The freshwater fishes of the British Isles

Front matter

041 1*.

MIPl

®»,if in,

Preface

^TTSHES captured in the fresh waters of the British Isles are not for the most part of great commercial importance. The Salmonoids are a notable exception to this statement, for the Salmon and Trout are valued food-fishes, and the Windermere Char and the Lough Neagh Pollan are netted in numbers for the market. Smelt and Shad are also the objects of regular fisheries, and on the Severn Lampreys are still captured and potted, whilst the Eel fisheries are an important industry except in Scotland, where this fish is not appreciated. But the so-called coarse fishes, Pike, Perch, Roach, Bream, etc., are seldom exposed for sale in this country ; they are not inedible ; some, indeed, are very well flavoured, and are valued as food-fishes on the Continent. In former days in England, Pike, Carp, Tench, and other species were esteemed as luxuries, and every large country establishment had a pond wherein fish were kept and fattened for the table. But in those days transport was a very different affair, and so long as fresh sea-fish can be obtained

VI at a low price in inland markets, the coarse fishes of our lakes and rivers are not likely to rise in popular estimation.

However, there are few species that do not interest the disciple of Walton, who captures the larger fish for sport and the smaller ones for bait, and it is to a large extent for the angler that this book has been written, although it is not a book about angling. It is an attempt to present in popular form the distinctive characters of our fresh¬ water fishes, and to give a reliable account of the main features of their life-history.

I believe that it will be found that this work is more complete than any of its kind that has yet appeared, for the different forms of Char and Whitefish receive detailed treatment, and natural hybrids are also included. In these groups I have been able to examine much larger series of specimens than have hitherto been available, thanks to the kindness of a number of correspondents who have sent me Char, Fowan, Pollan, Cyprinoid hybrids, etc., and during the last few years I have described several new forms of considerable interest.

But much still remains to be done ; I am still uncertain as to the occurrence of Pollan in Corrib and Killarney ; I know that Char inhabit a number of lakes from which I have not been able to "et

o

PREFACE

« • Vll

them, and I am sure that a thorough study of the Cyprinoids, in a favourable locality like Lincolnshire or the Broads, would reveal the existence of many hybrids as yet undescribed. Moreover, growth, migrations, food, and habits offer a fine field for the student.

However, it cannot be denied that in recent years our knowledge of the fishes which live in our lakes and rivers, and of their life-history, has increased enormously, and the present time is, therefore, an appropriate one for summarizing and bringing together what is already known.

All the illustrations in this book have been drawn by myself, and it has been my aim to show the characteristic features of each species rather than to produce an artistic effect.

C. T. R.

Contents

TAGE

Introduction — Classification and Taxonomy . xv

CHAP.

Chapter I

Lampreys and Hag-fishes. The Lamprey family : the Sea Lamprey — specific characters — size — distribution — breeding — death follows breeding — structure and habits of larvae — metamorphosis — habits of adult — origin of name — value as food. The Lampern : differences from Sea Lamprey — distribu¬ tion — migrations — breeding — food and habits — uses — other names. Planer’s Lamprey : differences from Lampern — distribution — metamorphosis

''HE Lampreys ( Petromyzonidce ) and Hag-fishes

X (. Myxinidce ) differ widely in structure from the Selachians and true fishes, and in many respects are more generalized; they constitute a distinct class, the Cyclostomata or Marsipobranchii. They are naked eel-shaped animals without paired fins, and with the median fins supported by internal carti¬ laginous radials, but lacking dermal fin-rays ; the internal skeleton is cartilaginous, and there are no bones anywhere ; the terminal mouth has no jaws, but there is a very muscular protrusible tongue, which is armed with cuspidate horny laminae, and works like a piston, rasping off the flesh of the fishes on which these animals prey ; further characteristic peculiarities of the group are the presence of only a single median nasal opening and the structure of the gills, which are parallel vascular laminar ridges on the inner walls of a paired series of well-separated muscular pouches, communicating internally with the pharynx and opening either directly or by means of ducts to the exterior.

Water is often both taken into and expelled from the branchial sacs through their external apertures ; this is accomplished by the alternate expansion and contraction of their muscular walls, and the branchial skeleton, which is well developed only when the sacs are large, lies external to them, and is nearly rigid, serving to prevent the collapse of the branchial region ; this method of respiration is no doubt due to the parasitic habits of the Marsipobranchs, for when they are attached to other fishes they cannot take water through the mouth into the pharynx, and by contracting the latter expel it through the gill-openings, which is the normal method of respiration in other fishes.

The Hag-fishes are exclusively marine, and many of them occur in deep water ; they are in most respects more degenerate than the Lampreys ; they bore right into the fishes which they attack, and devour them until practically nothing is left but skin and bone.

The Lampreys are found on the coasts and in the rivers of all temperate regions ; there are about twenty species, most of which spend part of their life in the sea, whilst all appear to spawn in fresh water. In them the mouth is surrounded by an expanded circular lip or ‘ suctorial disc * which bears horny teeth ; at its inner edge, and placed above and below, are two cuspidate horny plates, which may be regarded as enlarged or coalesced teeth, and are termed the supra-oral and infra-oral laminae ; within the mouth are seen the laminae that arm the tongue, an anterior unpaired one and a posterior pair. The eyes are subcutaneous, but fairly conspicuous, and on top of the head, between or a little in advance of the eyes, appears the nasal opening ; the small gill-openings, seven in number on each side, form a series which begins not far behind the eye. The fins are two dorsals and a caudal ; the former are placed behind the middle of the length of the fish, and the latter is composed of a long lobe both above and below at the end of the tail.

With their suctorial disc the Lampreys attach themselves to fishes, which they devour, sucking the blood and scraping off the flesh by means of the toothed laminae on the tongue. Whilst there can be no doubt that in many respects they are a very primitive group, many of their peculiarities are due to their manner of life, and they may even have evolved from ancestors which had jaws. All have a remarkable life-history, as the larvae differ greatly from the adults in structure and habits, and undergo a fairly rapid transformation into the adult form after some years of larval life.

The British species are three in number, namely, the Sea Lamprey ( Petromyzon marinus ), the Lampern or River Lamprey ( Lampetra fluviatilis ), and Planer’s or the Brook Lamprey ( Lampetra planeri ). The larvee, known as Pride, Mud Lamprey, or Blind

Lamprey, have been described as a distinct genus and species under the name A mmocostes branchialis.

The Sea Lamprey (. Petromyzon mar inus) is dis¬ tinguished from the others by its dentition. The suck¬ ing disc is covered with conical teeth arranged in oblique radiating series, four inner teeth on each

Fig. i. — Suctorial discs of Sea Lamprey («) and Lampern (b). s. supra-oral lamina ; l. anterior lingual lamina ; i. infra-oral lamina.

side being enlarged and bicuspid ; the supra-oral lamina is narrow and bicuspid, the infra-oral lamina has seven to nine cusps, and the anterior lingual lamina bears two curved denticulated ridges separated by a median longitudinal groove. The first dorsal fin is separated from the second by an interspace, the second from the caudal only by a notch. The colour is grey, yellow, or green, marbled or spotted with olive, brown, or black.

The Sea Lamprey attains a length of more than

S

3 feet and a weight of over 5 lbs., its usual size being from 20 to 30 inches ; one of 20 inches is figured (PI. I, Fig. 1). It is found in the North Atlantic and Mediterranean, entering rivers in Europe and North America. It is generally dis¬ tributed in the British Isles, and appears to enter our southern rivers at an earlier date than those in the north, for in the Severn at Worcester the fishing season used to be from February to May, and the spawning was over in June, whereas in Scotland the Lampreys are said not to ascend until June, spawning in July or August.

By far the best accounts of the life-history of this species have been given by two American authors, Professors S. H. Gage and H. A. Surface, who have studied it in the lakes of the State of New York. Although structurally similar to the true Sea Lamprey, the Lampreys of this region are peculiar in that they never go down to the sea ; they spawn in June, leaving the lakes and seeking out the clear brooks, often stealing a ride by fastening on to large fishes bound in the same direction ; at this time the ground-colour changes from grey to bright yellow, and the two sexes become markedly different in appearance, the male developing a ridge along the middle of the back and a prominent anal papilla, and the female a so-called anal fin.

The Lampreys migrate independently, and a large majority of the earliest to enter the streams are males; the spawning-place is chosen where the stream is fairly rapid, usually just above a ripple, and where the bottom is sandy but strewn with pebbles. Here a space is cleared by moving the stones a little way down stream until a sandy ‘ nest ;

is formed, usually oval in form and slightly hollowed out, with a pile of stones just below it. If the male arrives unaccompanied he starts operations by himself, but on joining him the female helps; they fasten on to the stones with their suckers, and with powerful efforts loosen them and drag them down stream.

The female now secures herself by means of her sucker to some large stone near the upper end of the nest, and her mate attaches himself to her in the same way near her head, and winds himself partly round her ; then the two together stir up the sand with vigorous movements, whilst the eggs and milt are simultaneously deposited. The eggs are covered with an adhesive substance, and particles of sand stick to them, so that they sink to the bottom of the nest. The pair now separate and at once commence removing stones from above the nest and enlarging the pile at the lower end, the sand thus loosened being carried down and covering all the eggs. This process is repeated at short intervals until the spawning is completed, and then they leave, many Lampreys being found going down stream or attached to stones below the nesting-places. Accord¬ ing to Professor Surface, all die after spawning; the intestine has atrophied, they are emaciated, their skin is torn off in many places, they become stoneblind and covered with fungus, and are so com¬ pletely debilitated that recovery is out of the question.

The development of the eggs is rapid, and in from ten to fifteen days the larvae are hatched ; about a month later, at the end of July, when they are about half an inch long, they leave the nests, where they

Plate I

Sea-lamprey ; 2. Lampern have hitherto lived in the sand, and wander down stream until they find some suitable spot, often at a bend where the water runs slowly, where they burrow in the sand or mud.

The larvae, or Prides, as they are called in England, differ greatly from the adults ; they are toothless, with a small transverse lower lip and a hood-like upper lip, and the entrance to the mouth is guarded by a number of fringed barbels which form a very perfect sieve. The eyes are hidden and quite rudimentary, the small gill-openings lie in a groove, and the fins are low.

Each Pride forms a tube in the sand or mud in which it lies; the tube is usually open at the end, so that the water flows in freely. When disturbed the Prides worm their way through the sand and do not wriggle out if they can help it ; they feed on minute organisms. They probably live in this way for three or four years, and when they are from 4 to 6 inches long change into the adult form.

It may here be mentioned that the Prides of the different species of Lampreys are so similar that the name Ammoccetes branchialis is applicable to all. The name “Blind Lamprey” refers to their rudi¬ mentary eyes, and that of “ Mud Lamprey ” to their habit of remaining buried in the mud, whence they may be dug out in quantities in small brooks if the stream above be dammed up.

The metamorphosis takes place in the autumn ; first the eyes appear, and as they become more evident the mouth is contracted, the upper and lower lips join to form a single circular lip, and the fringed barbels become reduced to simple papillae surround¬ ing the mouth ; then the lips grow out to form the sucking-disc, the teeth develop, the branchial groove disappears, etc. Numerous important internal changes have accompanied those more easily observed, and the whole process occupies the greater part of two months, from about the end of August till the middle of October. Until the transformation is complete the Lampreys may still be captured in the sand, but they are more active than the larvae which are not changing, and attempt to swim away when disturbed. After the meta¬ morphosis the young Lampreys go down to the lakes, where they live on the fishes; sometimes a fish attacked has been observed to rise to the surface and turn over on one side, so that the head and gills of his enemy are out of the water and he is forced to drop off.

Two or three years elapse before the Lamprey attains sexual maturity and seeks the streams to end his career in perpetuating his race.

This account agrees with what we know of the Sea Lamprey in this country, except that the sea takes the place of the lakes as the home of the adult form, and, as might be expected, a larger size is reached. In the sea this species lives chiefly on Cod, Mackerel, etc., and it is on record that large numbers attached themselves to a Basking Shark, not leaving it until it was dead. Quite recently one was landed at Buckie, which had fixed itself to the rudder of a fishing-boat and could not be detached until the boat had been beached.

In their migrations the Lampreys are said to be often carried into rivers by Salmon, and have been described as ascending rapid streams by plunging quickly forward and hastily attaching themselves to some fixed object, such as a large stone, and then resting, waiting an opportunity for a new plunge ; in this connection it may be mentioned that the name Lamprey is derived from the mediaeval Latin Lampreda , a corruption of the older Lcimpetra , from lamb ere, to lick, and petra, a stone.

At one time Lampreys were much appreciated as a delicacy, so much so that there was a regular fishery in the Severn, which was, and still is, the most noted river for them, although they now appear to be scarcer than formerly. The city of Gloucester used to present the reigning monarch with a dish of Lampreys every Christmas, and the death of Henry I. was attributed to a too hearty meal of these fishes.

The Lampern or River Lamprey ( Lampctra fluviatilis) differs from the Sea Lamprey especially in the dentition (Fig. i). The disc is smaller, and has an outer series of small marginal teeth, within which is in front an irregular double row of conical teeth, and on each side three large teeth, the first and last of which are usually bicuspid, the middle one usually tricuspid. The supra-oral lamina is broad and has a pointed projection at each end, the infra-oral lamina has from six to nine more or less acutely pointed cusps, and the anterior lingual lamina bears a single transverse denticulated ridge with an enlarged median denticle. The first dorsal fin is separated by an interspace from the second, which is triangular in form and continuous with the caudal. The coloration is silvery white, with the back bluish or greenish.

This is a smaller species than the preceding ; the example figured (PI. I. Fig. 2) is a foot long, and the greatest length attained is not more than 16 inches; as compensation for this, the Lampern is much more abundant than the Sea Lamprey. It is found on the coasts and in the rivers of Europe, Siberia, Kamchatka, and Western North America from Alaska to California, and is plentiful enough in many British and Irish rivers, particularly the Severn, Trent, Ouse, Dee, etc.

Our knowledge of the life-history of this species is rather unsatisfactory, but it seems that a number of individuals reside permanently in fresh water, whilst the rest, like the Sea Lamprey, spend the greater part of their adult life in the sea and enter the rivers chiefly in order to spawn. The latter enter the rivers in the autumn or winter months, and later on make their way into the smaller streams, from April to June assembling in groups of thirty or forty on shallow fords where the bottom is gravelly ; their breeding habits are precisely similar to those of the Sea Lamprey, except that several couples share in making and using a nest. The larvrn cannot be distinguished from those of the Sea Lamprey, and undergo a similar metamorphosis; a considerable proportion of the young Lamperns make their way to the sea, but in some of our rivers, such as the Trent, and in lakes like Loch Lomond, a number of them remain and spend their whole life in fresh water.

Thus whilst the Sea Lamprey parallels the Salmon in that both are migratory species, living in the sea and ascending the rivers to spawn, and only

1 1

losing their migratory habits where large areas of fresh water offer abundance of food, as in some lakes of Eastern North America, the Lampern and the Trout resemble each other in that they are the smaller species, including both migratory and permanently fluviatile individuals in our waters. The Lamperns attach themselves to other fishes, sucking the blood and devouring them ; they are also said to feed on worms, insects, etc. In Loch Lomond they have been described as attacking and destroying the Trout and Powan ; the latter especially fall easy victims to their voracity, and may frequently be seen floating on the surface of the water with the Lamperns attached, their jaws and heads buried in the flesh of their victims. In the Baltic they follow the shoals of Herring in the summer-time, but enter the rivers in the autumn.

Lamperns may often be seen swimming like Eels against the stream, or holding on to stones at the bottom ; the Irish naturalist, Thompson, once observed, on a warm summer’s day, a number of Lamperns attached by their mouths to the under surface of the leaves of water-lilies in a pond near Belfast, the wriggling of their dangling bodies producing a strange effect.

The Lampern can live out of the water for days, and is thus easily transported alive in baskets ; it is said to be excellent food either stewed or potted, but its chief use in this country appears to be as a bait for Eels, Cod, Turbot, etc., its especial virtue being its toughness on the hook. For this purpose it used to be captured in large numbers in the Thames, and still is in the Trent, whence they are sent alive to Grimsby.

I 2

Other names for the Lampern are “ Stone-eel ” and “Nine-eyes,” the nasal aperture, eye, and seven gill-openings making up the count.

The Brook Lamprey or Planer’s Lamprey ( Lampetra planeri) differs from the Lampern in that the teeth are blunter and the edge of the suctorial disc is more strongly fringed, whilst the dorsal fins are contiguous or continuous, separated by a notch only, and the free edge of

Fig. 2. — i. Larval Lamprey or Pride ( Ammoccetes ). 2. Planer’s Lamprey.

the second dorsal is usually more distinctly rounded, instead of angular.

It is a smaller species, not growing to more than half the length of the Lampern, and has a different distribution, for whilst both species are found in Europe and Siberia, this one occurs also in Japan, but is absent from America. It is common in Britain to at least as far north as Perthshire, and is widely distributed in Ireland.

Planer’s Lamprey is usually found in the smaller streams, brooks, and ditches, and never goes down to the sea. It was in this species that the trans¬ formation of the larval Pride into the adult

Lamprey was first observed. Professor A. Muller, in 1856, described how he had watched Planer’s Lampreys spawning in a brook near Berlin and had seen the eggs hatch out in about three weeks and develop into Prides, previously known as Ammoccetcs branchialis. According to his further observations, the larvae live three or four years before they change into the adult form, the transformation occupying twenty-six days or more, and then they live only for a few months, dying after spawning. The breeding habits of this species are precisely similar to those of the Lampern, and the season for spawning is the same.

Chapter II The Sturgeon

The class Pisces : the subclass Chondrostei- — palaeozoic Chondrosteans — the Paddle-fishes. The Sturgeon family : the Sturgeon described — variation in number of scutes — only one British species — distribution — size — food and habits — only stragglers in our rivers — commercial importance — names

WITH the exception of the Lampreys all the

freshwater fishes of the British Isles belong

to the class Pisces. In this class the body is usually

covered with scales, which in the more generalized

types have the form of juxtaposed rhombic bony

plates, but in the more specialized ones are thin,

rounded, and imbricated. Median and paired fins

are present ; they are supported basally by an

internal skeleton, and are also provided on each side

with a series of dermal rays. The endoskeleton may

be cartilaginous or bony, but there are always a

number of external or membrane bones ; the mouth

is bordered by bony jaws ; the pectoral arch is usually

connected with the skull by a series of bones. The

gill-sacs of the Lampreys are represented by clefts

leading from the pharynx into the branchial chamber,

which opens behind to the exterior, and is covered by

the opercular membrane, supported by the opercular

bones and branchiostegal rays ; the interbranchial

septa, or walls of the clefts, are so reduced that the

THE STURGEON gill laminae project outwards as filaments, and the branchial skeleton, supporting the pharynx between the clefts, is movable ; water is taken in through the mouth, and by the contraction of the pharynx is sent through the gill-clefts and over the gills, and so out¬ wards via the gill-openings. The nasal sacs are paired and lateral ; each is usually provided with two external nostrils. An air-bladder is typically present.

Of four subclasses of the Pisces , two, the Crossopterygians and Dipnoans, are represented at the present day by only a few species in the fresh waters of tropical countries. The remaining two, the Chondrosteans and Teleosteans, include British fresh¬ water species.

The Sturgeons (A cipenseridce) and the Paddle-fishes ( Polyodon tides) are the specialized and in many ways the degenerate living members of a very ancient and generalized group of fishes. The essential characters of the subclass Chondrostei to which they belong are as follows : —

The bones overlying the primary pectoral arch and connecting it with the skull are four in number; the rays of the dorsal and anal fins are much more numerous than their endoskeletal supports, which they simply overlap ; the pelvic fins, like the dorsal and anal, have each a muscular basal lobe containing a well-developed series of radial segments of their skeletal rods ; the caudal fin is heterocercal, i.e. the axis of the tail is turned upwards, the upper (supra-caudal) lobe is reduced to a series of spines, and the lower (infra-caudal) lobe is strongly developed.

1 6

In the Chondrostean fishes found fossil in the palaeozoic rocks the mouth, head, and scaling were normal, but their modern descendants are very remarkable. The Paddle-fishes ( Polyodontidcz ) of China and the Mississippi have the body naked, the eyes very small, the snout much produced, and the mouth rather large and non-protractile ; there are no pnemaxillaries and no branchiostegal rays. The Sturgeons (Aczpenserzdd), with twenty or more species from the seas and rivers of Europe, Asia, and North America, differ from them especially in the presence of a transverse series of four barbels on the lower side of the snout, in front of the small, protractile mouth,

THE STURGEON

1 7 whilst there are five longitudinal rows of large bony scutes on the body, a mid-dorsal and paired lateral and ventral series ; the primitive scaling is retained on the upturned part of the tail ; another peculiarity is the presence on each side of a strong pectoral spine, formed by the fusion of the anterior fin-rays.

The Sturgeons are mostly anadromous fishes, living in the sea and entering rivers to spawn, but in some of the large lakes and rivers of North America they have become permanent residents. They are very variable, change greatly during growth, and also hybridize to a considerable extent, so that there has been considerable difference of opinion as to the number of species entitled to recognition ; it is generally agreed that there is only one species in Western Europe, but some authors are of opinion that a second species may occasionally cross the Atlantic from America and enter European rivers, a matter which is dealt with below.

The Sturgeon ( Acipenser sturio ) has the body elongate, subcylindrical anteriorly and tapering posteriorly. The size, shape, and arrangement of the bones which cover the upper surface of the head are subject to great variation ; thus the frontals may be in contact for the whole of their length, or may be completely separated by an ethmoidal plate. The snout is covered above with small bony plates and is rather long; in young specimens it measures at least half, and in examples of from 2 to 3 feet not much less than half of the length of the head, but in large fish only about one-third ; the insertion of the barbels is nearly equidistant from the mouth and the tip of the snout in young and half-grown

I 8 examples, but is nearer to the end of the snout in large fish. The dorsal fin is placed far back, and is composed of from thirty-seven to forty-six rays ; the anal, which begins below the middle of the dorsal and extends a little farther back than that fin, has twenty-four to twenty-nine rays, and the pelvic fins have the same number. There are from ten to sixteen scutes in the dorsal series between the head and the dorsal fin, and from nine to fourteen in each ventral series between the pectoral and pelvic fins ; the lateral series increases in number to some extent with age, owing to the addition of small scutes posteriorly; in 1870 Dr. Gunther counted the lateral scutes on a number of European examples, and found twenty-six to thirty-one in the young, but twenty-nine to thirty-four in half-grown and adult fish. A larger series or specimens would no doubt have shown greater varia¬ tion ; thus Day found only twenty-seven scutes on one side and twenty-eight on the other in an adult fish more than 5 feet long, from Margate, whilst in a specimen 18 inches long, from the Adriatic, I count thirty-four on one side and thirty-five on the othei and in one of 30 inches, from the Gironde, I count forty on each side, and after careful comparison I am convinced that these are true Acipenser sturio. It has been assumed that specimens with a large number of lateral scutes, as, for example, one said to be from the Tay, with thirty-eight on one side and forty on the other, belong to an American species (A. macn - losus), which has been supposed to cross the Atlantic occasionally ; probably they cannot be distinguished from American examples named Acipenser maculosus , but I am unable to separate these specifically from other American specimens with fewer scutes, named