but plays little part in finding food on a dark bottom. The practical result is that a catshark will locate a bait in any conditions — coloured water, darkness, strong tide — and that no presentation refinement will discourage one. If a mark holds catsharks, catsharks will find the bait.

Present around the British Isles throughout the year on almost all clean and mixed ground, with local movements between depths and inshore concentrations that vary by area rather than by a national calendar. There is no honest closed season for catshark fishing, and this is exactly the species that keeps a winter beach session producing when nothing else does.

The species most British sea anglers catch most often, and therefore the species on which most anglers form their handling habits — which is why it deserves a careful page rather than the dismissal it usually gets. It is an excellent first shark: abundant, small, harmless, present year-round, and completely undemanding about bait. It is also the fish that teaches an angler that a shark is a different animal from a bony fish, if anybody bothers to point it out.