The easily recognisable three spined sticklebacks are the smallest of all the freshwater fish which inhabit the British Isles growing to an average length of only 5 to 8 centimetres, despite reaching such modest dimensions it is nevertheless an extremely aggressive predator, feeding on invertebrates and other small animals including tadpoles and smaller fish.

Spawning, Growth & Capture
Appearance, Habitat & Behaviour

With variable colouration ranging from a dark back of olive green shades subtly mingled with speckled brown hues merging into silvery flanks and a lustrous underbelly, on certain waters they may adopt a more sombre greyish mottled tone more in keeping with their local environs.

Rather unusually they are not scaled like most fish but instead display a variable number of armoured boney plates - scutes - along the length of their flanks. With a laterally compressed body and square set tail it takes on a rather stout pugnacious appearance in spite of its diminutive size and when you also take into account the distinctive spines set just in front of its dorsal fin - the number of which generally identify the species - its large oversized eyes, upturned mouth and pelvic fins bearing yet more protective spines, it is not a fish likely to confused with any other.

Although we are primarily describing the three spined species Gasterosteus aculaeatus it is only right that we also give a mention here to the nine spined Gasterosteus pungitius which although much rarer is also a resident of the British Isles. This species is also known as the ten spined stickleback though in actual fact the number of spines may vary with as many as twelve having been recorded in the past, similarly the three spined species has on rare occasions been recorded with two whilst four spines are not uncommon and even as many as five spines have been recorded. Whilst the nine spined species is both smaller and slimmer it is also more usually found in slow moving waters in the south and western regions of the country and is not widely distributed throughout Scotland with an encounter growing ever less likely as you travel northwards.

With the widespread nature of the stickleback giving the impression that is to be found in just about every water way throughout the land it is perhaps not too surprising that it has yet to receive any protection from a conservationalist perspective with only such morphotypes - diverging variations - as the spineless sticklebacks considered to be of any conservational value. These spineless variations, frequently referred to as 'anomalous' which put simply means deviating from the norm, are found within two SSSI's - Sights of Specific Scientific Interest - in Scotland at Loch Ruthven (East Highland) and Loch Druidibeg (Western Isles) although in both these instances it should be noted they are not listed as designated features of the site.

Though predominantly a freshwater species both three and nine spined sticklebacks are also to be found in brackish estuarine water where they adopt a much more silvery appearance and can tolerate high levels of salinity indeed in both fresh and saltwater environments they are one of the hardiest of fish well capable of thriving in low oxygenated and generally polluted areas where others would simply not survive.

Concentrating for now specifically on the three spined species - though there will naturally be some crossover detail common to both - it will happily take up residence in pond, loch, lake, gravel pit, ditch, stream or river though not being strong swimmers will avoid fast currents much preferring instead to frequent sluggish backwaters and stagnant areas where they can be seen swimming with their distinctive and rather unusual stop start motion, with short bursts of speed followed by a pause and much fanning of fins before once again they accelerate off in another direction.

A third British species - the fifteen spined Spinachia spinachia - is to be found exclusively within a marine environment, this slimmer species is considerably more elongated growing to between 14 and 17 centimetres and as the name suggests it bears fifteen spines although as before there are occasions when this may be one or two either side of that number.

Sticklebacks commence there extremely ritualised breeding courtship in early spring, generally late March through to early August, when the appearance of the males undergoes a dramatic transformation with throat and underbelly becoming suffused with an orangey scarlet colouration, eyes turning bright blue and chromed flanks reflecting a silvery lustre. These colours act both as a warning to other males to stay clear of its territory and also to attract females to its mound shaped tubular nest which it builds using its mouth, usually near the bottom intertwined with existing vegetation, from fine strands of aquatic plants and weed bound together with sticky mucous threads secreted from its kidneys.

It is interesting to note that sticklebacks are the only British freshwater fish to build nests from vegetation and it is solely the males responsibility for both nest building and the subsequent care of the young.

Once the nest has been completed the male sets about enticing as many females as he can to visit, on occasions resorting to harrying tactics if she shows reluctance, nipping at her fins and driving her towards the nest. After she has layed her eggs, sometimes numbering as many as 200, she will leave and he will immediately enter and fertilise the eggs, this process is sometimes repeated by the male who may successfully breed with several females either at the same nest or possibly using a second nest built elsewhere. The male then remains with the eggs which require high levels of oxygen during the incubation process so he continuously aerates them by fanning a stream of water through the tubular nest using his pectoral fins whilst at the same time aggressively defending the eggs from potential predators. After between 7 and 28 days the eggs hatch and he then continues for the next week or so to protect and care for the alevins in and around the nest until their yolk sac has been absorbed and his offspring can fend for themselves and disperse.

Outwith the breeding season sticklebacks can often be found shoaling in some suitably quiet backwater or sheltered bay and being omnivorous will consume all manner of invertebrates, worms, insect larvae, small snails, crustaceans, water fleas, small fish and even the eggs of their own kind are not safe from this largely nocturnal assassin who will likely be most successful during moonlit nights when it will become easier to detect their preys movement.

The life of the stickleback is a relatively short affair with an average span of only three to four years.

Although extremely unlikely to be targeted by the serious angler one may well be landed without actually being hooked having sucked into its mouth your offering of small worm or maggot intended for another species. In these circumstances the tiny sharp teeth of the tenacious stickleback will remain attached to the bait even after it has been lifted clear of the water, indeed if your worm offering is hooked though the middle this might result in two whoppers being landed simultaneously although their combined efforts are unlikely to put any significant bend in your rod !