FRESHWATER LABORATORYFaskally, Pitlochry,

Perthshire, PH16 5LB

www.scotland.gov.uk/marinescotland

TOPIC SHEET nO. 45 v1

/ / p ike

IntroductionThe pike, Esox lucius, is a predator which feeds extensively on fish, although it also eats a range of other animals, including insect larvae, frogs, water rats, and ducks. The pike is usually green and silver in colour, with distinct dark striped markings on the flanks to afford good camouflage. Markings vary, and can be used to distinguish among individual pike.

ThehunterThe pike’s body form is well-suited for its predacious habit. The body is elongated, and large fins are set near the tail to increase the surface area pushing against the water during the explosive lunges at prey. Much of the routine movement is achieved by sculling motions of the paired fins on the underside of the body. These fins gently manoeuvre the pike into position for attack. The eyes swivel to stay fixed on the prey and the body tenses into an ‘S’

shape. As the body unwinds and the pike accelerates forward, the mouth opens to engulf the prey fish, which is usually captured sideways on. The pike’s large bony mouth is armed with rows of teeth. These point backwards and hinge to allow the prey to slide into the gullet, but ensure that there is little chance of escape. The prey is usually turned so that it is swallowed head-first.

Pike tend to be sprinters. Their muscles are designed for rapid bursts of activity but their capacity to swim at moderate speeds for long periods is much reduced as a consequence. They have evolved an energy-conserving strategy, having a low resting metabolic rate, and even at full stretch do not raise their aerobic metabolism* substantially, compared, for example, with salmon and trout. For a young pike, the effort of digesting a large meal is literally exhausting and induces maximum heart rates.

*AErOBIC METABOLISM CAn BE MAInTAInEd FOr LOng PErIOdS By COnTInuALLy SuPPLyIng OxygEn TO THE TISSuES, And IS ASSOCIATEd wITH FAST BrEATHIng And HIgH HEArT rATES In PIkE And HuMAnS. AnAErOBIC METABOLISM OCCurS durIng ExPLOSIvE BurSTS OF ACTIvITy And rEquIrES A SuBSEquEnT PErIOd OF AErOBIC ACTIvITy durIng rECOvEry.

PHOTOgrAPH © dAgMAr & wOLFgAng FrITz, uSEd wITH PErMISSIOn.

FRESHWATER LABORATORYFaskally, Pitlochry,

Perthshire, PH16 5LB

www.scotland.gov.uk/marinescotland

© CrOwn COPyrIgHT MArInE SCOTLAnd 2010

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ThehuntedPike are a unique component of Scotland’s fish fauna, and have a special place in angling folklore. Tales of monster pike abound and fire the imaginations of many anglers. Scottish waters have undoubtedly been capable of producing very large pike, reputedly in excess of 50lb (23 kg). It seems likely that such fish were provided with abundant large prey in the form of runs of sea trout and salmon. These fish put on much of their growth in mainly marine waters, and therefore import nutrients into the poorer freshwater systems. At present, mortality of salmonids at sea is high, and we may have to wait for a return to the days of high salmon returns and correspondingly large pike in some waters. There is evidence that waters stocked with trout may become the new source of giant pike, and careful management should ensure excellent angling opportunities for both the pike and their prey.

ManagementThere is no doubt that pike have the potential to reduce populations of prey fish, which may include commercially important species such as Atlantic salmon, Salmo salar L. As a consequence, managers of salmonid fish have on occasion attempted to control pike populations. There is a growing awareness that culling must be approached with caution because cannibalistic large pike may regulate numbers of smaller pike. If these large pike are removed, the resulting explosion in numbers of rapidly growing small pike can increase the damage to prey populations. Each management case should be considered individually.

OriginsThere has been much debate over the origins of Scottish pike. The fish have re-invaded Scottish waters following the last ice age, but it is not clear exactly how this occurred. undoubtedly there have been introductions by man. For example pike were used to ‘thin-out’ trout that had become too abundant and suffered stunted growth. Monks reputedly introduced pike into their stew ponds to provide weekly food fish. This is a surprising management tactic because pike production would have been low and at a cost of many lost prey fish, which, arguably, could have provided equally good food. Pike spawn in spring and deposit thousands of sticky eggs on water plants. It is possible that these eggs attach to birds and mammals, and then are dispersed to new waters. new genetic tools may allow a retrospective assessment of some of the geographic spread of pike.

Thefutureregardless of how they arrived, pike are here to stay, and they provide fascination and enjoyment to many people, especially those anglers who specialise in catching them. The most important consideration now must be that anglers do not contaminate the very waters that hold the secret to producing large pike by introducing non-native fish species brought along as bait. Introduced animals can destroy the balance of ecosystems, and once that balance is lost, it may never be recovered.