A Report of Investigations Concerning Shad in the Rivers of Connecticut

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A REPORT OF INVESTIGATIONS

CONCERNING SHAD

IN THE RIVERS OF CONNECTICUT

PHILIP H. MITCHELL AND STAFF

TO THE STATE BOARD OF FISHERIES AND GAME

HARTFORD PUBLISHED BY THE STATE 1925 PUBLICATION

APPROVED BY

THE BOARD OF CONTROL STATE BOARD OF FISHERI S AND GAME

COMMISSIONER

FREDERIC C. WALCOTT, President WILLIAM K. MOLLAN KARL C. KULLE

JOHN W. TITCOMB, Super ntendent TABLE OF CONTENTS

A REPORT OF INVESTIGATIONS CONCERNING SHAD IN THE RIVERS OF CONNECTICUT

PART I Page Introduction ...... 7-9 Organization and staff ...... 9-10 Embryo and larval shad ...... 11 Biological examination of the Connecticut and its tributaries 12-22 Plankton Qualitative examination of samples from the Connecticut River 14-15 Qualitative examination of samples from the Farmington River ...... 16-17 Qualitative examination of samples from the Salmon River . 18-19 Quantitative plankton estimations on Connecticut River water 20 Quantitative plankton estimations on Farmington River water 20 Chemical examination of the Connecticut and tributaries ...... 22-27 Dissolved oxygen in water samples from the Connecticut River 23 Dissolved oxygen at a given point in the Farmington River as affected by the action of sunlight on plants ...... 26 Food of young shad ...... 28-35 Summary of observations on food of larval and young shad 31 Growth of young shad ...... 35 Measurements of the total lengths of young shad taken from ponds at Joshuatown ...... 36 Enemies and parasites of shad ...... 37 Artificial propagation of shad ...... 38-41 Shad caught and fry planted ...... 42-44 Summary ...... 44

PART II Age of shad (Alosa sapidissima Wilson) as determined by the scales. By Prof. N. Borodin ...... 46-51

PART III A confirmation of Borodin's scale method of age determination of Connecticut River shad. By R. L. Barney ...... 52-60

PART IV Report on helminth parasites from the shad. By Dr. Edwin Linton ...... 61-63 A REPORT OF INVESTIGATIONS CONCERNING SHAD IN THE RIVERS OF CONNECTICUT By PHILIP H. MITCHELL AND STAFF.

PARTS I—TV

PART I. The story of the decline. of Connecticut River shad is much like that of many other species of fish and game. In earlier times, shad came in great schools into all the rivers of the state, especially into the Housatonic, the Connecticut and the Thames and their tributaries. In the Connecticut River system, they made their way far to the north and were caught in large numbers by fishermen of New Hampshire, Vermont and Massachusetts as well as Connecticut. As late as the eighteen seventies, shad were so abundant during the season that they were sold at ten cents apiece and even then could not all be disposed of while fresh but were salted down during certain years as they were every year during colonial times. But the relentless progress of civilization began to exert its effects even in the nineteenth century. One after another, dams were built on the main rivers and their tributaries. All fishways constructed at various dams failed to permit shad to pass them and so the river areas visited by the fish became more and more restricted. The shad are anadromous. They migrate annually from salt water to fresh water streams in order to perform their spawning function. They return to salt water soon after they have spawned. The females, "roes", and the males "bucks", give out their ripe eggs and milt into fairly swift- running water over sandy or gravelly bottoms and fertilization of the eggs depends upon chance meetings with sperm in the water. Their spawning habits thus make successful reproduction dependent upon access to suitable spawning places. Dams greatly cut down the number of the localities at which shad could reproduce. Other changes followed in the wake of progress: Forests were decreased in area thus altering the water retention of the soil. Dams held back the river water and so probably caused a tendency to higher temperatures in the rivers.

7 Dredging and breakwater construction at the mouths of rivers had various effects on the direction of the streams of fresh water flowing into Long Island Sound. What effects these changes may have had on the tendency of shad to find their way into Connecticut rivers is unknown but they may have operated to decrease the abundance of the annual shad runs. With increase of population came increased output of sewage and trade wastes into the rivers of the state. Grad- ually sludge collected on river bottoms in the deeper places. These are just the locations which the young shad haunt and where they find their food. Also in these deeper spots, fertilized shad eggs, being nonmotile and heavier than water, tend to collect and hatch out. Sludge and soft mud envelope the eggs and smother them before they hatch. Such material also depletes oxygen of the water by causing fermentation. This cuts down the abundance of the small animal forms which young shad feed on and thus decreases their chances for successful growth. They remain for a time in the rivers where they are hatched in the spring and early summer and should grow to a length of three or four inches before they migrate to salt water during October and November. Sewage or any other pollution, even when not sufficient to actually kill adult shad or even the little ones, may indirectly cause serious limitationS of the success of propogation of the species. Every year, however, shad fishing goes on: The numbers taken during the annual runs probably do not decrease in proportion to the decline of natural opportunities for reproduction. This constitutes overfishing, so far as maintenance of the species is concerned, even though the total number of shad caught during successive years does noticeably decrease. Only when the difference between the death rate from all causes and the birth rate under natural reproduction is made up by artificial propagation can a continuation of the species be expected. There have been a number of years when artificial propagation in Connecticut has either been at a standstill or has obviously been too small in amount to compensate for overfishing. In addition to the unfavorable conditions arising in the rivers, other circumstances may have depleted shad. While in salt water they are the prey of many of the large and predacious fishes. Shad, like all fish, are more or less subject to diseases. Information on both of these matters is meagre and scattered, so that the extent to which shad may have become depleted in salt water can only be conjectured. For these various reasons and possibly others, the decline of shad abundance might well be expected. It is of course no more surprising than the depletion of salmon or of any species of wild life sought by man. Although reports for several of the years between 1870 and 1880 show a great abundance of shad in several of our rivers, and especially in the Connecticut itself, the decline was so rapid during the next two decades that the catch reported for 1892 was less than 19,000 fish. A few years later shad are reported as more abundant. The recorded catches in Connecticut during the ten years 1897-1906 averaged 114,890 shad per year with the maximum, 176,085 for the season of 1903. During the next decade, 1907-1916, the reported annual catches averaged only 44,300 shad, or about one-third of the average catch during the preceding decade. From 1917 to 1920 some improvement in the abundance of shad was reported; but in 1922 and 1923 new low records were made. During these two years the smallest catches of shad (13,821 and 13,350) ever reported for Connecticut were recorded. These figures could readily be taken as an index of approaching extinction. The outlook seemed especially discouraging, because, along with decrease of the shad catch, there was a marked failure of opportunity to obtain spawn for artificial propagation. In view of this situation the State Board of Fisheries and Game recommended in 1922 "that a study of the life history of the shad in fresh waters be made with a view to determining whether the restoration of the fishing under present day conditions is possible." An appropriation was made for this purpose by the Connecticut legislature.

Organization and Staff As a preliminary to planning for these studies, a conference was called in Hartford on April 28, 1923, for the purpose of considering all phases of the shad problem. . The conference was attended by : Professor S. C. Prescott, Mass. Institute of Technology Professor J. W. M. Bunker, Mass. Institute of Technology Professor G. A. Baitsell, Yale University Professor F. P. Gorham, Brown University Professor P. H. Mitchell, Brown University Professor H. B. Goodrich, Wesleyan University Mr. A. H. Leim, University of Toronto Mr. H. F. Taylor, U. S. Bureau of Fisheries Dr. EmTrieline Moore, N. Y. State Conservation Commission Hon. F. C. Walcott, President of this Board Mr. J. W. Titcomb, Superintendent of Fisheries and Game.

9 Mr. Walcott presided. An account of the work done on shad investigation for the Biological Board of Canada was given by Mr. Leim, who freely gave the benefit of his two years' experience in this kind of work and made valuable suggestions concerning the proposed undertaking in Con- necticut. Mr. Leim has since been in correspondence with the staff conducting this investigation and his continued helpfulness is gratefully acknowledged. A description of shad investigations carried on for the U. S. Bureau of Fisheries was then given by Mr. Taylor, who also made helpful suggestions concerning the work to be done. Mr. Taylor and the staff of the Bureau of Fisheries have been very co-operative in putting their information at our disposal and in furnishing material for some of the work. After these two reports of investigations, there followed a general discussion of the nature of the problem and specific measures for its solution. Thanks are due to the par- ticipants' for their valuable counsel and for generously giving their time. Shortly after the conference the staff was organized for the investigation. Philip H. Mitchell, Professor of Physi- ology, in Brown University, was appointed Director ; Dr. Emmeline Moore, of the New York State Conservation Com- mission, was the Biologist of the staff during such time as she was able to join in the work. Nicholas Borodin, formerly of the University of Petrograd, was the Icthyol- ogist for the investigation. Scientific assistants were employed from time to time for special parts of the work. Frank B. Littlefield did much of the chemical work. Henry E. Gallup assisted in biological investigations. John E. Blair did the bacteriological work, and many of the plankton counts. Raymond L. Barney investigated age determination by the use of otoliths. .Dr. Edwin Linton kindly aided the investigation by furnishing identifications and descriptions of shad parasites. The reports of the determination of the age of shad by Dr. Borodin, of the study of otoliths by Mr. Barney, and of examination of parasites by Dr. Linton, are appended.

1. They and the institutions which they represented, and other institutions, have cooperated in the investigation. We gratefully acknowledge our indebtedness to the biological laboratories of Brown University and the Massachusetts Institute of Tech- nology for the loan of certain instruments of precision, to the laboratories of Wes- leyan University for the use of working space, and for many favors, to the biological laboratories of Yale University and the United States National Museum, for aid in the identification of the species of certain specimens. We especially desire to express our appreciation of the cooperation of the New York State Conservation Commission in allowing us to have the services of their investigator, Dr. Moore.

10 Fig. 1.' Fig. 2.

Fig. 3. Fig. 4.

Fig 5. Fig. 6.

Fig. 1. Shad egg showing blastodisk in 4-celled stage, 2 hours after fertilization, 16. Fig. 2. Side view of blastodisk in 4-celled stage. Fig. 3. Early stage in embryo development following 4-celled stage. Fig. 4. Embryo in later stage showing segments or myotomes of the dorsal region. 38 hours after fertilization. Fig. 5. Embryo with outline well defined. About 2 days old. Fig. 6. Embryo just before hatching. Fig. 7.

Fig. 8.

Fig. 7. Shad larva shortly after hatching. Length about 10 mm. Fig. 8. Shad larva 5 days after hatching. Yolk sac absorbed. Food in the intestine shown by dark line. EMBRYO AND LARVAL SHAD. A working familiarity with the egg and larval stages of developing shad is required for making observations on the success or failure of their natural reproduction. Studies of the embryology of shad were published by Ryder in 1882 and 1885. These reports were accompanied by drawings representing the eggs and the larvae in various stages. A more extended series of illustrations, showing the stages of development at frequent intervals, seemed desirable. Figures 1 to 6 are micro-photographs of the egg from the time of fertilization until ready to hatch. Material for these photographs was taken from the hatching jars in the State Shad Hatchery at Windsor. The figures are accompanied by explanations of the time and condition of development. The rate of hatching is so markedly increased by rise of temperature, that a given stage of development of the embryo cannot be labeled as representative of a certain time after fertilization, unless a constant known temperature has been maintained throughout the process. The river water flowing through the hatching jars during these observations became warmer during each day, and cooler at night. Water temperatures were taken three or more times daily, but fluctuated so much that only a rough correlation between average temperatures and rate of development can be given. Muscular movements of the embryo, shown by occasional rapid, whip-like twitchings of the body within the egg-case, appear when development is a little more than half com- pleted. By this time the eyes are prominently developed and show a noticeable pigmentation. Pigmentation of the body is just beginning. Five to nine days, depending on the temperature, are required for hatchings. Muscular movements of the embryo become strong enough to break the external membrane of the egg so that the embryo becomes a free-swimming larval fish. It has the yolk sac attached to it. Figures 7 and 8 show the larvae in newly hatched stages. During about three days the yolk sac is the only source of nourishment and gradually diminishes in size as its contents are absorbed. After this the larval fish must find food.

11 BIOLOGICAL EXAMINATION OF THE CONNECTICUT AND ITS TRIBUTARIES.

The fitness of water for supporting fish life can be judged in various ways, but a study of the abundance of all plant and animal life gives information of especial value. Micros- copic life, the plankton, furnishes the food directly or indirectly for most other life in anaquatic environment. It is thus an excellent measure of the relative value of any water for support of fish life. The plankton of the Connecticut south of Windsor Locks and of the Farmington and Salmon Rivers was studied during this investigation. These waters are the chief ones visited by Connecticut shad. A third branch of the Con- necticut, the Scantic River, was also studied slightly, but is visited by so small a run of shad that its condition has little bearing on the shad problem. The water of ponds used for retaining young shad was also examined. Qualitative examinations, that is,—microscopic identification of sedimented or centrifuged samples of river water and of sifted samples of mud from river bottoms, were made at various localities through the summer months. Results of these examinations are tabulated below. They show that in the Connecticut and its chief shad tributaries, microscopic life is varied and includes crustacea and other microscopic animal forms fed upon by young shad. The results also indicate a satisfactory condition of both plant and animal forms in these rivers ; in that the organisms found include those which do not flourish in waters polluted so as to be unfit for fish life while typical pollution forms predominate only in certain locations of the Connecticut. These will be discussed in a later section. Quantitative estimations of the richness of the plankton of these rivers were also made. The Sedgwick-Rafter method was used. In general, the water samples were con- centrated by the use of an electric centrifuge but in some cases by filtration. Results, given as total numbers of organism per cc. and as Sedgwich-Rafter Standard units per cc. are reported below. In every case the water sample was put through silk bolting cloth to remove coarser particles (the net plankton) before concentration for plankton counting. The figures given thus refer to the smaller organisms

12 (nanno plankton) only. The net plankton was examined in most cases, but usually in a qualitative way. The samples examined quantitatively were, most of them, taken from the Farmington and Connecticut Rivers. A few samples were from the Scantic and Salmon Rivers and from the ponds used for retaining young shad at Joshuatown. It seemed better, however, to depend on other observations in the latter cases because warm weather transportation of water samples over the considerable distances between these localities and the laboratory at Windsor resulted in the death and disintegration of some organisms, and so tended to make the counting unrepresentative. The tabulated results of the counts show that the Con- necticut River is fairly rich in microscopic plants and animals and compares favorably with the water of large rivers in general. The Farmington River yielded small counts during the summer months. At this season the river is low and .opportunity for multiplication of microscopic life is poor because of rapids in the river. Sessile and bottom forms are abundant in the quieter pools and deep holes of the river, but the floating microscopic life is meagre, as in all small, rapid rivers at low water. The counts obtained on the Farmington River water and on the waters of the Salmon and Scantic Rivers compare favorably with those recorded by other observers on similar small rivers. At flood time in the spring (May, 1924) the plankton count of the Farmington is high. This is due to the washing-out of microscopic life from swamps and ponds overflowing into the river and its tributaries. Increase of plankton at freshet time is commonly observed in small rivers. Altogether, these quantitative observations tend to confirm the conclusions drawn from qualitative biological observations and from chemical examinations. The general con- clusion is, that these waters show no signs of serious pollution except in certain parts of the Connecticut to be described later. The balance between the plant and the animal plankton was found to be such as to clearly prove the absence of disastrous pollution by .either trade wastes or sewage. The fair abundance of ,Chlorophyceae and the general scarcity of certain typical Cyanophyceae was disclosed by these countings, and is a further indication that these waters are favorable to fish life in most of the localities examined. Rooted aquatic plants were found to grow luxuriantly in the Farmington and Salmon Rivers and in many parts of the Connecticut. In most localities grass-like forms (Valli- sneria) predominated but Elodea and many other rooted

13 QUALITATIVE EXAMINATION OF SAMPLES FROM THE CONNECTICUT RIVER

1923 1924 July August May June 12 24 24 2 6 13 14 15 20 23 24 27 26 26 3

Diatomaceae ...... Amphora ...... P PPPPPP • P•••• - Asterionella ...... P PPPPPP- 1) - PPP 1) Cocconeis ...... PPPP••PPP - •••• - Diatonta ...... p P PPP P Epithemia ...... P PP PPP P Fragilaria ...... PPPPPPPP- PPP•• P Melosira ...... P PP• PPPPPP • Meridion ...... P P Navicula ...... PPPPPPPPP PPPP P Surireila ...... Synedra ...... PPPPPPPPP •••PPP 13 Stephanodiscus . . . p . . . . Tabellaria ...... P P PPP P Nitzschia ...... PPPPPP

Chlorophyceae Mougeotia ...... P PPPPPP PP •••• - Spirogyra ...... p p P P P P • Ulothrix ...... p p . Sphaerozosma ...... P Cosmarium ...... P PPPP P Staurastrum...... PPPPPPPPP—P• Zygnema ...... PP P 1) Ciosterium ...... PPP •• P P13 ••• Pediastrum ...... PPPPPPPPP 13 - Tribonema ...... P Hydrodyction ...... p p p .. Tetraspora ...... P Micrasterias ...... P . .. Scenedesmus ...... PPPPPPPPP • PPP Ankistrodesmus ...... PPPPPPP P Clarophora ...... P PPPP P Drapernaldia ...... P P P Hyalotheca ...... P P P Batrachospernium ...... P P Sphaerocystis...... PPPPPPPP • PP 13

14 QUALITATIVE EXAMINATION OF SAMPLES FROM THE CONNECTICUT RIVER ( Continued)

1923 1924 July August May June 12 24 24 2 6 13 14 15 20 23 24 27 26 26 3

Protococcus PPPPPPPPPPPPP P Volvoxaceae. PPPPPPPPPPPPP- P Desmids, sp. PPPPPPPPPPPPPP P

Cyanophyceae Oscillatoria. P PP • • PPPPP• P Anabaena P P PPPP• - P — Lyngbya p Chroococcu - PP PPPPP • P Microcysti

Protozoa Dinobryon - PPP PPP P Cadonella Euglena p Diflugia Vorticella PPPPPPPPP Glenodinium . Paramoecium PPP P • PPP PP Rotifera PPPPPPPPPPPP P P

Crustacea Cyclops p p p Sida Chydorus . . Cypris . • PPP Daphnia p p p Bosmina ' Canthocamptus p p p Gammarus Polyphemu • Insect larvae . ppp Mites p p p . Bryozoa p p Mussel glochidia PP PP P

Many of these samples were not taken from the bottom and were therefore not examined for crustacea and insect larvae.

15 QUALITATIVE EXAMINATION OF SAMPLES FROM THE FARMINGTON RIVER

1923 1924 June July Aug. May July 77 8 12 13 18 25 2 24 9 20 20 22 3 3 3 14

Diatomaceae Asterionella ...... Melosira ...... P •• PPPPPP • PP 13 P•• — Navicula ...... PP PPPPPPPPP P PPP • Tabellaria ...... P P PPPPP••PP 1) 13 P Diatoma ...... - PPP P••PP P P P Surirella ...... Synedra ...... PPPPPPP P P P Fragilaria ...... PPPPPPPPPPPP P P Epithemia ...... Meridion ...... Amphora ...... P PP P

Chlorophyceae Closterium ...... P PP PP • PP Cosmarium ...... PPP 1) • P Xanthidium ...... Mougeotia ...... PP PPPP PP P P 13 • P Spirogyra ...... PPPPPPPP—PPP p p Sphaerozosma ...... Ulothrix ...... P PP PP P • Staurastrum ...... • P PP P 1) • Zygnema ...... Pediastrium ...... P PPPPP P Chaetophora ...... PPPP • 13 PP • Tetraspora ...... PPP- PPPP • P Scenedesmus ...... PPPPPPPP P P Cladophora ...... PPPP PP P Drapernaldia ...... P P P Hyalotheca ...... P P P Batrachospermum, pppppp . Protococcu ...... P PP PPP P P P Volvox ...... P - Desmids, sp...... PP PP - PPP P P

16 QUALITATIVE EXAMINATION OF SAMPLES FROM THE FARMINGTON RIVER (Continued)

1923 1924 June July Aug . May July 7 7 8 12 13 18 25 2 24 9 20 20 22 3 3 3 14

Cyanophyceae Oscillatoria ...... P P P P P P - Phormidium ...... Microcystis ...... P p Lyngbya ...... p .

Protozoa Dinobryon ...... P P p p p . Euglena ...... Vorticella ...... P P P Halteria ...... p . . Paramoecium ...... P PP • 13 13 Rhizopoda ...... Epistylis ...... Mastigoptora ...... P P ID • P •

Rotifera ...... PP • I) 13 P P PP•

Crustacea Cyclops PPP PP PPPPP 13 • I) • Chydorus ...... p p p p Cypris ...... P PP • P PP p• P - Daphnia . . . . . p . P P . Bosmina ...... • 13 13 P • 13 - I) • Canthocamptus ...... Gammarus ......

Miscellaneous Insect larvae PPPPPPPPPPPP P PPPP Sponge spicules ...... p p Mussel glochidia ...... PPPP P PP P P P Bryozoa ......

* These samples examined only for larger forms. Gammarus and other species of small crayfish were abundant and insect larvae were to be found in all samples, but in many of them only the microscopic life was examined so that the relative abundance of larger forms is not fairly indicated by this table.

2 QUALITATIVE EXAMINATION OF SAMPLES FROM THE SALMON RIVER

1923 1924 June July Aug. July 12 13 21 21 22 22 23 20 14 2 2

Diatomaceae Amphora Asterionella Cocconeis p P - • Diatoma p p . p Epithemia P . .. . F'ragilaria PloPP• PP P P PP Melosira • - 1) P Navictila PPPP P P P Surirella P P P Synedra p p p . p p Tabellaria PPPP Gomphonema p Pleurosigma P

Chlorophyceae Mougeotia P PPPPP P P PP Spirogyra PPPPPPP P P PP Ulothrix • P P .. Sphaerozosma . . P Cosmarium P P Zygnema PPPPP P P PP Closterium P P P Pediastrium P P Chaetophora PPPP 1) II ydrodyct ion P Oedogonium P P P Cladophora P Drapernaldia P PPPP P Micrasterias P Batrachospermum P P P P Protococcu PPP P P P • Desmids, sp P P P P P P P

18 QUALITATIVE EXAMINATION OF SAMPLES FROM THE SALMON RIVER (Continued)

1923 1924 June July Aug. July 12 13 21 21 22 22 23 20 14 2 2

Cyanophyceae Rivularia P P • Oscillatoria • - P P Phormidium P . Microcystis Anabaena

Protozoa Dinobryon P P P - P Vorticella P P P P Hydra Paramoecium P Heliozoa P Mastigophora p p p p .

Rotifera P P P P P

Crustacea Cyclops PPPPPP P pp Chydorus p . p p Sid a Cypris PPPPP Daphnia p p p Bosmina P P P P P P Gammarus P Polyphemus p P

Miscellaneous Water mite . Insect larvae PPPPPPP P P P Bryozoa p Mussel glochidia p . p . p p . .

* Incompletely examined.

QUANTITATIVE PLANKTON ESTIMATIONS ON CONNECTICUT RIVER WATER.

Standard Organisms Units Date Place per C C per C C

1923 July 12—North of mouth of Farmington River 747 674 " 24—At the mouth of Farmington River 163 142 " 24—At the mouth of Farmington River 261 189 Aug. 2—Rocky Hill Ferry 666 421 " 6—Middle Haddam ,.628 504 " 13—Rocky Hill, above Ferry 801 554 " 14—Cromwell 695 525 " 15—Bodkin Rock, below Middletown 732 665 " 20—Glastonbury, near Keeney Cove 592 510 1924 May 26—Windsor Locks 531 566 June 3—Windsor Locks 131 244

QUANTITATIVE PLANKTON ESTIMATIONS ON FARMINGTON RIVER WATER.

Standard Organisms Units Date Place per C C Per C C

1923 June 13—Shad Hatchery, Windsor 96 144 " 19—Shad Hatchery, Windsor 70 98 July 6—Shad Hatchery, Windsor 64 105 " 16—Near Rainbow Park 143 129 " 16—Mud Seine, Poquonock 89 111 " 16—Shad Hatchery, Windsor 151 141 " 17—Shad Hatchery, Windsor 139 109 Aug. 9—Loomis Institute, Windsor 135 86 1924 May 23—Mud Seine. Poquonock 409 704 " 24—Shad Hatchery, Windsor 529 888 " 24—Rainbow 444 698 June 18—Shad Hatchery, Windsor 305 504 " 30—Loomis Institute 403 246

20 plants including Potamogetons were also abundant, especially in the Salmon River along quiet reaches in the lower part. All rooted aquatic plants appeared to be in healthy condition. Filamentous algae were found in all parts of the rivers, but were especially abundant in the Salmon River, where they formed a thick carpet on some parts of the bottom. Varieties of Spyrogyra and Mougeotia were most frequent and abundant, but many other forms were found, as recorded above in the tabulated results of qualitative observations. Animal life of microscopic size was abundant in all localities. Several species of small cray-fish abound in the Con- necticut, Salmon and Farmington Rivers. Frogs and tad- poles are common. Of fish life, eels, pickerel, perch, suckers, horned-pout, bass, sunfish, sticklebacks, shiners and many species of minnows are frequently found. Large numbers of the young of all these fishes were taken in minnow seines at many localities of the three rivers under observation. All species of young fish were found in healthy condition and well supplied with food. Young alewives were obtained in quantity at Keeney Cove and at several localities on the Con- necticut. They also appeared to be thriving. It was noticeable that the species which can thrive in waters with muddy bottoms, species such as suckers, horned-pout and eels, were more numerous than the typically clean-water fishes. This is, perhaps, to be expected, because muddy bottoms are frequently found along the Connecticut and its lower tributaries. At certain points in the Connecticut River the effects of the sewage of the cities of Hartford and Middletown are evident in the character of the flora and fauna of the water. One of the places is the deeper part of the river south of the Rocky Hill ferry. Here a heavy sludge has settled to the bottom and the water is rich in those forms of blue-green algae (cyanophyceae) which thrive in oxygen-poor water. Oscilatoria is very abundant and spirulina is common. The sulphur bacteria (Beggiatoa), which are very apt to be present in polluted areas, are especially abundant here. The types of protozoa which inhabit polluted water are also abundant and sludge worms (Tubifex) are very common. Chemical examination of the water at this point confirms the biological examination by showing low oxygen content of the water. Other locations in the Connecticut showing similar effects of pollution are the deeper areas at and just below Middletown. The waters of the Connecticut do not entirely complete the process of self-purification, after the effects of Hartford sewage, before reaching Middletown and

21 here, the additional wastes of this city and the badly polluted waters of the Sebethe River have a cumulative action, so that the worst effects of pollution are registered here. Again, the deep holes are the bad places. Sludge settles, fermentation sets in and pollutional forms abound. Condi- tions comparable to those of a cess-pool are found. The small, free-floating, plant and animal life is typical of foul water. Beggiatoa, Oscillatoria, Sphaerotilus and Melosira, are the most abundant of the foul water plants. The Euglenidae are conspicuous among microscopic animals. The sludge of these "cess-pools" is threaded heavily with Tub- if ex and other sewage-inhabiting forms. Protozoa of the Pleuromonas type and bacteria abound in the more recently settled sewage matter. Spirochaetes, probably of fecal origin, are abundant. Aside from the deep holes at Rocky Hill and near Middle- town, the general biological conditions of these rivers indicate that the waters are suitable for fish life. Migrations of fish past these foul places are possible in the present condition of the Connecticut, because pollution has not yet rendered the entire stream unfit for fish ; but has seriously affected only the deeper holes where sludge collects.

CHEMICAL EXAMINATION OF THE CONNECTICUT AND TRIBUTARIES. In addition to biological studies, chemical examination of water may be used to obtain indications of its fitness to sustain fish life. Measurements of the amount of dissolved oxygen are especially useful, because all forms of ordinary pollution deplete oxygen in the water by causing oxidative bacterial putrefaction and other fermentations. Depletion of dissolved oxygen is destructive to fishes because they cannot attain a sufficient oxygenation of the blood to sustain their normal rate of physiological oxidation unless dissolved oxygen in the water is present in adequate concentration. The low limit of tolerance for fishes varies with the temperature of the water. At lower temperatures oxygen require- ments are less than at higher ones. The tolerance also varies with the different species of fish, some being able to withstand lower concentrations of oxygen than others. No hard and fast rules as to the exact limit can be drawn, but it is generally conceded that many species of fish cannot live in water containing dissolved oxygen in amount equal to or less than 30% of saturation, and that many species tend to avoid water which is less than 50% saturated with oxygen, or may show signs of distress if confined in such water.

22 Numerous samples of water collected during all of the summer months of 1923 and 1924 and taken under varying conditions of weather and at different depths, were analyzed for their content of dissolved oxygen. The localities from which samples were taken were along the Connecticut River from Windsor Locks to Essex, the Farmington from its mouth up to Tariffville, the Salmon from its mouth up to Leesville, the Scantic at points near Hazardsville and various ponds used for retaining young shad. The analyses were made by the Winkler titration method. The results were computed as oxygen in parts per million of water ; and also, as per cent of saturation with oxygen, at the temperature recorded for each sample. For the Farmington River, nearly all of the 110 samples analyzed had from 70 to 94 per cent of saturation. Only three samples were lower than 70 per cent of saturation, and two of these were above 60 per cent. One sample taken at the mouth of the Windsor sewer had 35 per cent of saturation. With the exception of this sample the oxygen values ranged between 6 and 10 parts per million. This one low sample is not representative, because others taken near the locality where it was collected were much higher in oxygen content. The measurements of dissolved oxygen thus confirm the biological examination of the Farmington River water and clearly indicate that pollution is not present in menacing amounts.

DISSOLVED OXYGEN IN WATER SAMPLES FROM THE CONNECTICUT RIVER.

Results are in per cent of saturation.

tA bi Location a X al X a a X 0 0 0 0 0 0 0 0

1. Windsor Locks at bridge 8-14 61 2. Windsor Locks below bridge 5-26 93 8-14 65 3. Windsor Locks at mouth of Farmington ------8-23 85 8-14 71 4. Windsor near mouth of Farmington ------8-14 73 8-23 70 5. Station 11, west shore - - 8-14 81 6. Station 11, midstream - - - 7-18 54 8— 4 50 8-23 7. Station 11, east shore - - - 8-14 52 8. 1 mile north of Hartford, west shore ...... 8-14 83

23 ti 4, aS Location 03 X CO X 04 04 C C 0 '8 0 0 0

9. Midstream, 1 mile north of Hartford ...... 8-14 83 10. West bank, Hartford at bridge ...... 8-14 69 11. Midstream, Hartford at bridge ...... 6-19 82 8-14 50 8-18 81 12. East bank, Hartford at bridge 8-18 61 8-27 54 13. Opposite Glastonbury - - 7-28 69 8- 9 71 8-18 56 8-20 49 14. Midstream, near Glaston- bury ------7-18 76 8- 9 66 8-18 50 8-20 55 15. Mouth of Keeney Cove - - 7-28 69 8-- 9 65 8-18 65 8-20 56 16. South of Glastonbury ...... 8-18 51 17. Rocky Hill ------8-18 34 8-27 34 18. Midstream, near Rocky Hill 8- 2 15 8-13 73 8-18 68 8-27 56 19. South Glastonbury - - - - - 8-13 69 8-18 50 8-27 34 20. North Gildersleeve Island.... 8-27 63 21. South of Gildersleeve Island 8- 3 68 8-28 38 22. Midstream, near Cromwell 8- 3 70 8-28 61 23. Portland ...... 8- 3 77 8-28 42 24. Near mouth of Sebethe River ...... 8-19 41 8-21 36 8-25 41 8-28 63 25. East of Willow Island ...... 8- 3 74 8-25 54 26. Middletown, near docks ...... 8-19 41 27. Middletown, midstream ...... 8-15 63 8-17 67 8-19 46 28. Midstream, below Middle- town ...... 8-15 59 7-13 56 29. Near South bank, below Middletown ...... 8-21 30 30. State Hospital dock_ 8-22 36 31. Midstream, near State Hospital dock ...... 7-13 57 8-22 52 32. Opposite State Hospital dock ------8-22 23 8-22 46 33. Below State Hospital ...... 8-22 55 34. Higganum ...... 8- 6 65 8-20 68 8-22 66 8-30 61 35. Opposite East Haddam - - 8-15 46 36. Midstream, near East Haddam ...... 8-15 49 37.. East Haddam ...... 8-15 51 38. South of East Haddam ...... 8-22 68 39. Below East Haddam ...... 6-17 89 8-22 68 8-30 73 40. Hadlyme ...... 6-17 89 8-16 64 8-30 72 41. Deep River ...... 8-30 72

24 In the Connecticut River, dissolved oxygen was fairly high in most localities, but showed low values in the polluted areas described in connection with biological examinations. The results of the measurements are collected in the accompanying table. A graphic representation of the average, minimum and maximum results, is given in Figure 9. In these curves the abscisae are distances in miles from Wind- sor Locks, and the ordinates are dissolved oxygen in per- centages of saturation. This chart brings out the fact that oxygen tends to low values in the water from Glastonbury to Higganum, but is especially low at South Glastonbury (near Rocky Hill) and at Middletown. Below Higganum, the dissolved oxygen is about the same in concentration as above Hartford and indicates that the river has effected a fair degree of self-purification. In no part of the river was the water found to be so depleted of oxygen that samples taken from every part of a given cross-section of the stream were low in oxygen. This signifies that fish could find their way past oxygen-low, foul places by following channels of better water. Only the deeper parts or holes where sedi- ment collects are low in oxygen content. The abundance of the green plant life in many parts of these rivers has a marked effect on the oxygen content of the water in summer time. This is the result of photosynthesis by green plants which liberate oxygen into the water while using carbon dioxide. This was especially noticeable in the Farmington River at Windsor. During the daytime, especially if sunny, the dissolved oxygen rose during the morning hours, reached a maximum in the afternoon and fell during the night. The accompanying table shows the effect of bright sunlight, as contrasted with cloudy conditions, in raising the oxygen content of the water. Corriespondingly, the hydrogen ion concentration which is chiefly determined by the relative abundance of carbon dioxide, fell with rise in oxygen. These effects are due, in the main, to the abundance of rooted aquatic plants. Floating green plants are not present in sufficient quantities in the Farmington River to cause these effects by photosynthesis. The significance of these effects lies in the fact that rooted aquatics are common or abundant in nearly all parts of the Connecticut and its tributaries where shad are found. Such plants are not only an index of the absence of disastrous pollution, but are useful in counteracting the effects of such pollution as is present. In addition to measurements of dissolved oxygen, the hydrogen ion concentration of the water in the rivers and in

25 shad-retaining ponds was determined. The colorimetric method employing Clark and Lubs indicators, was used. The hydrogen ion concentration shows whether the water is neutral, acid or alkaline. This information is useful because river and pond waters, ordinarily neutral or faintly alkaline, are rendered acid by the wastes from factories using acids and also by the carbon dioxide, hydrogen sul- phide and other acid substances which are produced by fermentations of sewage or other organic matter. Measure- ments of hydrogen ion concentration thus furnishes a check on other methods for guaging the fitness of water to sustain life. In nearly all of the localities examined, the water was found to be neutral or faintly alkaline. Some exceptions were noticed. At Scitico, the water of the Scantic River was distinctly acid (5x10-6 or p H=5.3) ; but this wa3 near

DISSOLVED OXYGEN AT A GIVEN POINT IN THE FARMING- TON RIVER, AS AFFECTED BY THE ACTION OF SUNLIGHT ON PLANTS.

DISSOLVED OXYGEN

Parts per Per Cent of Weather Hour Million Saturation

Sunny day ...... 8 A. M. 6.6 75 10 A. M. 7.0 79 12 M. 7.8 89 2 P. M. 8.4 97

Cloudy day ...... 8 A. M. 6.4 71 10 A. M. 6.4 71 12 M. 6.6 73 2 P. M. 7.2 81 the entrance of an effluent from a wool bleaching plant and not representative of the water of the river. A quarter of a mile below the mill the water was neutral, and at Hazards- ville, where a dam stops the further migration of shad, the water was faintly alkaline. At Rocky Hill and at Middletown, the water of the Con- necticut River showed a tendency to acidity. Every sample taken at these points either showed a neutral condition as contrasted with the faint alkalinity of the Connecticut River at other locations, or was faintly acid (p H, 6.8 or 6.9). Evi- dently, the volume of the flow of water in the Connecticut is large enough to prevent the development of any marked degree of acidity, even at places where organic fermentation is most pronounced. Weed beds in the river are, no doubt,

26 another factor in preventing acidity. They keep down the concentration of the carbon dioxide, which is one of the chief causes of acidity in polluted areas. The water of the Salmon River was found to be invariably acid on a falling tide (p H, 6.6 to 6.8). This is a slight degree of acidity, and is attributed to the tannic acid and other organic acids leached from woodland soil and from swampy areas bordering on this river. The yellowish color of the Salmon River water indicates this. The rising tide which sets up in the Salmon River as far as the Leesville dam is regularly accompanied by a faintly alkaline or practically neutral condition in the water. These fluctuations appear to have little effect on shad. The run of adult shad up to the Leesville dam, which prevents further ascent, is as good as might be expected, considering the numbers of shad in the general Connecticut River run. Shad eggs hatch in the Salmon River water. This was proved by practical propagation work. Artifically fertilized eggs hatched in floating boxes in the river at Leesville during 1923. Young shad were found in considerable numbers in 1923 and 1924 in this river, and their condition and rate of growth indicated thriving health. Possibly the hatching of shad eggs is not as successful in Salmon River water as it would be were the water not subject to an acid tendency. Leim, in his investigations on shad in Canadian waters, has found evidence that slight alkalinity favors the hatching of eggs, produc- ing a higher proportion of successful hatch and more vigorous embryos than can be obtained in neutral or faintly acid waters. But the applicability of these findings to conditions in the Salmon River is dubious, in that Leim's observations were made with infrequent changes of water which was not kept in motion during the egg development ; also, the water in the Salmon River is never markedly acid and is slightly alkaline part of the time. It is true that shad propagation at the Leesville hatchery was more successful in 1924, when alkaline brook water was used for hatching the eggs in jars, than it was in 1923 when river water was used. But the betterment of results was due in part, at least, to the cooler, and therefore more favorable temperature of brook water, as compared with river water ; and also, to the advantage of hatching jars over hatching boxes. Faint acidity was found in brook water entering the ponds used for retaining young shad at Joshuatown ; but the water of the ponds, which are rich in aquatic vegetation, was found always neutral or faintly alkaline. In general, then, measurement of hydrogen ion concentration revealed no conditions unfavorable to shad migration and propagation. 27 FOOD OF YOUNG SHAD. An important part of the shad investigation was a study of the food of young shad and its abundance in their haunts. Attempts were made to rear artificially hatched shad in live cars floating in the Farmington River. Some information was obtained in this way. The predominance of the embryos, glochidia, of river mussels in the food of the very young shad was demonstrated. In some cases the entire intestine of the shad embryo was found to be filled with a row of closely packed glochidia. The tendency of shad embryos to take actively motile small animals, insect larvae and small crustacea, as their food was also clearly shown by the examination of the alimentary canals of these confined embryos. It was also found that little or no vegetable matter was included in their diet. Such small amounts of plant structures as were occasionally found, probably represent material accidentally ingested along with animal foods, or present in the digestive systems of the animals consumed by the fish. Studies on confined embryos were not, however, very satisfactory, except for the earliest stages. After the shad had been in the floating live cars a few days, many were found to have little or no food in them. Their rate of growth was very slow and the mortality was very high. The largest specimens obtained in this way and the three best survivors of several hundred embryos placed in the ears were 26, 25 and 20.2 m m. in total length and about one month old. Several varieties of floating cars were tried and various modification of screening for the sides of the car in attempts to permit entrance of food to a maximum extent without allowing escape of the larval fish. A further at- tempt to increase their food supply was made by putting plankton towings into the live cars each day, but this ex- pedient also failed to cause satisfactory growth of the larvae. They appear to be voracious feeders and to range over the river bottoms in search of their food, so that con- finement can readily prevent them from obtaining sufficient nourishment. Better observations on the food of young shad were obtained by the use of retaining ponds for the larval and young fish. The ponds chiefly used were those constructed at Joshuatown for the specific purpose of retaining young shad. These ponds were constructed in 1895 and were stocked with shad embryos each season during the years 1896 to 1912, inclusive. After 1912 the ponds were not used for retaining shad until the beginning of this investigation in 1923. The embryos, then placed in the ponds, furnished much information as to their feeding habits. 28 But the observations that gave the most useful information about the food of young shad were studies of the gas- tric and intestinal contents of specimens taken in the rivers themselves. Catching of young shad appeared to be a difficult matter during the first part of these researches. The difficulty was due to the fact that young shad, even in the larval stage habitually remain in the deeper water of "holes" and are not to be found in the haunts of the young of most species of river fish. Three methods for catching the small larvae were used. One of them consisted in setting large funnel-shaped plankton nets of No. 1 silk bolting cloth in a submerged position in swift water, downstream from shad spawning areas. The nets were left in position from two to twelve hours and then carefully examined for shad eggs, shad larvae and coarser plankton. Another method employed a specially designed sliding dredge with net attachment. This was dragged along the bottom' from a row boat. This apparatus collected eggs but was not useful in obtaining the larvae. A third method was seining with a twelve foot minnow seine lined with one thickness of strong marquisette. This method, though use- less for obtaining eggs, was IV far the best means for catching the larvae. This seine, laid out just up-stream of a deep hole, was quickly drawn down through the hole to shore. It proved to be very efficient for catching larvae and could even be used to catch young shad up to 2 inches in length. But the best method for catching young shad after they are metamorphosed (about 25 mm. or 1 inch total length), proved to be seining with a 120 foot, fine-meshed bait seine. Several hundred seine hauls during the first half of the summer of 1923 fail to find any shad larvae. All of these hauls were made in comparatively shallow waters or near the river banks. They clearly indicate that young shad are not to be found in these localities. Numerous seine hauls, made later in the 1923 season and during the summer of 1924, scarcely ever failed to take young shad in the Farm- ington and Salmon Rivers. These hauls were made, however, in five selected deep holes in the Farmington and in four similar places in the Salmon River. Young shad were also found at Various times in the Connecticut, but here, also, they were taken only from deeper places. The evidence seems convincing that young shad even in the early larval stages, seek the bottoms of deep holes and habitually feed there, leaving them only for downstream migration. This migration was observed in the results of seining during the late summer and fall, and was actually watched where young shad could be seen in swift, clear water over light-colored pebbly bottoms. Like many species of fish, shad tend to 29 maintain a position headed upstream, but could be seen drifting down with the current. This occurred in the Farm- ington River in late August and September, but at other times no evidences of the presence of shad in shallower parts of rivers was obtained. The holes where they were found varied in depth from 9 to 20 feet. Clearly, then, food supplies in the deeper parts of the rivers, as well as sanitary conditions of the waters in these locations are of especial interest in connection with the shad problem. Data concerning the food eaten by shad in the rivers and retaining ponds were accumulated by microscopic examination of the contents of the digestive tracts of many specimens of larvae and young. Notes were taken on the food contents of 636 specimens, of which 150 were larvae held in floating live cars in the Farmington River. Of those taken in their natural habitats, 289 were from the Farmington, 60 were from the Salmon and 38 were from the Connecticut River. The others were from retaining ponds. The following table gives a summary of observations on the food of specimens from the last four sources. The actual proportion of shad consuming the organisms listed. is larger than is indicated by the tabulated values. This is the case because a considerable proportion of the fish are taken at a time when they happen to have little or nothing in the digestive system. This is especially true of the smaller larvae (less than 15 mm. in length) and was frequently the case among the small shad in retaining ponds where food supplies were inadequate. Also, many specimens were found with intestinal contents composed of one or only a few kinds of food, thus indicating that they had collected food over a limited area and therefore did not show a complete picture of their diet, or that a preference was indicated. The tabulated figures do show, however, some indication of the relative frequency of the consumption of the different food organisms in the several localities. For example, the importance of mussel glochidia in the Farmington River, of chronomid larvae in all places, of certain types of crustacea, such as Cypris in the Farmington and Bosmina in the other localities—is clearly indicated. The table also brings out the fact that various forms of insects and of crustacea are the mainstay of the young shad. Another fact of interest is that shad in the retaining ponds consumed more of the larger insect forms, damsel flies and dragon flies, and even non-aquatic insects which they must have taken from the surface, than did the shad in other places. This shows what happens when the normal food is insufficient. The meatier insect larvae and crustacea are the favorite food, as is indicated by observations on the Farmington River fish. 30 SUMMARY OF OBSERVATIONS ON FOOD OF LARVAL AND YOUNG SHAD. Figures show the number of specimens of fish which contained the organisms listed. Figures in parenthesis show the approximate percentage of occurrence of the organisms in the fish examined.

289 Fish From 60 Fish From 38 Fish From 99 Fish From Organisms Farm'ton River Salmon River Conn. River Retain's Pond

Mussel Glochidia 110 (38) 5 ( 8) Insect Larvae Chironomidae 190 (66) 26 (43) 27 (71) 42 (42) Culex 3 ( 1) 3 ( 5) Dragon fly 10 ( 3) 1 2 ( 5) 8 ( 8) Damsel fly 22 ( 8) 3 (55) 3 ( 8) 25 (25) Unidentified 34 (12) 9 (15) 3 ( 8) 9 ( 9) Insect pupae Caddis fly 9 (15) Midge 6 ( 2) Culex 2 ( 1) Perla 2 ( 1) Unidentified 4 ( 1) Insect nymphae Damsel fly 7 ( 2) 3 ( 3) Dragon fly 5 ( 1) 1 6 ( 6) May fly 4 ( 1) Libellula 2 ( 1) 5 (13) Insect eggs 40 (14) 5 ( 8) 2 ( 5) 3 ( 3) Non-aquatic insects 1 4 ( 4) Insect fragments Unidentified 40 (14) 10 (16) 12 (32) 15 (15) Crustacea Gammarus 1 4 (10) 6 ( 6) Alona 2 ( 1) Bosmina 17 ( 6) 43 (70) 15 (39) 33 (33) Cypris 80 (28) 4 ( 6) 6 (16) 12 (12) Ganthocamptus 7 ( 2) 6 (10) 3 ( 8) 2 ( 2) Chydorus 7 ( 2) 9 (15) 1 3 ( 3) Cyclops 25 ( 9) 4 ( 6) 18 (47) 9 ( 9) Sida 2 ( 5) 2 ( 2) Daphnids 21 ( 7) 5 ( 8) 5 (13) 2 ( 2) Diaptomus 6 (16) 1 Phyllopoda 1 7 (18) 3 ( 3) (fairy shrimps) Crustacean eggs 7 ( 2) 2 ( 5) 5 ( 5) Hydracarina 11 ( 4) 3 ( 5) (water mites) Plumatella Statoblasts ..... _. 10 ( 3) Round worms (nemas) 9 ( 3) 11 10 (10) probably parasitic.

31 In addition to the organisms listed in the table, small fish (various minnows and small sunfish) were found in the digestive systems of six of the shad from retaining ponds. Since no fish were found in any Farmington or Salmon River shad, and only one in Connecticut River shad, this probably is another illustration of the abnormality of the feeding of the young fish in the restricted area of a pond. Rotif era and Volvoxaceae, not often found in the river fish, were fairly common in the pond specimens. Quantitative aspects of the feeding of young shad are brought out in the following table which shows the numbers of the different food organisms found in each of 15 larval shad taken in a single collection from the Farmington River. The table shows what large numbers of organisms can be ingested by one small larva. They are obviously voracious feeders. Mussel glochidia, chironomid larvae, Cypris, Bosmina and Cyclops are, in the order named, the most abundant foods. The predominance of mussel glochidia is greater in this collection of fish than in many others. This is probably explained by the small size of these fish (12.5 to 21.5 mm. total length. After metamorphosis, which occurs at a length of about 25 to 27 mm., the young shad seem to prefer insect larvae and crustacea for their food. With this exception, the values in this table are representative of many results obtained with specimens collected in various places. FOOD OF THE LARVAL SHAD TAKEN FROM THE FARMINGTON RIVER NEAR LOOMIS INSTITUTE 1 7" -iv Total -a DI 4 A • I 1 V length _ -.Z. = e: 614 , mm. % I; .5. 1 g .. T; I I T ..>, Q. PI I': G P.., S •, E-, °' 5 12.5 3 3 1 1 8 13.5 1 8 1 1 11 14 1 1 1 1 4 15.5 14 4 1 1 3 23 Crustacean eggs, Nema 15.5 1 6 7 16 3 9 2 9 1 1 1 26 Nema 16.5 3 10 1 2 16 Crustacean eggs 17.5 17 4 1 2 24 17.5 14 4 1 1 3 3 26 18. 25 4 1 1 2 .33 18 5 12 1 9 1 2 1 2 2 35 18 15 16 1 2 14 1 49 Crustacean eggs 19.5 45 8 2 1 56 Crustacean eggs 20.5 10 9 1 1 4 1 26 21.5 38 11 3 2 3 1 58 Total 195 109 7 26 4 8 31 14 8 Aver. 13 7 2 2 1 32 From this table, one may see how rapidly the food consumption increases with growth of the fish. For example : Total number of organisms in 7 larvae (12.5-16.5 mm.) 95 Average number of organisms in 7 larvae (12.5-16.5mm.) 13 Total number of organisms in 8 larvae (17.5-21.5 mm.) 309 Average number of organisms in 8 larvae (17.5-21.5 mm.) 36 In short, a growth represented by a body length increase of about 35 per cent, a growth accomplished at this stage of development in about one week, is accompanied by a food- capacity increase of nearly 200 per cent. Such a relation- ship is not peculiar to these fish. It can be observed in various kinds of rapidly growing young animals. The abundance of the organisms eaten by the shad was studied in numerous localities. In the deep holes of the Farmington and Salmon Rivers, an abundance of insect larvae and small crustacea was found. It was not difficult to discover the correlation between the abundance of a certain species in a given locality and the frequency of the occurrence of the species in shad food. For example,— Cypris was obviously abundant compared to other crustacea in the Farmington, while Bosmina was found in greater numbers in the Salmon River. Correspondingly, Cypris is much more frequently found than are other crustacea in Farmington River shad, while Bosmina is the prominent article of food for Salmon River shad. Also, a scarcity of crustacea, other than Bosmina, was observed in one of the Joshuatown ponds in August, 1923. Correspondingly, the shad of the pond had few crustacea in them and were found to be feeding mostly on insects. In general, then, the examination of water and bottom samples can give a useful index of food available for the fish. This index can be made a quantitative one only with great difficulty in this case, because the organisms which would need to be counted are so motile and so unevenly distributed that an exact numerical index of their abundance would require extensive observations. There seems no question, however, but that food for young shad is fairly abundant in the Farmington and Sal- mon Rivers. The nutritive condition of specimens examined confirms this. Shad taken after they had passed the larval stage, were almost always filled with food. A study of the rood of the food of shad, that is,—observation of what is consumed by the animals which shad eat, helps to determine the fitness of the rivers for sustaining the fish. A study of the food contents of insect larvae and

33 3 small crustacea, shows that they consume the minute green plants. Typical observations are the following: Mougeotia Fragilaria found in chironomid larvae, found in shad. Melosira Mougeotia ( Bosmina 1 Other algal filaments Cypris found Diatoms of several kinds found Cydorus in Scenedesmus in .1 Cyclops shad Various Desmidaceae Daphnia Protococcaceae LOther Crustacea 1 Other more complex relationships are possible, though difficult to prove. For example,—minute plants, such as protococcaceae, Desmidaceae and Diatomaceae, may be eaten by rotifers, protozoa and other microscopic animals which are eaten by insect larvae and small crustacea which, in turn, are eaten by the young fish. But whatever the chain of food relations may be, the minute diatoms and green plants are the pasturage which directly or indirectly feeds the animal life of the water. In a sample of ooze dredged from the bottom of a shad populated hole of the Farmington River, the following forms were rccognized: Diatomaceae Navicula Fragilaria Nitschia Epithemia Asterionella Melosira Synedra Cocconeis Pleurosigma Surirella Tabellaria Chlorophyceae Closterium Mougeotia Stigeoclonium Pleurotenium Spyrogyra Ankistrodesmus Sphaerozosma Pedisatrum Scenedesmus Protococcaceae Cyanophyceae, very few Oscillatoria Protozoa Astasia Stentoi. Actinosphaerium Trachelomonas Actinophrys Arcella Euglena Amoeba Centropyxis Nuclearia Halteria Various ciliates Rotifera Diglena Monostyla Distyla Vermes Nematodes (few) Naids (few)

34 Gastrotricha Chaetonotus Crustacea Cypris Chydorus Daphnia Candona Alona Simocephalus Cyclops Oxyurella Bosmina Adult form and Acroperus Sida Nauplius Eurycercus Mollusca Glochidia of mussels and clams Insecta Larvae of chironomidae Maggots of flies Nymphae of mayfly, damselfly and dragonfly. This list is comparable, though of course not identical with many similar ones prepared from microscopic studies of bottom samples taken at "shad holes", and illustrates the feeding associations of the river flora and fauna. In general, the food found in young shad is made up of animal forms that can be found on the bottom of the deeper portions of the river, but it is possible that they do make brief excursions into shallower places in search of food. This possibility was suggested by the observation of Bosmina Longirostris in shad intestines. This species of Bosmina is commonly found in weedy places along the banks and is not apt to be near the bottom of deeper places. An- other exception to the general rule was suggested above in connection with the food of young shad in retaining ponds. Here the fish appear to eat organisms taken at the surface. But under perfectly natural conditions, bottom forms of insects, in larvel stages, and of small crustacea are the chief food of young shad. GROWTH OF YOUNG SHAD. The growth of young shad is fast. It may even attain a rate measured by an increase of one inch in length per month. The larvel shad as first hatched averages 10 mm. in length. The largest specimens of young shad taken during this work were 118 mm. (taken September 10), 98 mm. (taken August 28) and 98 mm. (taken September 15). As the earliest hatching probably does not occur before May 10, these specimens could not have been much, if any, more than 4 months old. Thus, a growth of 88 to 108 mm. was accomplished in about four months, or at an average rate of 24 mm. per month. But this is exceptional. The average length of 74 specimens of young shad taken from the rivers between August 23 and September 15, was 60 mm. The

35 spawning period covers no less than two months, and may even extend over a period of ten weeks from about April 27 to about July 5. The evidence, indeed, indicated that these were the limiting dates in 1924. Because of the length of the spawning period, young shad of any given catch may be of comparatively differing ages, so that no definite conclusions can be drawn as to their rate of growth (see Figures 10 and 11.) Some indication of the rate of growth during the early and middle portion of the season can be seen in the curve of Figure 12. The growth curve appears to be steeper during July than in August. Whether this is in- herent in the growth performance of the shad, or is due to the relative abundance of food, or to both these factors, is not apparent. All the fish, about 700 in number, of which measurements were included in the compilation of this curve, were taken from the Farmington River in 1924. They appeared, in general, to be well nourished. It is thus of interest .to compare growth, as registered in this curve, with that in retaining ponds and other localities. In the Salmon River, three catches of young shad had average lengths which fell on this curve for Farmington River shad. Other Salmon River catches, taken later in the season, were about the same in average size as those obtained on comparable dates from the Farmington. It seems probable that both of these rivers support good growth of young shad. In retaining - ponds, however, results were somewhat different. During July and early August, the average sizes of shad catches increased in the ponds, but during the latter part of the season the pond fish appeared to almost stop growing, in that the average size of samples scarcely increased as the weeks passed. The following tabulations show this point: MEASUREMENTS OF THE TOTAL LENGTHS OF YOUNG SHAD TAKEN FROM PONDS AT JOSHUATOWN.

Number Maximum Minimum Average Date of Fish Length Length Length Caught m m. m m m m. 1923 July 10 ...... 4 35 30 335 26 ------27 49 28 35.1 Aug.,, 16 ------7 35 29 32.2 28 ...... 59 65 27 37.6 Sept. 2 ------..... 16 38 33 35.0 1924 July 7 ...... 83 35 16 25.3 f 9 30 ...... 72 44 18.5 24.9 Aug. 9 ------43 68 28 40.0 ,, 16 ...... 121 80 29 34.8

36 Fig. 10.

Fig. 11.

Fig. 10. Shad fingerlings 31 mm. to 70 mm., seined in one haul from their natural habitat in the Farmington River in August, 1923. Fig. 11. Shad fingerling ready for migration to the sea. Length 97 mm. EVY6' 7W5 ca (5/162, C/7 re H //Y -A .41

Fig. 12. Graph showing rate of growth of young shad. At a time when little shad taken from the rivers were averaging 60 mm. in length, those from the ponds averaged 35 mm. This agrees with the observations on the stomach contents and general feeding conditions of the retained shad. ENEMIES AND PARASITES OF SHAD. The mortality of larval and young shad is probably high, even under favorable conditions. No satisfactory estimates of its extent were obtained. Experience showed, however, that at a given place, a single short haul of a small seine in June, might catch a hundred shad larvae, while a haul made as nearly as possible at the same place and in the same way a few weeks later, would take only about a score of young shad. This may be due in part to their better ability to escape the net as they become larger. It is not the effect of the seining itself. The proportion of any one "shad hole" covered by a seine haul was a very small one. The result appears to be an index of actual loss of the fry, because they do not show signs of migrating at this stage, and because a considerable proportion of them are found without food, thus indicating that they are weaker than the well-fed ones. Larval shad are very delicate organisms, soft and without external protection. Scales do not appear until some time after metamorphosis is complete. There may readily be some loss from mechanical injury, in addition to deaths from undernutrition. Death because of predatory animals is also a possibility. Against this, a shad's only protection is its remarkable swiftness of motion. Even the larvae can dart about with almost lightning-like speed. But the speed of pickerel is also very great, and pickerel are abundant in the Connecti- cut and its tributaries, and in the retaining ponds used for shad. It was supposed at the beginning of this investigation that pickerel were serious enemies of young shad. Observations, however, modified this supposition. Exam- ination of the stomachs of 37 pickerel caught at different times and localities along the rivers, did not disclose any shad in the pickerel. The fish found were mostly minnows ; suckers and a few others were also found. Yet pickerel can surely eat young shad under some circumstances. When the ponds at Joshuatown were drained to let out the shad, many fish lagged behind until the water had drained to a low level and fish were densely crowded in the small volume of water remaining in the pond. Pickerel taken at this time from among the crowd of little shad were found to have shad in their stomachs. In one lot of 12 pickerel, 4 shad were found. One pickerel only 175 mm. in total length had swallowed a shad of 65 mm. total length. Obviously,

37 the failure to find shad inside of pickerel taken from the rivers does not prove that shad are never eaten by pickerel in their natural habitat, but these observations strongly suggest that pickerel do not normally eat shad to any great extent except under confined conditions. Smaller larval shad, if eaten by pickerel, might be digested so rapidly as to escape detection, so that these observations do not bear upon the question of the menace of pickerel for shad in larval stages. Eels might be regarded as enemies of shad. Observations during this work gave little information on this question. Eels are supposed to eat shad eggs. Based on the bottom- feeding habits of eels, that supposition is justified. Exam- ination of 27 eels, taken at different localities and varying in size from 85 to 480 mm. length, failed to disclose any young shad, shad larvae or shad eggs in the contents of their digestive systems. The fish found in eels were mostly minnows. The chief food of these eels was made up of insect larvae and crustacea, so that eels are competitors, if not dangerous enemies of shad. Other potential enemies of shad are parasites. Practic- ally all adult shad are parasitized. Of 65, especially examined for parasitism, only 2 were found to be free from parasites. Identification of some of them is given in a paper by Linton (see p. 61). Parasitized shad appear to be healthy and well nourished, so that this species, like many other kinds of fish, endure parasitism with little ill effect. Another form of parasitism found in shad also appears to be harmless. The minute, free-swimming larvae (glochidia) of river mussels, attach themselves to the gills of shad. They are nourished and grow in this shelter until they drop off to begin their life on the river bottom. A photograph of shad gill tissue "infected" with glochidia, is shown in Figure 13). In thus carrying the young mussels, the shad appear to benefit their species indirectly, in that a plentiful population of river mussels insures abundance of glochidia in the water throughout the long spawning season of mussels. The glochidia, as shown above, are an important item in the diet of larval shad. Altogether, this investigation has not disclosed any serious menace to shad from natural enemies.

ARTIFICIAL PROPAGATION OF SHAD. As the results of these investigations show that, in the main, conditions in the Connecticut River and lower tributaries should permit shad migration and propagation, the

38 Fig. 13.

Fig. 13. Glochidia of river mussel shown attached to gill filaments of adult shad at spawning season. Glochidia when free swimming are important food elements in the diet of the shad larvae. decrease in the numbers annually caught seems to be due either to a failure of shad to get back from salt water into the Connecticut or to a discrepancy between the d2ath rate of shad and their propagation rate. The first of these causes is at present beyond the control of state agencies and is difficult to gauge because of lack of information. As to insufficient natural propagation, reasons for believing it is one factor in causing shad deficiency were given above and are discussed in the Biennial Report of the Connecticut State Board of Fisheries and Game for 1923-1924. This deficiency can be made up only by artificial propagation. Results from propagation work, that is, increases in the abundance of shad in the annual runs, cannot be expected to follow the work until some five or more years have elapsed. This appears from investigations of the ages of the shad entering the Connecticut River during the season of 1924. These investigations are reported in detail by Borodin (see p. 46) and Barney (see p. 52). About 250 shad were examined for age determination. The youngest were found to be four years old with the exception of one specimen, a small male, three years of age. But approximately 80% of the shad were five, six, seven or eight years old. A few (12 (;•:. ) were nine or ten and two specimens were eleven years old. The females, yielding roe of the more salable sizes, were at least seven years old. Eight year old ones were the most numerous among the roe shad. It seems likely then that shad do not commonly return to the river to spawn until they are five years old. That they may subsequently return annually for a number of years is indicated by microscopic examination of their scales and otoliths. (See p. 50). The number of times that an individual shad does actually come back to the river can be determined by any of a number of circumstances :—how long it escapes being caught, how suc- cessfully it escapes its enemies in salt water, or how long it remains in a part of the ocean from which it is able to migrate to its natal river. It would therefore be impossible to compute the number of adult shad which might be expected to enter the river during a given season even if the total number of fingerling young shad produced on each of the eleven succeeding years were known. As the success of natural propagation cannot be gauged and allowed for, and as the proportion of fingerlings actually produced from a given number of fry can only be conjectured, no satisfactory prognosis of the expected shad runs can be made on the basis of either natural or artificial propagation. Neverthe- less, there is a certain rough correspondence between the number of fry artificially hatched and the catches of shad during subsequent years. The curves shown in Figure 14 39 and the values given in the accompanying table indicate this correspondence. For example, the large number of fry (37,556,000) planted during the years 1896, 1897 and 1898, an average of over twelve millions per year, was followed by catches of shad which annually exceeded one hundred thousand during the period 1900 to 1905 inclusive. Other less pronounced correspondences are discernible from the curves. But, on the other hand, some marked discrepancies are fairly apparent. For example, fry planted during the period of eight years (1899 to 1906 inclusive) averaged 4,800,000 per year and yet the total catches decreased, with one slight exception, from 1904 to 1911. A possible explanation of this discrepancy has been revealed by the present investigation. Enormous losses of fry occur in the overcrowded retaining ponds in which nearly all of the larvae hatched during the period in question were placed. It may be, then, that the numbers of fry planted are not representative of the numbers of fingerlings liberated into the river. Another discrepancy can be seen in the increase of the total annual catches during the period 1915 to 1919 without a corresponding rise of the amount of preceding propagation work. This may be due to any one or more of several causes. For one thing, the number of nets used for shad fishing and the number of men employed increased during this period. In 1919, when a peak of the curve was reached, more hauling seines and more men were recorded as employed in shad fishing than during any other year since 1907. The price of shad rose sharply during these "war years" and thus gave added incentive to fishing. These increased catches, then, may indicate more intensive fishing rather than an increased abundance of fish. This seems all the more probable because of the shad scarcity during the following years (1921 to 1924) and the reported decrease in average size of shad taken. Other possible explanations are improved natural propagation or increased tendency of adult shad to find their way into the mouth of the Connecti- cut. It must be admitted that the data used for construction of the curves of Figure 14 are subject to criticism. The data for total annual catches are obtained from the written reports made by individual fishermen in accordance with the regulations of the State Board. To what extent some of these individual reports are mere estimates there is no evidence. The data for the numbers of shad fry planted are based on measurements of the volumes of the collections of shad eggs for hatching and the less accurate estimates of the proportion of the eggs which actually hatch.

40 I WILIPPIMMIUMEFrarnanariai MU=•MN•EMMIIMMEMME•MEMMEMMENOWIN MINMErnalMOMMERVATIEN•I rITIMEMPEEMBEIVL ••••••••• MEERMIM EMI • MIIIIIIIIIIIIIIIIIIIIIIIIIIIIIp 11III UNMPULIPI INNEMUIPMEM ME= OEM =UM =OM EMBEIMIligMAIII MOM MUM••••••••••••••••••••••••••••••=i0111ME IMMISOMMUMMEMENNIUMMEOMMEMEMMEMEMMEMONEWM IHNIIIIMMIIIIMI 1M IMMOINEEMEMMEMEMMEMEMEMERUSW, RIMINUMMEMEMEMENEMEMMIP MEW MU MI INTIMEEMEMEMMIMMOWN7 I EOM ME ERNE11 • MOM M WILIMMEMMEEMMEmei IlmmEMENMENOMEN MO mil • mmEmmEMEMEmEMIMIN IIIIMMEMMUMEMITI IIIIIIIWRIMMENNEM I IlmmiThEMOM M IIIIIIIIIII 11111111111111111111. 111111111■■■•••• • WM= EIMUMEM al Iq ruplauromintquess 1 MilimpLINELLAMILICEM ••• moms IMMEMEM =Ern OEMMEMEMEMINNUMWMOMM MINEMEMMEMMILMMOMMIMEMEMIMMEMOMMINEWIUMEM HIMMUMMUMEmmiMmEmmUMUMUMEMMEMEIMNIMEMEMEm IMMEMIMEMMOMMUMMIUMMUMMUMMOMESEEM IMEMmummEMEMEM======••=011=EN • mEEMMEMEMEMEMEMEMEMMEMINUMMOMEMOWIME • IMEMIMMIMUMMEMMEERMEMIEMEMEMMUMENNUMMOMEr ENIMME Mill§m§MMEMEMEMEMEMIERMAgENMEmmW" EIMMEmom MMENIMEENMEMEMMIMEMEEMEMEEMMEMESIVIWA IIIIIIIIIIIMIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIMEM MUMMEMIMMIROMMEMENIAMMEMMEEMMETWIMMOM MMErnimmEMEMMEMEMEMEMOMMUMMOMEM WrAMMEMESTM EWE= EljEllnffer======.11WWIENEMEMAI Illmmil= MmOntsw--MUSEMOMMEMMICOMPAMOMEEMPAI OMMEMMEMEMEEKLIMMUNIUMEMEMENUEMINWOMEMNIMPAI MIUMMEMEMMEMLEMMENIMIMMUMEMIONMOSTIMOMMIOTME IMMEMIMMENFAMMEMEmmEMEMEMEMEIMEgpOwComMERWILIArEM MEMOMMEMEMIRWEMEEMMEMEMEMMUMFMEamMEMEkl■arnill EMNIMINIEWASOMEMEMMEMITIMMOI-..WAREEMEMERaMmEm= InmEMONEMMEMEMMILMMIRM.a0MUOMMISOMIWWMOOMEM •••0111••■•••PERWIErpprnifilanSWEIR 1101. • RM ammlm mm m ,„m mmommommm ivs mommomm mm • ••mai.—11., 4.... m .11.. 1:11112111-1.1 IIIIIIIIIIE AIIIIIIIIIII 11llIdd IIIIII FIIIIIIIIIIiiiiiiiiiIIIIIIIIIIIIIMEIIIIIII Wm. - mum. 111111• mm41.411...... 4161 immo_mimems mmummommomm=1111p11111komm • 111111=mom%1IMMEIRMIPPPIIMMENINII NOMMIME MININUMmiligmmmemommm_Img ..olostI_momv MEMEMMINUrnialLMOmm. -maammomwm-ummum mmmmmmmmmmmmmmemMiimmm•csmgmmmmmmmmmmmimmmnm 111111.11111111110111111111/0411111111P11111 m m ilim IMINEMMOWEANRoo.,_MINE foRMAMENNew: m mil ...... w...mammem.....ME .....1...... m.n.....1..7.....m...... a.....mmamimm ...m...... m.....meremm..... Sti ...... MEMEIMMUSIRENESQR■SEMIEME IIIRESTRUILEMERMINIONFOLNEZEMmummmi m mm mmommum mommommmmimmillarr mom= mmEmEMMEMINIMMEll ol o MEW! § ffi in 11111411111111111116 .. .01.11 mal WA.= ME • • EmilIMME•• m ME 11:111111111.11112M1111_ . co gy

Fig. 14. Graph showing correlation between the annual plants of fry and the annual catches of shad as reported during the past 30 years. But when all allowances are made for these uncertainties, one still sees clearly that artificial propagation must be carried on at a much higher rate than was attained on the average in Connecticut during the past two decades, if it is to compensate for man's interference with natural reproduction. Obviously, artificial propagation is only one of many factors which have to do with the relative abundance of shad, although under the conditions, prevailing in Connecti- cut, it is an important and significant factor. During the shad season of 1924, intensive efforts to obtain spawn resulted in the hatching of a larger number of fry than had been produced during any of the past twenty years. Plans for further extension of spawn-taking and for increase of facilities for hatching in future years were presented in the Biennial Report of the Connecticut State Board of Fish- eries and Game for 1923-24. If these plans prove to be fruitful, the discrepancies which have existed between the amount of shad-fishing and the amount of artificial propagation may be overcome. Even if the propagation work can be maintained at a rate no higher than that of 1924, the abundance of shad in the Connecticut might be expected to increase in comparison with that found during the past few years.

41 SHAD CAUGHT AND FRY PLANTED IN THE CONNECTICUT RIVER AND TRIBUTARIES.

Numbers of Numbers of shad reported in Year shad fry planted total annual catch

1890 4,309,000 34,318 1891 1,906,000 22,462 1892 1,362,000 18,965 1893 1,251,000 41,253 1894 4,590.000 72,398 1895 2,611,-000 62,597 1896 11,456,000 57,318 1897 13,000,000 73,367 1898 13,100,000 93,450 1899 4,800,000 94,615 1900 6,000,000 114,182 1901 5,978,000 124,947 1902 3,000,000 107,208 1903 3,000,000 176,085 1904 7,135 000 172,436 1905 3,900,000 120,358 1906 3,000,000 72,394 1907 1,013,000 38,880 1908 435,000 49,031 1909 660,000 34,972 1910 938,000 28,042 1911 642,000 27,640 1912 1,000,000 60,064 1913 52,053 1914 58,057 1915 218,000 41.377 1916 106,000 52,696 1917 1,160,000 64,766 1918 1,160,000 68,918 1919 696,000 82,303 1920 540,000 50,312 1921 169,000 21,191 1922 13,821 1923 500,000 13,350 1924 3,751,000 25,316 In connection with propagation work a study has been made, during this investigation, of the usefulness of retaining ponds for the protection of shad in their larval and fingerling stages. This was done in former years by placing the fry in the retaining ponds constructed for the purpose in 1895 at Joshuatown, near the banks of the Connecticut River, in 1899 at Stratford, also near the Connecticut and in 1895 at Poquonock, on the Farmington River. In these ponds, chiefly the ones atJoshuatown, shad fry were retained each summer from 1895 to 1912. Results, in the form of well-grown fingerlings liberated into the rivers each fall, were regarded as excellent according to the reports of the Connecticut State Board of Fisheries and Game. But no

42 accurate observations were made to determine the actual success in terms of the numbers of shad fingerlings liberated. After 1912 the practice of using retention ponds was discontinued. It has been tried again during the past two years at Joshuatown and on a small scale at the hatchery pond on the Hammonasset River. The fish have been examined at suitable intervals to watch their growth performance. As explained in connection with the discussion of the food of young shad, they soon showed signs of food scarcity. Not only their poor rate of growth and their empty or half empty stomachs containing abnormal foods were noted, but their obviously stunted condition was clearly seen toward the end of the summer of 1923. Their heads were dispro- portionately large for the size of their bodies, the eyes were prominent and obviously big in comparison with shad of the same length taken from a natural habitat. The bodies were slender and starved looking. The following measurements of two shad of the same total length, one of them from the Farmington River and one from a retaining pond, are typical, and illustrate the ema- ciation of the "retained" specimen.

Specimen Specimen from river from pond

Total length 30 m m. 30 m m. Weight 9.8 g. 8.6 g. Head length 7.0 m m. 8.0 m m. Head height 5.0 m m. 5.5 m m. Diameter of eye 2.5 m m. 3.0 m m. Appearance of eye not projecting projecting The young shad in the ponds were obviously undernourished. Observations on the microscopic and small fauna of the ponds showed that the supply of the favorite foods of young shad, crustacea and larvae of aquatic insects, was deficient in comparison with the rivers. This was true of the latter part of August and September, although the ponds were abundantly supplied with these food organisms earlier in the season. It thus appears that the rapidly growing and voracious shad had largely depleted the food supply in the ponds in about six weeks. The depletion was due, in part, to the presence of other small fish, for although the ponds were drained each year before the shad season, they were not freed from pickerel, sunfish, perch and bull- heads. The young of these species, especially of sunfish, together with many minnows of several species, were numerous in the ponds, though not nearly as abundant as young shad. To some extent these species were food competitors of the shad.

43 In such an undernourished condition, the mortality of young shad was probably high. No satisfactory method for estimating it was found. Only a few dead ones were seen in the ponds, but this is not significant, because the ponds were June. 1924, not more than 30,000, or five per cent of them appeared to survive. This estimate is based on trial net- tings made in the outlet of the pond on August 21, while the well populated with crayfish. These efficient scavengers would eat dead fish before they floated to the surface. Of 630,000 fry placed in one of the ponds at Joshuatown in fish were being liberated into the Connecticut River. It is a rough estimate, however, and merely indicates very considerable losses of shad in the pond. This raises the question of advisability of the use of retaining ponds. But it should be remembered that a very heavy mortality occurs (see p. 37) during the early larval stages, and at this period, waters that are free or nearly free from enemies, should afford a real advantage to the fry. On this account, the use of retaining ponds seems justified, but certain precautions in their use are important. Either the fish should be liberated shortly after they are metamorphosed, at an age of about six or seven weeks, or else, the retaining ponds should be planted with fewer fry than were introduced into the ponds during this investigation. The limits between a safe number and overstocking would need to be determined by further observation, but would undoubtedly be much lower than the numbers planted at any time in the past.

Summary This investigation has included some extensions of previous studies on shad development. Biological and chemical examination of the waters of the Connecticut and its lower tributaries has shown that, in general, conditions are favorable for shad migration and propagation. But parts of the Connecticut River itself show the bad effects of pollution chiefly due to the sewage of Hartford and Middletown. The food of young shad, their habitat in the rivers, their rates of growth and their migration have been studied. The ages of adult shad entering the Connecticut have been determined by studies of the scales and of the otoliths. Parasites and other enemies of shad in the rivers have been investigated. The result indicated no serious danger to shad.

44 Data are presented to show that artificial propagation, aided by a judicious use of retaining ponds, promises an increase of shad abundance providing overfishing of shad is prevented by suitable restrictions and provided pollution is not allowed to produce effects worse than the present ones which have made certain areas of the Connecticut River un- suitable for shad spawning. Regarding restrictions, specific recommendations were made in the biennial report of the State Board of Fisheries and Game for 1923-1924. The recommendations aim: (1) to increase the chances for adult shad to reach the best spawning places, (2) to favor the chances for natural spawning, (3) to avoid methods of fishing (use of set nets) which do not permit conservation of ripe spawn, (4) to secure the co-operation of fishermen in spawn-taking and (5) to increase the amount of artificial propagation.

IT) PART II.

AGE OF SHAD (zILOSil S'APIDISSI111..1 WILSON) AS DETERMINED BY THE SCALES.

By PROF. N. BORODIN. The study of shad scales was made during the Winter of 1923-1924 and the Spring of 1924 as a portion of the work of shad investigation, undertaken by the Connecticut State Board of Fisheries. Previous Work. I could not find in the literature any record of the study of shad scales from the point of view of age determination. Dr. T. D. A. Cockerell, when examining scales of different fishes from the taxonomic point of view, gives a short description of the scale of the shad (Proceed- ings of the Biological Society of Washington, Vol. XXIII, pp. 61-64, 1910). In his other paper (Smithsonian Misc. Coll. Vol. XVI, P. 2, 1912) there is a drawing of a shad scale, but it was taken, probably, from the caudal peduncle and is not typical of shad scales. There are several works on scales of herring, which be- longs to the same family, Clupeidae. Knut Dahl' and Einar Lea" have reported detailed work on the herring scale as a means of determining age, growth and migration of this fish. They have also published a description of methods used by them. A. Nedoshivin and M. Tihy used scales for the determination of age of the Caspian herrings (Caspialosa Berg'). When dealing with herring scales, these authors evidently did not find any difficulties in reading the number of annuli for determination of age. Many thousands of specimens were examined by them and the results are presented in many tables, which accompany the papers. There are also many drawings of scales, but only three photographs. (1) Knut Dahl. The scale of the herring as means of determining age, growth and migration. Rep. on Norwegian Fisheries and Marine Investigation, Vol. II, 1907, p. 6. (2) Einar Lea. On the method used in the herring investigations. Conseil permanent internation pour l'exploration de la mer. Publications de Circomstance, 53 (1910). (3) Einar Lea. A study of the growth of herring Ibid. 61 (1911) and 66 (1913). (4) A. Nedoshivin and M. Tihy. The determination of the age of Clupionella caspia. Contributions to the knowledge of Russian Fisheries—Vol. XX, Part 6, 1923. St. Petersburg, (Russian).

46 Fig. 1.

Typical shad scale removed from male 5 years old, length 36 cm. B-C, length of scale. Fig. 2. Segment of shad scale showing markings used in determining age. A, anterior striated portion; P, posterior part of scale; B, boundary between the anterior and posterior parts; C, circuli; F, focus; a, annuli; R, radius; S, striae; (Striae cover entire anterior portion) Tr. Gr., transverse groove.

Fig. 3. Scale of shad fingerling 4 months old showing two incomplete transverse grooves. Method applied for determining age of shad. In the case of shad scales difficulties in counting annuli (Figure 1) arise at once. Some circuli may be confused with the annuli and only a few shad scales show annuli clearly. No treatment used in examining scales of other fishes is effective with shad scales : macerating, staining by picrocarmin, decalcifica- tion—all were tried, but without the desired success. I could not use polarized light because of the lack of equip- ment. I found after trying various methods that the best one to be applied to the shad scale is the simplest, namely : after soaking the scale in water and cleaning it of glutinous stuff by means of a brush, examine it for reading transverse grooves in water ; for reading annuli,—dry it flat on the object slide and examine it dry. Fresh scales are much easier to clean right away, by merely rubbing them between the fingers with cheese cloth. Being convinced by experience that counting only annuli is not always certain with shad scales, I tried to find some additional marks in order to have a possibility of checking the results and to make corrections. Besides circuli and annuli which are found on all other fish scales, previously examined, there are, on the shad scale, two kinds of other very distinct lines, namely : numerous parallel striae, running transversely and crossing annuli in the central part of the scale at about a right angle, and less numerous and more distinct transverse grooves running in the same way as striae, but not always parallel to them and having a different structure. Striae and transverse grooves are found on the scale of even young shad of a known age of 4 to 5 months. They have at least two grooves on each scale (2 mm. long) of young shad, (Figure 3). The grooves of larger scales are more numerous and in general, their number is bigger. The larger scales, generally speaking, belong to the shad of larger size. Comparing the number of circuli on the scales on which observations are clear enough, I found that the number of transverse grooves is always even and, noting that during the first year the shad scale has at least two complete grooves and its annulus is represented by the very edge of the scale—I thought that there is some reason to deduce that each following year there must be one annulus and at least two more grooves ; and so it is in reality. The number of complete transverse grooves, divided by two, gives the number of years corresponding to the number of annuli. I emphasize the word, complete, because if one counts all grooves the number will not correspond to the number of

47 years. They may show in some cases additional months of the next year, but to avoid miscounting and for simplicity's sake I neglect them in reading. To illustrate the method used, I refer to the drawing (Figure 2.) on which all lines and grooves are shown. To avoid misunderstanding I must say, that when examining shad scales I always count annuli as well as transverse grooves, so that one reading supplements the other. But in cases when annuli are not readable at all, I limit my- self by using only transverse grooves.

SOURCES OF SHAD SCALES USED FOR STUDY, ACKNOWLEDGEMENTS. My study of shad scales was begun at Hartford when the season of shad fishing was over (November of 1923). I have had plenty of young shad (fingerlings) and their scales, but not more than a dozen preserved scales taken in the Spring of 1923. I take this opportunity to express my thanks to Prof. A. Petrunkevitch of Yale University for his valuable advice and assistance in preparing microphotographs and to Prof. H. A. Swan and R. W. Storrs of Trinity College for loaning me a microtome, etc. I also wish to express my thanks to Mr. A. H. Leim, who shared with me his collection, to Dr. S. Hen- shaw and Dr. S. Garman of the Cambridge Museum of Com- parative Zoology, who permitted me to examine shad at the Museum, to Dr. H. W. Fowler of Philadelphia Academy of Natural Sciences and to the U. S. National Museum of Wash- ington in the person of Mr. W. C. Ravenel and Mr. B. J. Bean, who had delivered to me scales of very rare specimens of shad from salt water. Later on I got scales from shad pur- chased at New York fish markets including shad from the Pacific Coast, frozen ; from Florida and from North Car- olina. I examined 100 samples of scales, collected by the U. S. Bureau of Fisheries in 1916 taken from different places along the Atlantic coast, and finally 114 samples of shad taken in 1924 from the Connecticut River and Long Island Sound. Exterior view of shad's scale: diversity of forms; scales used for determining age. The accompanying pictures (Figures 1 and 4), give the best idea of the regular form of the shad scale, but in general the form is very diversified even on one and the same specimen on different portions of the body. Thus, it is very important for age determination to choose scales correctly and from about the same place for every separate fish examined. I have picked scales from the an-

48 Fig. 4 Typical shad scale of male 50 cm. long; 9 years old.

Fig. 5 Regenerated scale of shad, female, 54 cm. long. Fig. 6. Portion of shad scale showing annuli (a) and transverse grooves (tg) crossing them, x62. tenor part of the body at a point about half way between lateral line and pectoral fin. In fact, most of the scales on the body of the shad besides those on the belly, fins or caudal peduncle, are very similar and are what I call regular or typical in shape, though they are slightly different in size. No irregular scales were used for reading annuli and grooves. Besides scales of irregular exterior form, i.e. with irregu- larly shaped edge, scales very often occur with' irregular interior structure, as can be seen in Figure 5. These are regenerated scales, scales which replace the lost ones as the result of some bodily injury. These can not be used for reading annuli or grooves which all mixed up in a peculiar and complicated net of lines. Interior structure of shad scales. Though I have some cross sections and other preparations made from shad scales and several drawings and microphotographs, I refrain, for the present, from publishing this part of my study which I - hope to complete later. However, I wish to state here that transverse grooves running across the scale are really not accumulated striae, as it might be supposed by the analogy with circuli and annuli of salmon scales, but are really grooves on the surface of the scale, and when stained, they fill with stain and are more visible than any other lines. They are not always parallel to the striae and sometimes cross them at acute angles as may be seen in the microphotographs (Figure 6). On the other hand annuli are not on the surface of the scale, but are internal structures, that is why they are not as clearly visible as grooves. The annuli are always parallel to the side edges of the scale and in the middle portion of the scale they cross transverse grooves at right or nearly at right angles. (Figure 6). All that is said above relates to the anterior striated portion of the scale which is placed in a fish-skin pocket. The smaller sized posterior portion of the scale has no striae. It is transparent and has a frayed margin. There are radii running from the focus. All structures of this portion of the shad scale resemble very much the shell of a scallop. Posterior parts of circuli and annuli can also be seen very often on this portion of the scale (Figures 1 and 4). One important point about annuli must be mentioned; annuli of the first and the fourth year are always more distinct and have a different appearance from the others. They resemble "spawn marks" of salmon and the fourth annulus, probably, corresponds to the spawn mark, because male shad are mature when 4 years old.

49 4 Changes of form and size of scale with the growth of fish. The form of the shad scale undergoes important changes even during the first year. Later on, the form of regular shad scales remains constant, though there are variations in the proportion of the length to the width. By length of the scale is meant the measurement from the front tin of the scale to the apical or posterior edge (line B—C in Figure 1). Groups of shad arranged by size and age. Applying the above described method of determining age of shad by reading annuli and transverse grooves, we can state that the growth of shad, speaking generally, runs as follows:

Groups Number of specimens examined

I 26 Shad of size 5.8-11.3 cm. are in their first year II 4 Those of size 14.5-18 cm. are in their second year III 7 Those of size 21-29 cm. are in their third year IV 10 Those of size 30-35 cm. are in their fourth year V 22 Those of size 36-39 cm. are in their fifth year VI 22 Those of size 40-43 cm. are in their fifth, sixth and seventh years VII 43 Those of size 44-48 cm. are in their sixth, seventh and eighth years VIII 41 Those of size 49-52 cm. are in their seventh, eighth and ninth years IX 49 Those of size 53-57 cm. are in their seventh, eighth, ninth and tenth years X 24 Those of size 58-66 cm. are in their eighth, ninth, tenth and eleventh years Total, 250 (26 young, 92 females, 128 males and 4 unclassified). Specimens of sizes 5.8-11.3 cm. (group I) are summerlings, caught in the river, or taken from the retaining pond artifically hatched and reared. Specimens of sizes 11-29 cm. (groups II and III, age 1-3 years) are very rare and were all caught in salt water. In fact, only two specimens of 14.5 cm. were delivered to me from Long Island Sound; from all other specimens of these groups I had only scales and sizes. Specimens of groups IV and V are young bucks (males) entering the river. Group VI (size 40-43 cm., age 5, 6 and 7 years) consists also mostly of males (9 females out of 22 specimens). Group VII (size 44-48, ages 6, 7 and 8 consists also mostly of males (9 females out of 43 specimens).

50 In group VIII (size 49-52 cm., ages mostly 7 and 8 years) females are more numerous (13 out of 41). In group IX (size 53-57 cm., ages mostly 8 and 9 years) females are predominant (43 out of 49). In group X (sizes 58-66 cm., ages 9, 10 and 11 years) there is only one male (58 cm.) out of 24 specimens. All specimens of the groups IX-X were caught mostly in the rivers, few of them in brackish waters of bays and sounds, near the mouths of rivers. According to the figures of the foregoing table, supple- mented with the data on the time of catch, a few male shad (bucks) are coming to the rivers after attaining an age of 4 years (size 30-35cm., weight 200-300 grams) ; most of the males in the Connecticut River during the season of 1924 were 5-7 years old (size 36-49 cm., weight about 450, 670, 1000 grams, 11/2-21/4 pounds). Males are in general of smaller size than females (roes) and specimens of males over 53 cm. (weight 1750 grams) are very rare. Shad females (roes) entering rivers are 7 and more years old (size 43-66 cm., weight about 1300, 2000, 3000 grams). The largest specimen of roe shad obtained from the Con- necticut River region was 61 cm. long, 63/4 pounds or 3060 grams in weight. The smallest was 43 cm. long and weighed 821 grams. Most of the roe shad, caught in the Connecticut River during the season of 1924, were about 2000 grams or 41/2 pounds in weight. There is no difference in the age of the shad males and females of the same sizes. This statement relates to specimens of groups VII and VIII. There are still several missing links in the chain of records of growth of the shad females of ages 3-7 years. They are probably living in the ocean, are caught by the fishermen only occasionally and have not yet been examined for age determination. Scales of the shad, taken from the same part of the body of fish of the same size, are, generally speaking, of the same size. The larger the specimen, the larger are the scales, and vice-versa. The following table shows this very clearly, but the age cannot be determined by the size of scale only.

Lawthofscale Laigflioffish Laigthofsalle Lamthoffish man. am nun. cm. 1.5-3 5.8-10.3 11 35-36 4-5 14-17 12-13 39-46 7-8 18-26 • 14-14.5 49,-50 8-9 29-31 15 52-54 10 33 16-17 54-61 18-19 59-63

51 PART III A CONFIRMATION OF BORODIN'S SCALE METHOD OF AGE DETERMINATION OF CONNECTICUT RIVER SHAD. By R. L. BARNEY. Recent investigation has indicated that suitably chosen scales of the shad Alosa sapidissima may be used in age determination for this species. According to Borodin, the age of shad in years as determined by its scale is one-half the number of so-called transverse grooves on the scales. As this is a new method of age determination, confirmatory evidence appeared to be desirable. This led to a study of the otoliths of shad to determine, if possible, the accuracy of the method. The otolith has been of unques- tioned usefulness in age determination of a number of species of fish and it seemed that it might, therefore, serve equally well for the shad. Accordingly a large number of shad of various sizes and of both sexes were collected during the spawning migration of 1924 at several points on the Connecticut, the Salmon and the Farmington Rivers. The last two are tributaries of the Connecticut. These collections have been supple- mented by a few fish taken in Long Island Sound at other seasons. Records of length, weight, sex and sexual condition were made for each fish. The age of each fish was also estimated by examination of the scales according to Boro- din's method. The otoliths were then dissected from each fish. The otoliths of the shad may be easily dissected out by cutting off the upper part of the skull so that the cerebellum is laid bare. This cut is made from a point just above the eyes parallel to the long axis of the fish. The entire brain may be removed through this dorsal opening. Removal of the brain uncovers the inner ear. Careful lifting of the tissues on each side of the brain cavity causes the semi- circular canals to break and allows the sacculi containing the otoliths to be dislodged from their boney recesses in the floor of the brain case. The otoliths are very delicate and are broken if not handled with extreme care. Because of

52 Fig. 1. Otolith of Shad No. 112 taken at Orient, Long Island, N. Y., June 18, 1924. Length of fish, 14.3 cm. Note annulus (a), nucleus (b), and basal margin (c). their small size and because they are enclosed in the trans- lucent pink tissue of the sacculus they may be easily over- looked. The otolith of the shad is a minute bone of roughly sculp- tured surface and of unusual shape. In a shad 14 in. long the bone is of irregular, oval shape with two short, sharp points on the anterior end (Figure 1). In the larger fish these points become unequal extensions or processes of the bone. In shad of four or more years the otolith is divided into two unequal parts by a deep groove,running lengthwise of the bone. The relation of the parts gives the bone a notched appearance. One of the divisions becomes much longer than the other. An otolith, if allowed to dry, becomes very brittle and usually cracks along the groove. The "ear stone" of the shad has a shelving appearance due to successive boney accretions. It is slightly concave. The concave surface is comparatively smooth. The convex one varies. In an otolith whose length is 1.4 mm. the convex surface is a single rough ridge. Otoliths of fish of four or more years have a rough ridge extending the length of each of the two parts of the bone. The lateral margins of the older otoliths are rather deeply but smoothly scalloped. The basal or posterior end is smoothly rounded and somewhat heavier than the rest of the bone. The otoliths of adult shad rarely reach a length of five millimeters. Taken fresh from the head of a fish they are opalescent. They are also somewhat whiter than the other skull bones. The deposition of new bone occurs for the most part on the concave surface, each new layer extending slightly beyond the edge of the previous one. This manner of growth of the otolith tends toward making it essentially pyramidal in plan. Near the notch between the processes of the otolith is the center of growth around which are numerous fine concentric lines. Around this point the earliest deposits of bone are laid. The center of growth is termed the nucleus in the paper. It persists throughout the growth of the otolith and is useful in measurements. The shad otolith is not amenable to common histological treatment. If placed in nitric acid as weak as 0.25 per cent, it dissolves with effervescence rather than decalcifies. Evi- dently the bone is almost entirely made up of calcium car- bonate with but a minimum of organic material inter- spersed. This is the more evident when the bone is stained and examined in ground sections or in toto. Sections of otoliths prepared by grinding are unsatisfactory and stains are of no benefit except as they improve lighting effects. The mineral nature of the otolith and its lack of organic matter capable of differential staining make impossible the 53 use of otolith sections for age determination. Preparations mounted in toto in balsam without staining have been the most satisfactory. Examination of the bone in water or dry is of little value unless the bone has just been taken from the fish, for it becomes white and opaque very soon after removal from the sacculus. Microscopic examination of sections or of entire otoliths under low power shows numerous rings of growth due to the successive accretions of mineral matter. At first glance the "rings" or bands appear indefinite. The accretions seem to be laid on without apparent regularity. This impression is lost, however, when it becomes evident that otoliths vary considerably and uniformly with the size of the fish. Comparison of otoliths of shad of various sizes and of various ages, as estimated by scale characters indicates that there is regularity and uniformity in the process of deposition upon the otolith. The otoliths, even of adult shad, are so small that differences of size are not readily noticed by the unaided eye. Microscopic measurements, however, show the differences plainly. Table I indicates that the mean lengths of the otolith in shad of both sexes are in reasonable agreement with the ages as indicated by scale observations. In addition to this agreement between the length of the otolith and age of the fish, there is further evidence in the otoliths that the age estimate based on scale characters as reported by Borodin is correct. There are at hand specimens of Connecticut River shad varying in age, as estimated by scale study and by actual knowledge of the life of the fish from less than one month to ten years. This collection of fish contains an uncommon specimen of intermediate size between that of large fingerlings about to enter salt water for the first time and of small adults re- turning to fresh water to spawn presumably for the first time. The size and characteristics of the otoliths of this fish substantiate the scale method of estimating age. It is known that first year shad taken from fresh water in October and November are usually from 7 to 9 cm. long. The next larger shad available is the one mentioned above. It was taken on June 18th from Long Island Sound not far from the mouth of the Connecticut River. This fish is 14 cm. long. It must be, therefore, if hatched in early May, one year and nearly two months old. It assuredly cannot be younger. It cannot reasonably be supposed to be two years and two months old. The scales of this fish possess

54 a single annulus and two complete transverse grooves. This is as Borodin claims for a one year old shad. The facts concerning this fish furnish a basis for age determination by use of the otolith, for there is now available an "ear stone" of certain length, 1.4 mm. (.85 mm. from nucleus to basal edge), from a fish whose age is reasonably established at one year and nearly two months. This otolith is characterized, moreover, by a single well defined "ring" which appears very close to the margin of the bone. This "ring" is .8 mm. from the nucleus if measured on the basal end of the otolith. This is the first annulus. It should be noted that this otolith is of light color. The next older fish available is one which was taken from the Salmon River on June 17, 1924. This was a ripe male with standard length of 25.0 cm. Its scales indicate that it is three years old. Its otolith measures 3.4 mm. in length and substantiates this age diagnosis for it is characterized by a central definitely limited light-colored area which measures from its nucleus to basal margin .83 mm. It has been pointed out above that the fish of age one year and two months possessed an otolith of light color which measured .8 from nucleus to the first annulus. The definite line, therefore, in the otolith of this 25 cm. shad, limiting this central area and appearing at .83 millimeters distance from the nucleus, must be the first annulus. It is significant that in older otoliths the first annulus is always readily distinguish- able. Beyond it there are deposited two bands of bone. The first band exterior to the first annulus is a heavier and much darker band whose width on the basel edge measures .29 mm. The edge of this band is definitely lined and represents the second annulus. From the second annulus to the edge of the otolith there is a third band which indicates the growth of the otolith from the end of the second year to the time of catch, June 17, about the date of third anniversary ' of its birth. The third year's accretion is also darker in color than the first year's and measures .21 mm. in width. It is of significance that in all older otoliths examined the first annulus is surrounded by three similar bands of dark greyish brown bone, quite different in appearance from the light central region. The collections made during this investigation contain two male shad whose scales suggest that they are four years old. These were caught in April and May. As these months are included in the shad spawning season these fish must have been taken at about the date of the anniversaries of their birth. Their otoliths, as intimated above, are characterized by the typical first year light-colored central

55 area measuring approximately .8 mm. from the nucleus to the basal edge or first annulus. This central region is surrounded by three concentric dark bands. Of an otolith of one of these specimens taken April 21, 1924 the measurements of the widths of the concentric bands are as follows :- From nucleus to first annulus ------.91 mm. From first to second annulus ------.21 mm. From second to third annulus ------.18 mm. From third to margin of otolith ------.19 mm. These measurements are in satisfactory agreement with measurements made on younger otoliths. Here again it is evident that the annulus is laid down around the anniversary of the birth date of the fish. It is clear from this discussion that the age of shad up to and including four years as estimated by Borodin's method of halving the number of scale grooves is substantiated by the presence of annual rings in proportional number in the otolith. For older shad the otolith is no less confirmatory of the scale method of estimating age, although the increasing thickness of the otolith as age advances tends to cloud, to some degree, the earlier annuli. However, the first annulus serves as a useful landmark as does also the fourth. Con- tinued observation and measurements of a large number of otoliths have placed the first and fourth annuli at definite distances from the nucleus. If the measurements are made in the basal direction, these annuli occur at the following distances from the nucleus ; first annulus, about 0.8 to 0.9 mm., fourth annulus, about 1.5 to 1.7 mm. The fourth annulus like the first is very plainly indicated in older otoliths. Thus, in an otolith of a shad purporting by a scale observation to be five years old (fish taken on July 11, 1924) the fourth annulus is very definitely established at the edge of the three dark bands (second, third and fourth year's accretions). This broad, dark band containing three years' deposits stops abruptly near the end of the fourth year. The marginal band is of different character. Figure 2 illustrates the point. The fifth year band appears as a narrow lighter stripe on the exterior of the broad, dark band. The accretion occurring since the fifth birth anniversary date (May 30 to July 11) appears as a fine edge outside the fifth annulus. An otolith from a shad estimated to be six years old by its scale characteristics shows the one-and four-year landmarks well. The fifth and sixth years' accretions are plainly evident (Figure 3). An otolith of a shad estimated to be seven years old by its scale characteristics, shows the first and fourth annuli

56 Fig. 2. Part of otolith of a five year old male shad, No. 352, taken from the Salmon River July 11, 1924. Length of fish 39 cm.

Fig. 3. Part of otolith of six year old male shad, No. 349, taken from the Salmon River, June 24, 1924. Length of fish, 37.5 cm. Fig. 4. Entire otolith of nine year old male shad, No. 343, taken from Salmon River, June 24, 1924. Length of fish, 45 cm. First and fourth landmark annuli plainly evident. and three well defined stripes exterior to the fourth. In the microscopic examination of this otolith, the separation of the fifth, sixth and seventh years' deposits stood out more plainly when the microscope was manipulated so that the otolith image was alternately in and partly out of focus. A dark field with direct light sometimes assists in the study of the otolith. If this method is rapidly alternated with examination by transmitted light, the various bands on the edge of the otolith are seen more plainly. Usually the annual accretions are best seen in the regions marked X in the following plate. (Figure 4). In shad estimated to be nine and ten years old respectively by scale examination, the otoliths give a similar characteristic picture. The first and fourth annuli are easily dis- tinguished at a glance. From the fourth annulus to the margin of the otolith there are interspaced the remaining annuli. It will be noted that after the fourth annulus the additions to the otolith are not similar to the earlier deposited layers. Nor do the successive layers of the otolith after the fourth extend equally on all sides beyond the previous years' deposit. It is probable that the characteristics of growth and the color and density of various layers of the otolith are, in a sense, reflections of the conditions of life of the shad. At or near the end of the first year it appears from the otolith that some important change in food or habitat or in both occurs. The second, third, and fourth annual deposits are uniform in color and appearance and are respectively about the same width at the basal part of the otolith. These layers, however, are much darker than that included by the first annulus. It seems probable that the central light- colored area ending with the first annulus represents, therefore, the life of the young shad in fresh water. Juvenile shad have been taken from fresh water as late as November. The three dark bands encircling the light-colored area may represent, accordingly, the early life in the sea where growth is fairly regular and where the temperature of the water, and the kind and amount of food do not vary greatly. There is evidently a change in habitat or food abundance, or in the nature of assimilation or utilization of nutritive materials after the fourth year, for there is a marked change in the appearance of the otolith beyond the fourth annulus. This change may be due to attainment of sexual maturity. It is known that the buck shad* is ripe

*A single ripe three-years old buck shad has been taken from the Salmon River but this appears to be unusual,

57 at the end of the fourth year. On the other hand, however, the youngest ripe roe shad that has been taken in this investigation appears to be seven years old. Younger females probably do not migrate into tresh water to spawn. It is possible that they may spawn closer to the sea than do the older females and because of this they may be missing from our collections. In any case the otoliths of the shad do not give any indication that the habits of the buck and roe in this respect are different. In both males and females the first and fourth annuli are very prominent landmarks. It is worthy of note that Borodin has found similar characteristic landmark annuli in the scales of shad. Consider- ing this point he has written "annuli of scales of the first and fourth years are always more distinct and have different appearance from the others." Beginning with the fifth year's accretion the otolith of male or female shows a steady increase in size with quite uniform early additions and an appreciable change in color and appearance of the successive layers. This is due, it would seem, to a regular succession of events including life in the sea, the annual ripening of the fish and the spawning migration. Evidently the adult shad migrates to fresh water annually to spawn and then re- turns to an area in the sea where conditions year after year vary but little. Summary. The data here presented and the accompanying discussion stand as a reasonable confirmation of Borodin's method of estimating the age of Connecticut River shad. The confirmation is based:- 1. On the size and appearance of an otolith of an immature shad whose age has been reasonably established as one year and about two months and whose scales possess a single annulus and two transverse grooves. 2. On the presence in the otolith of this shad of a single definite annulus near the edge of the bone. 3. On the presence of annuli in the otoliths of shad representing the annual termination of the limey deposits, their number being in agreement with the age of the fish in years as estimated by Borodin. 4. On the presence in our collections of shad of increasing size possessing a proportionately increasing number of transverse grooves in their scales and possessing otoliths with proportionately increasing size and number of annuli. Shad whose scales and otoliths have been compared in this report are of the following ages : 1, 3, 4, 5, 6, 7, 8 and 10 years.

58 TABLE I. Growth of male shad and their otoliths ; ages based on number of transverse grooves in scales. Fish taken from April to July.

Mean Serial Total length Otolith Mean total otolith number of fish length length of fish length Age-1 year and 2 months 112 14.3 cm. 1.4 mm. 14.3 cm. 1.4 mm. Age-3 years 94 29.5 cm. 3.4 mm. 29.5 cm. 3.4 mm. Age-4 years 2 31.5 cm. 3.5 mm. 54 35.0 cm. 3.3 mm. 33.2 cm. 3.4 mm. Age-5 years 351 39.0 cm. 3.4 mm. 292 32.5 cm. 3.4 mm. 294 34.3 cm. 3.0 mm. 344 35.0 cm. 4.0 mm. 352 39.0 cm. 3.8 mm. 342 32.5 cm. 3.5 mm. 35.1 cm. 3.6 mm. Age-6 years 336 38.7 cm. 3.8 mm. 38.7 cm. 3.95 mm. 340 38.7 cm. 4.1 mm. Age-7 years 339 45 cm. 4.0 mm. 306 46 cm. 4.3 mm. 317 46 cm. 3.7 mm. 324 45 cm. 3.9 mm. 297 47 cm. 4.1 mm. 300 47.5 cm. 3.9 mm. 348 46.2 cm. 4.2 mm. 337 46.7 cm. 4.1 mm. 341 47.5 cm. 4.1 mm. 305 48.0 cm. 4.2 mm. 309 50.0 cm. 4.4 mm. 313 48.0 cm. 4.7 mm. 316 50.0 cm. 4.5 mm. 319 49.0 cm. 4.5 mm. 322 48.0 cm. 4.2 mm. 345 42.5 cm. 4.8 mm. 296 50.0 cm. 4.8 mm. 46.85 cm. 4.20 mm. Age-8 years 320 51.5 cm. 3.9 mm. 330 46.0 cm. 4.4 mm. 331 46.0 cm. 4.0 mm. 293 47.5 cm. 4.5 mm. 299 49.5 cm. 4.5 mm. 326 48.0 cm. 4.4 mm. 338 47.5 cm. 4.8 mm. 47.7 cm. 4.31 mm. 59

Mean Serial Total length Otolith Mean total otolith number of fish length length of fish length Age-9 years 346 46.2 cm. 4.3 mm. 343 45.0 cm. 5.1 mm. 334 50.0 cm. 4.8 mm. 46.9 cm. 4.61 mm. Growth of female shad and their otoliths-age based on number of transverse grooves in scales. Fish taken from April to July. Age-7 years 318 51.5 cm. 4.0 mm. 327 46.0 cm. 4.5 mm. 328 47.0 cm. 4.1 mm. 335 47.0 cm. 4.0 mm. 314 48.0 cm. 4.4 man. 325 50.0 cm. 4.2 nun. 303 50.0 cm. 4.3 mm. 347 46.2 cm. 4.8 mm. 47.3 cm. 4.24 mm. Age-8 years 302 . 52.0 cm. 4.6 mm. 312 52.0 cm. 4.5 mm. 315 52.0 cm. 4.5 nun. 321 50.0 cm. 4.4 mm. 51.0 cm. 4.45 mm. Age-9 years 323 51.0 cm. 4.3 mm. 310 55.0 cm. 5.1 mm. 329 53.0 cm. 5.2 mm. 332 48.0 cm. 4.3 mm. 51.5 cm. 4.65 mm.

60 PART IV.

REPORT ON HELMINTH PARASITES FROM THE SHAD.

By EDWIN LINTON

Medical Department University of Georgia, Augusta, Georgia. Ascaris adunca Rudolphi. Three vials in a collection sent to me by the Connecticut Department of Fish and Game, Hartford, Conn, contained round worms with labels as follows : 1. From stomach, of shad, Long Island Sound, May 6, 1924. 2. Round worms from stomach and intestine of shad, April 1, 1924. 3. Round worms from intestine of adult shad, N. C. April 1, 1924. There are in all 12 immature worms from 12 to 25 mm. in length and one adult measuring approximately 40 mm. in length. They evidently belong to the species recorded by Leidy as Ascaris adunca Rudolphi. (Journal Comp. Med. and Surg. vol. 9, pp. 211-217, Parasites of the shad and herring; re- printed in Smith. Miss. Coll., vol. 46, p. 220). The same form, also from the shad, was recorded by me in the Bulletin of the U. S. Fish Commission for 1899, 440, pl. 12, figs. 138, 139. The diameter is nearly uniform throughout the greater ,portion of the length ; the lateral membrane is very slightly developed ; the jaws are armed with four blunt teeth, arranged in pairs and each bears a single papilla ; the breadth of the dorsal jaw about equals the length. The esophagus is relatively long and cylindrical ; near its base there is a slight constriction which marks off a subglobular portion. From the base of the esophagus a diverticulum extends back beside the intestine and from the enterior end of the intestine a diverticulum extends forward beside the esophagus (Figure 1). These diverticula are of nearly equal length and each is somewhat less than half the length of the esophagus. In one specimen, about 15 mm. in length, the

61 length of the esophagus was 1.4 mm., the length of the esop- hageal diverticulum 0.56, and of the intestinal diverticulum 0.63. In another specimen, approximately 25 mm. in length, the esophagus measured 2.52, its diverticulum 0.84, and the diverticulum of the intestine 1.09.

EXPLANATION OF FIGURES. Fig. 1. Ascaris adunca Rudolphi. From stomach and intestine of shad. 1. Anterior end of immature worm. a, esophagus; b, diverticulum of intestine; c, diverticulum of esophagus. Length of esophagus 1.4 mm. 2. Ventral view of anterior end of immature worm. Diameter at base of jaws 0.24 mm. 3. Dorsal jaw of adult, dorsal view, teeth shown in optical section. Diameter 0.16 mm. 4. Outline of posterior end of adult male. Diameter at anal aperture 0.22 mm. Fig. 2. Scolex polymorphus Rudolphi from Shad. Optical section of a specimen mounted in balsam. a, bothrium; b, terminal sucker (myzorhynchus). Dimensions 0.56 by 0.42 min. The anal papillae were shown only in part in the one adult male in the collection. Behind the anal aperture and in front of it for a short distance, the cuticle had been damaged. About 18 preanal papillae could be seen on each side. These were smallish, of uniform size, and placed at equal distances from each other. The post-anal region is short, approximately equal to the diameter at the anal aper- ature, somewhat less than that in the adult male. Dimensions of adult male and of one of the immature worms. Length ...... 40.00 15.00 Diameter at base of jaws ...... 0.24 0.11 Length of jaws ...... 0.14 0.08 Diameter, middle ...... 0.84 0.28 Diameter at anal aperture ...... 0.22 0.12 Distance of anal aperture from posterior end - - - - 0.15 0.12 Larval Cestodes (Scolex polymorphus, Rudolphi) from shad. Four vials in the collection contain larval cestodes, a few of them, embedded in small pieces of liver appear to be slightly encysted. These larvae are subglobular or ellipsoidal and of nearly uniform size.- Two typical larvae measured 0.53 by 0.60 mm., and 0.49 by 0.63, mm. respectively. The scoleces were retracted in all cases. There can be but little doubt that these larval cestodes are identical with forms found by Leidy in the shad, and named by him Gymnoscolex picta (1. c., p. 220).

62 Fig. 1. Ascaris adunca Rudolphi; from stomach and intestine of shad.

Fig. 2. Scolex polymorphus from shad. These forms may be referred to that group of larval cestodes which is usually designated by the name Scolex polymorphus, which is a convenient name for characteristic ces- tode larvae, belonging to different species, found in the alimentary canal of a large number of marine fishes and in the cystic duct of a few, e.g, the squeteague and common flounder. The bothria, so far as they can be made out, are plain and about 0.15 mm. in diameter. There is a muscular anterior sucker or myzorhynchus, about 0.11 mm. in diameter. Cal- careous bodies are abundant in the parenchyma. The adult stages of these larvae are found in the spiral valve of sharks and skates.

Bibliography. Leim, A. H., 1924. The Life History of the Shad ( Alosa sapidissima Wilson) with Special Reference to the Factors Limiting its abundance. Contributions to Canadian Biology, N. S., vol. II. part I, 1924, University of Toronto Press. (Dr. Leim's paper includes a comprehensive bibliography of the shad). Rice, H. J., 1878. Notes on the development of the shad, Alosa sapidissima Maryland Commissioner of Fisheries Rep. 1878, p. 95-106, Pl. VI. Ryder, John A., 1881. The food of the young shad. (In: The protozoa and pro- tophytes considered as primary or indirect sources of food of fishes). Bull, U. S. Fish Commission, Vol I, 1881, p. 236- 251. •Ryder, John A., 1882. Observations on the absorption of the yelk, the food, feeding, and the development of embryo fishes, comprising some investigations conducted at the central hatchery, Armory Bldg., Washington, D. C. Bull, U. S. Fish Commission, Vol. 2, 1882, p. 179-205. Ryder, John A., 1885. Clupea sapidissima Wilson (The Common Shad) On the development of osseus fishes, including marine and fresh water forms). U. S. Commission of Fish and Fisheries. Commissioner's Rept., 1885, pp. 523-533, pls. 14-22.