The Canadian Fish Culturist

ISSUE TEN MAY, 1951

THE CANADIAN FISH CULTURIST

' lr L ..:.[.ES AND OCEA*$ BIBLIOTHÈQUE PÉCHFS ET 0 ^AN^^^'

Published at Ottawa by The Department of Fisheries of Canada CONTENTS

PAGE Fecundity of Quebec Lampreqs-VADIM D. VLADYKOV .... 1

A Splashless Tank for Transporting Fish-F. E. J. FRY ...... 15 Age and Growth of Lake Sturgeon from Lake St. Francis, St. Lawrence River. Report on Material Collected in 1947- JEAN-PAUL CUERRIER and GEORGE ROUSSOW ... . 17

"Red Sore" Disease of Pile in Mont Tremblant Park District, Quebec-LEO MARGOLIS ...... 30

On the Theory of Adding Nutrients to Lakes with the Object of Increasing Trout Production-F. R. HAYES ...... 32 Eaperimental Rearing of Yellow P"ilkeperch Fry in Natural Waters- W. B. SCOTT, D. N. OMAND and G. H. LAWLER.... 38

Further Observation upon the Movements of Speckled Trout in a Prince Edward Island Stream-M. W. SMITH ...... 44

Requests for earlier issues of The Canadian Fish Culturist continue to be received. A limited number of copies of issue No. 9, December 1950, remain on hand and distribution will be made on. request until the supply rune out. No copies of earlier issues are now available.

Published under Authority of HON. R. W. MAYHEW, M.P. Minister of Fisheries

I Fecundity of Quebec Lampreys"' by Vadim D. Vladykov Director of Biological Laboratory, Department of Fisheries, Zue.

The published data on the fecundity of lampreys are very scanty. There are only the odd observations on Petromyzon marinus by Surface (1899) and Gage (1928), and on Ichthyomyzon fossor by Leach (1940). The purpose of the present paper is to fill the gaps in our knowledge of this subject. As was mentioned in a previous paper (Vladykov, 1949), the following four species are found in Quebec waters: 1. American Brook Lamprey, Entosphenus lamottenii (Le Sueur) 1827, 2. Northern Brook Lamprey, Ichthyomyxon fossor Reighard & Cummins 1916, 3. Northern Lamprey, Ichthyomyzon unicuspis Hubbs & Trautman, 1937, and 4. Sea Lamprey, Petromyxon marinus Linnaeus 1758. The first two species are non-parasitic lampreys, while the remaining two are dangerous predators preying on a number of different fish species. For the list of victims of landlocked P. marinus(2) see Surface (1899) and Gage (1928), while the information on the anadromus form is summarized by Vladykov (1949), and Bigelow & Schroeder (1948). Hubbs & Trautman (1937) listed some species on which I. unicuspis feeds. For the present investigation 59 specimens, belonging to four species, have been studied. The great majority of lampreys came from Quebec (Table 1), while landlocked P. marinus were obtained from the Great Lakes. Mr. Matt Patterson kindly collected P. marinus from Hibbards Creek, a tributary of Lake Michigan, Wisconsin; while Mr. R. E. Whitfield obtained landlocked specimens from the Thessalon River, North Channel, Ontario. The author wishes to thank most cordially those persons for their help. Method of Determining Fecundity As eggs of lampreys are very small, the volumetric method(3) is not practical. The direct counting of the eggs is not very easy either on account of their size and high numbers. Therefore, the estimate of the eggs was made by weighing a sample of the ovary and then counting the eggs contained in it. The number thus obtained was multiplied by the weight of the whole ovary('). The procedure was as follows:

(1) Contribution No. 32 of the Department of Fisheries, Zuebec. (2) A resume of dangerous predation of landlocked P. marinus in the Great Lakes region during recent years is given by Vladykov (1949). Royce (1950) published an account on the number of scars made by P. marinus on Lake Trout (Cristivomer namaycush) in the Seneca Lake, New York. (') This method was employed with success for species with larger eggs, such as Leucichthys artedi (Stone, 1937), Salvelinus fontinalis (Vladykov & Legendre, 1940), etc. (') The same method was used already by Gage (1923, p. 169)., 78592-1 i Table 1 Details of material studied

Number Collecting data Species of specimens Date Locality Method of fishing Collector

E. lamottenii ...... May 5 '49 Veuillette R., Ste-Geneviéve•de•Batiscan, P.Q. dip net V. D. Vladykov

E. laniottenii ...... May 28 '48 Noire R., Pont•Rouge, P.Q. dip net V. D. Vladykov

I. fossor ...... May 8 and 22 '48 Yamaska R., St-Cksaire, P.Q. dip net V. D. Vladykov

1. unicuspis ...... 1944-49 St. Lawrence R., various localities, P.Q. fishing weir V. D. Vladykov

P. marinus ...... May 20 '49 St. Lawrence R., St•Vallier, P.Q. fishing weir V. D. Vladykov

P. marinus ...... June 2 '48 Little Thessalon R., Thessalon, Ontario dip net R. E. Whitfield

P. marinus ...... June 9-July 7 '48 Hibbards Creek, Jacksonport, Wisconsin lamprey trap Matt Patterson

(1) These specimens were caught in the Thessalon River, at Little Rapids, North Channel, between Lakes Superior and Huron. ($) These specimens were taken from traps set across Hibbards Creek, a tributary of Lake Michigan, about one mile north of Jacksonport, Door County, Wisconsin. 3 Table 2

Comparison of actual and estimated fecundities of I. fossor

Number Number Difference of eggs of eggs No. per cent counted evaluated

1 ...... 1,317 1,324 + 0-5

2 ...... 1,233 1,284 + 4•1

3 ...... 1,115 1,128 + 1-2

4 ...... :...... 1,374 1,416 + 2•3

5 ...... 1,336 1,278 - 4•3

6 ...... 1,824 1,820 - 0•2

7 ...... 1„979 1,960 - 1•0

8 ...... 1,824 1,740 - 4-6

9 ...... 1,711 1,626 - 5•0

Average ...... 1,524 1,508 -1•07

1. A specimen, after being preserved in 4-5 per cent formalin for a period varying from a few weeks to six years, was measured to the nearest millimeter, from the anterior tip of the disc to the extremity of the caudal fin, and accurately weighed. 2. The female lamprey was pinned with its right side next to the cork board. The incision was made on the left side to expose the ovary. 3. The dimensions of the ovary in situ were taken and then the ovary was removed.(') 4. The ovary, after being placed on cheese cloth to remove excess moisture, was weighed very accurately on a Torsion balance. 5. A portion of the ovary was removed and weighed. It is preferable to have a sample weighing exactly one gram. 6. The eggs contained in this sample' were separated by means of two dissecting needles, one straight and the other hooked, and then counted in a glass dish placed over a black back-ground.(2) 7. The total number of eggs in the ovary was evaluated by multiplying the number of eggs in a one gram sample by the total weight of the ovary. 8. The diameter of 20 eggs was measured to the nearest 0.5 millimeter by placing the eggs in a row on a measuring board, made in a form of a trough with a triangular cross-section.

(1) There is only a single ovary in lampreys. (_) The deurmination of the number of eggs were made with great care by Michael T. H. Brodeur. summer assistant. 78592-1 } Table 3 Comparison of actual and estimated fecundities of E. lamottenii

Number Number Difference of eggs No.(') of eggs per cent counted evaluated

2 ...... 3,648 3,484 - 4•5

3 ...... 2,907 2,920 + 0•4

4 ...... 3,067 3,158 + 3•0

5 ...... 1,085 1,052 - 3•0

6 ...... 1,568 1,600 + 2•0

7 ...... 1,728 1,780 + 3•0

8 ...... 2,191 2,234 + 2•0

9 ...... 2,372 2,274 - 4•1

10 ...... 2,371 2,360 - 0•5

Average ...... 2,326 2,318 -0-36

(1) Specimen No. 1 (see Table 4) was excluded from this table, as the number of evaluated eggs in its case differed by 19 per cent from the counted number of eggs, no doubt due to a faulty manipulation.

The described method, although rather tedious as a gram of ovary contains at least 1,000 eggs, is sufficiently accurate to give a clear picture of the fecundity of lampreys. A comparison of actual and estimated fecundities in the case of two species is given in Tables 2 and 3. The maximum difference was not greater than 5 per cent. It should be borne in mind that lampreys spawn only once in their life-span, hence all or at least the greatest majority of oocytes ("primary ova") are developing into mature eggs, all of which are of the same size. In other words, the weight of the ovary consists principally of the weight of the eggs, while the connective tissue and other ovarian elements account for a very negligible part. Stages of Maturity In the case of female lampreys the degree of maturity can be determined first of all by the dimensions of their unshed eggs, which during the spawning season in Quebec species vary from 0.8 millimeters (in I. unicuspis) to 1.2 millimeters (in I. fossor). How- ever, there are several other characteristics interior and exterior which help to classify females according to their sexual development. These characters are as follows: 1. In mature females the anal fin-like fold is well-developed, and the tail turns typically upwards, while in breeding males it bends downwards. 2. The lumen of the intestinal tract(') reduces progressively, becoming non- functional and closed in fully mature individuals of all lamprey species. Moreover,

(t) In our Tables 49, the width of the intestine was measured immediately behind the posterior end of the liver.

_L 5

the liver acquires a green colour, due to probably the diffusion of the bile. Thus the smaller the width of the intestine, the more mature is the lamprey of either sex.

Table 4 Actual fecundities of E. lamottcnii

Lamprey Ovary Diameter Width of No. weight Number of I egg intestine Maturity Length Weight of eggs indea (g.) (mm.) (mm.). (mm.) (g.)

1 116 3-1 0-6 1,085 0-93 1•0 19-4

2 118 3-8 0•5 1,568 0-83 3-0 13-2

3 128 3-0 0•9 1,728 0•95 0-5 30-0

4 138 4-0 1•0 2,191 0•88 3•0 25-0

5 149 5•4 1-2 2,372 0-95 1-5 22-2

6 152 5•5 1-4 2,371 0-80 3-0 25-4

7 154 5•6 1-0 2,451 0-88 1-0 17-9

8 156 7-0 1•2 3,648 0•90 0-5 17-2 9 156 7•7 1-3 2,907 0-90 2-0 16-9

10 158 7-0 1-3 3,067 0•90 2-0 18-6

Average 142-5 5-2 1-04 2,339 0•89 1-75 20•0

Table 5 Actual fecundities of I. fossor

Lamprey Ovary Diameter Width of Numberer Maturity No. weight of 1 egg intestine Length Weight eggs index (g.) (mm.) (mm.) (mm.) (g.)

1 128 3-8 1•2 1,317 0-95 0-1 31-6

2 131 3-0 1-4 1,233 1-10 0-2 46-6

3 133 3-6 1•0 1,115 0•98 0-1 27-7 4 133 4-1 1-2 1,374 1•20 0•1 29-2

5 134 4-2 1-5 1,336 1-05 0-2 35-7

6 139 4-6 1-7 1,824 1•05 0-2 37-0

7 144 5•5 1-7 1,979 1-20 0•2 30-9

8 146 4-7 1-4 1,824 0•98 0•1 29•8

9 150 5•2 1•8 1,711 1-05 0•2 34-6

Average 137•6 4-3 1-43 1,524 1•01 0-14 33-2

-L CM Table 6 Estimated fecundities of I. unicuspis

Lamprey Ovary Diameter Width of Locality Number aturity No. Date weight of 1 egg intestine (Quebec) Length Weight of eggs index (g.) (mm.) (mm.) (mm.) (g•)

1 Neuville ...... Apri121'47 201 13•5 4•6 15,474 0•80 2•0 33•0

2 Neuville ...... '...... Oct. 5 '45 204 21•9 1.2 17,848 0-45 5-5 5.5 3 Gentilly ...... Jan. 18 '49 217 41•9 4•6 15,134 0•70 13•0 11.0

4 , Ste-Pétronille ...... Apri124 '48 246 356 3-4 15,443 0-70 8-0 9-6 5 Montmorency ...... May 9'48 251 37•5 5•3 14,310 0•85 4•0 14•1

6 Berthier-en-bas ...... Oct. 6 '46 262 54-6 3-4 18,795 0.60 7.5 6.2

7 Nicolet . . . . _ ...... Oct. 10 '45 270 46-5 6-o 12,006 0.80 7-0 12-9 8 St-Romuald ...... Nov. 10 '44 287 56-6 8-6 25,310 0.80 6-0 15.2 9 St-Vallier ...... Sept. 26 '44 300 75•0 4•3 29,412 0-60 9•5 5•7

10 Neuville ...... :...... Sept. 16'46 312 68•1 7•9 26,386 0•70 8-5 11•6

Average St. Lawrence River ...... 1944-49 255 45•1 4•93 19,012 0•70 7•10 10•9 7

3. From the time of reaching the peak of physical development, which in Quebec corresponds to the period November-January, to spawning in the spring the length and weight of adult lampreys of both sexes progressively diminish. Thus at spawning time sexually mature individuals are much smaller than they were a few months previous. In the extreme case of a spawning I. unicuspis, the shrinkage in length was up to 22 per cent and loss of weight to 57 per cent in comparison with the measurements made on the same specimen in November, that is six months before (Vladykov and Roy, 1948). On account of this shrinkage the extent of which varies with the individual, it is often very difficult to establish a correlation between the number of eggs and the size of a female.

4. To define the degree of maturity, the weight of the ovary in grams was expressed in percentage of the total weight in grams of a female, and is called "maturity index". Thus the higher the index, the higher is the degree of maturity. In all our species, during spawning this index is equal to at least 30, with a maximum of 47.

Fecundity in Different Species In the case of E. lamottenii (Table 4) and I. fossor (Table 5) the number of eggs were actually counted, while in the remaining species (Tables 6-9) it was evaluated. E. lamottenii.-The data on the absolute fecundity of ten specimens from Quebec are given in Table 4. The length of these females varied from 116 to 158 millimeters, with an average of 143 millimeters, and average weight of 5.2 grams. All these lampreys were taken at the spawning season, thus there was very little variation in the diameter of the eggs, the range being 0.80-0.95 millimeters and an average of 0.89 millimeters.

The number of eggs varied from 1,085 to 3,648, with an average of 2,339. There is a definite correlation between the size of the specimen and the number of eggs. In the case of the three smallest females (116-128 mm.) the number of eggs is less than 2,000. In a group of an intermediate size (138-154 mm.) the number of eggs was more than 2,000 but less than 2,500. In the three largest lampreys (156-158 mm.) the variation was from 2,900 to 3,650. Published records on the number of eggs in E. lamottenii are very limited: Gage (1928, p. 169) gave for a New York specimen 3,276 eggs; Dean & Sumner (1898) estimated from a gravid female taken at the spawning time that she contained 860 eggs. It seems almost certain that a part of her eggs had already been laid. The maturity index in our specimens varied from 17 to 30, the average being 20. The individual (No. 3) with the highest index was a female in the most advanced stage of maturity: the diameter of the eggs was 0.95 millimeters, and the width of the intestine was only 0.5 millimeter.

1. fossor.-The data on the fecundity of nine Quebec specimens are given in Table 5. The lengths varied from 128 to 150 millimeters, with an average of 138 millimeters and an average weight of 4.3 grams. These specimens were collected during the spawning season, thus showed large eggs with the diameter varying from 0.95 to 1.05 millimeters, with an average of 1.01 millimeters. 8 Table 7 Estimated fecunditiea of landlocked P. marinus from Ontario

Lamprey Ovary Diameter Width of Number Maturity No. weight of eggs of 1 egg intestine Length Weight index (g•) (mm.) (mm.) (mm.) (g.)

1 330 81•1 16•7 28,891 0•90 3•0 20•6

2 353 100•4 19•2 39,490 0•80 2•5 19•2

3 359 109•2 22•7 52,437 0•85 2•0 20•8

4 368 112•0 24•0 53,520 0•85 3•0 21•4 5 377 129•7 26•5 62,924 0•83 2•5 20•5

6 390 130•6 28•8 65,280 0•85 4•0 22•0

7 396 143•6 30•2 50,343 0•95 3•0 20•9

8 409 153•7 27•6 74,023 0•80 3•5 18•0

9 418 175•3 40•6 66,709 0•90 2•0 23•2 10 435 221•0 34•3 65,513 0•85 4•0 15•6

Average 383•5 135•7 27•06 55,913 0•86 2•95 20•0

Table 8 Estimated fecundities of landlocked P. marinus from Wisconsin

Lamprey Ovary Diameter Width of Number Maturity No. weight of 1 egg intestine Length Weight of eggs index (g.) (mm.) (mm.) (mm.) (g-)

1 201 65•2 19•7 58,485 0•80 3•0 30•2

2 310 59•0 14•0 40,838 0•75 2•5 23•7 3 313 61•8 14•7 49,686 0•75 5•0 23•8

4 326 101•0 23•3 38,678 0•88 5•0 23•0

5 343 97•2 19•0 45,410 0•80 5•0 19•6 6 366 167•0 55•0 77,440 1•00 1.0 33•0

7 372 169•1 47•1 72,110 0•90 2•5 27•9

8 410 184•6 47•5 79,420 0•95 4•5 25•8

9 423 208•5 51•9 85,712 0•90 3•5 24•8 10 439 158,5 28•0 80,920 0•80 9•0 17•7

Average 359•3 127•2 32•01 62,870 0•85 4•1, 25•1 9

The number of eggs ranged from 1,115 to 1,979, the average being 1,524. The correlation between the size and number of eggs is noticeable to a certain degree. In the case of lampreys ranging from 128 to 134 millimeters, the number of eggs was less than 1,500, while in larger females (139-150 mm.) this number was from 1,700 to nearly 2,000. Leach (1940, p. 32) counted the eggs in three I. fossor from Indiana. Specimens with lengths of 92, 113, and 122 millimeters showed the numbers of eggs to be 780, 1,050 and 1,340 respectively. The maturity index in our material was very high, from 28 to 47, with an average of 33, as all females were collected on the spawning ground. 1. unicuspis.-Specimens were taken in the St. Lawrence River, Quebec, from eight different localities throughout the six-year period, 1944-49 (Table 6). These lampreys were caught in different months of the year from January to November. The lengths ranged from 201 to 312 millimeters, with an average of 255 millimeters, and an average weight of 45 grams. The diameter of the eggs varied considerably from 0.45 to 0.85 millimeters, with an average of 0.73 millimeters. The number of eggs was evaluated to be from 12,006 to 29,412, with an average of 19,012 eggs. The correlation between the size of lamprey and number of eggs is evident only in specimens arranged in large length-classes. In individuals from 201 to 270 millimeters the number of eggs was smaller than 20,000, while in larger females (287-312 mm.) this number varied from 25,000 to nearly 30,000. As our specimens were collected in different months, their indices of maturity showed an unusually large range from about 6 to 33, with an average of 11. From Table 6 it is evident that only specimen No. 1 was ready to spawn, while the remaining were immature females. Table 9 Estimated fecundities of anadromous P. marinua from Quebec

Lamprey Ovary Diameter Width of Number Maturity No. Length Weight weight 1 egg intestine ofo eggsg index (mm.) (g.) (g.) ^ (mm.) (mm.)

1 666 560 73•8 142,139 0•90 10-0 13•1

2 698 600 78-9 123,873 0•90 6•0 13-2 3 722 680 92-6. 136,122 0-95 6•0 13•6

4 742 925 122•6 202,413 0-95 7-0 13-2

5 750 870 127-9 187,757 0-95 7-0 14-7 6 750 905 107-9 166,245 0•90 13-0 11-9

7 751 875 110-3 137,875 0-95 10•0 ' 12-6

8 753 1,000 116-4 258,874 0-90 12•0 11-6

9 766 860 102-0 128,724 1-05 5.0 11•8

10 841 1,145 146-2 231,873 0-95 12•0 12-8

Average 742-9 842•0 107•86 171,589 6 0-94 8•80 12-8

78592-2 10

P. marinus.-In the Province of Quebec there is commonly found only the anadromous form of P. marinus (Vladykov, 1949). In order to complete our studies, we obtained samples of the landlocked form from North Channel, Ontario, and Lake Michigan, Wisconsin. Tables 7-9 summarize the data on fecundities of different forms of P. marinus.

800

^ eggs q length 600

H M C v U) 400 o ^ c

^.. tu.

200

U. E.I.

0 a Figure 1

Correlation between the average length of female lamprey of four different species and the average number of eggs. The data for landlocked P. marinus are those for Ontario specimens. il

The landlocked form from Ontario was collected in the Thessalon River, at Little Rapids, on June 2, 1948. These specimens were well advanced in maturity, but were not ready to spawn as yet (Table 7). Their lengths were from 330 to 437 millimeters, with an average of 384 millimeters and an average weight of 136 grams. The diameter of eggs varied from 0.80 to 0.95 millimeters, with an average of 0.86 millimeters. The number of eggs were evaluated to be from 28,891 to 74,023, with an average of 55,913. Only two of the smallest females (330-353 mm.) had less than 40,000 eggs, while the remaining (359-435 mm.) possessed between 50,000 and 75;000 eggs. The maturity index varied from 16 to 22, with an average of 20. The specimens from Wisconsin (Table 8) were somewhat smaller, from 291 to 439 millimeters, with an average of 359 millimeters, and an average weight of 127 grams. As this sample was collected from June 9 to July 7, 1948, there was observed a pronounced variation in the diameter of the eggs, ranging from 0.75 to 1 millimeter, with an average of 0.85 millimeters. The extremes in the number of the eggs were found to be from 38,678 to 85,712, with an average of 62;870. This number is considerably higher than that found in North Channel specimens. Apparently Lake Michigan specimens display a higher fecundity. The correlation between the size of the female and the number of eggs is shown only in a broad range of length-classes. For instance, among smaller individuals (291-343 mm.) the number of eggs is less than 60,000, while in larger ones (366-439 mm.) it varies from 72,000 to 86,000. The maturity index was from 18 to 33, with an average of 25. Gage (1928, p. 169) for three landlocked P. marinus from Cayuga Lake, New York, listed 63,000, 65,000 and 108,270 eggs. He considered that the two lampreys with the smaller numbers of eggs apparently had already laid a part of their eggs, as they were taken from the spawning beds. Our studies showed that these smaller numbers were directly comparable with those obtained for Ontario and Wisconsin, while 108,270 eggs were never duplicated in our material. Carl L. Hubbs in an unusually large specimen of landlocked P. marinus (204 inches) counted 78,762 eggs, (') a number repeated among our Wisconsin specimens. On the other hand, it was rather astonish- ing to read in Surface (1899, p. 200), that "adult female lake lampreys lay between 25,000 and 30,000 eggs, according to size, the average being about 27,500". The anadromous specimens from Quebec ranged in length from 660 to 841 millimeters, with an average of 743 millimeters, and an average weight of 842 grams (Table 9). This sample showed very little variation in the diameter of eggs, which was from 0.90 to 1.05 millimeters, with an average of 0.94 millimeters. The estimated numbzr of eggs ranged from 123,873 to 258,874, with,an average of 171,589. Our findings are directly comparable with 235,950 eggs, a number counted by-Gage (1928, p. 169) in a specimen of anadromous P. marinus from Lawrence, Massachusetts.('). It should be noted that in Quebec specimens we were unable to establish any correlation between the size of Sea lamprey and the number of eggs. The index of maturity varied from about 12 to 15, with an average of nearly 13.

0) This observation by Hubbs was quoted by both Schneberger (1947, p. 12) and Applegate (1947, p. 7). (') This observation by Gage was quoted also by Dees (1950). 78592-2+j Table 10

Comparison between absolute fecundities of different species

Lamprey Ovary Number Maturity Index Species of Length in Weight in Diameter of Number of millimeters grams specimens 1 egg in mm. eggs Range Average Range Average Range Average Range Average Range Average

1. fossor ...... 9 128-150 138 3•0-5•S 4•3 27•7-46•6 33•2 0•95-1•05 1•01 1.,115-1,979 1,524

E. lamottenii ...... 10 116-158 143 3•1-7•7 5•2 13•2-30•0 20-0- 0-8Ô-0•95 0•89 1;085-3,648 2,339

1. unicuspis ...... 10 201-312 255 13•5-75•0 45•1 5•5-33•0 10.9 0•45-0•85 0•70 12,006-29,412 19,012

P. marinus(1) ...... 10 291-439 359 59•0-208•5 127•2 17•7-33•0 25•1 0•75-1•00 0•85 38,678-85,712 62,870

P. marinus(2) ...... 10 330-435 384 81•1-221•0 135•7 15•6-23•2 20•0 0•80-0•95 0•86 28,891-74,023 55,913

P. marinus(') ...... 10 666-841 743 560-1,145 842•0 11•6-14•7 12•8 0•90-1•50 0•94 123,873-258,874 171,589

(1) Landlocked from Lake Michigan, Wisconsin. (2) Landlocked from North Channel, Ontario. (') Anadromous from the St. Lawrence River, Quebec. 13

Table 11 Relative fecundities of different lamprey species

Maturity Species Diameter of Number of index 1 egg (mm.) eggs in 1 gram

1. fossor ...... 33•2 1•01 1,066

P. marinus (1) ...... 12.8 0.94 1,595

P. marinus (_) ...... 20•0 0•86 2,088

P. marinus (s) ...... 25-1 0•85 2,242

E. lamottenii ...... 20•0 0•89 2,249

I. unicuspis (')...... 11•2 0.73 3,839

(') Anadromous from the St. Lawrence, River, Quebec.. (2) Landlocked from North Channel, Ontario. (') Landlocked from Lake Michigan, Wisconsin. (') Specimen No. 2 (see Table 6) was excluded from data in this table.

Comparison between Absolute and Relative Fecundities In Table 10 we have arranged the species of lampreys in order of their increasing size. These data are graphically represented in Figure 1. It appears that the average number of eggs follows quite closely the average size of female of different species. In order of magnitude, the species are placed as follows: I. fossor, E. lamottenii, I. unicuspis, landlocked P. marinus, and anadromous P. marinus. Thus I. fossor lays the smallest number of eggs, while anadromous P. mari-nus is the most prolific. There is another way to treat the problem of fecundity, that is, to consider how many eggs are contained in a gram of ovary of different species. This approach can be called the "relative fecundity". The number of eggs in a gram of ovary depends mainly on the size (diameter) of the eggs. In Table 11, which presents these data, there is a minor discrepancy in the case of E. lamottenii. Although the average diameter of eggs in this species was larger (0.89 mm.) than in landlocked P. marinus (0.85-0.86 mm.), the number of eggs in E. lamottenii was somewhat higher (2,249) than in the landlocked form (2,242 or 2,088). This was caused probably by the fact, that the number of eggs in E. Iamottenii was counted while in the other it was evaluated. From the point of view of relative fecundity, in order of increasing numbers of eggs, the species are arranged as follows: I. fossor, anadromous P. marinus, landlocked P. marinus, E. lamottenii, and I. unicuspis. Thus I. fossor again occupies the lowest position, while this time the most prolific is I. unicuspis. In Table 11 we excluded specimen No. 2 of I. unicuspis (see Table 6), which had rather numerous eggs (17,848) but of a very small diameter (0.45 mm.). If, however, this female should be included then the number of eggs in one gram of ovary of I. unicuspis would be raised to 4,528. From the relative fecundity viewpoint, P. marinus occupies a place next after 1. fossor. Among landlocked and anadromous forips of P. marinus there is also a pronounced difference, the former is much more prolific than the latter. 14

In conclusion we can repeat that both forms of P. marinus are very prolific from the absolute fecundity point of view. This fact explains clearly why P. marinus, particularly its landlocked form, can become so abundant in lakes where it becomes established. This is particularly true in the case of new habitats, such as the Great Lakes. Literature Cited

APPLEGATE, V. C. 1947. The menace of the Sea lampiey. Mich. Conservation, Vol.16,1947, No. 4: 6-10. Lansing, Mich. BIGELOW, H. B. and W. C. SCHROEDER. 1948. Cyclostomes. Fishes of the Western North Atlantic, Part 1, No. 1: 29-58. Memoir Sears Foundation for Marine Research, 1948. New Haven, Conn. DEAN, B. and F.B. SUMNER. 1898. Notes on the spawning habits of the Brook lamprey (Patromyzon wilderi). N.Y. Acad. Sci., Vol. 16: 321-324. New York. DEES, L. T. 1950. Sea lampreys of the Atlantic coast and Great Lakes. U.S. Fish and Wildlife Serv. Fishery Lea9et 360: 4 pp. Washington, D.C. GAGE, S. H. 1928. The lampreys of New York state-life history and economics. A Biological Survey of the Oswego River system. Suppl. Ann. Rept. N.Y. St. Cons. Dept., No. 17, 1927: 158-191. Albany, N.Y. HUBBS, C. L. and M. B. TRAUTMAN, 1937. A revision of the lamprey genus Ichthyomyzon. Mise. Pub. No. 35, Mus. Zool. Univ. Mich., 109 pp. Ann Arbor, Mich. LEACH, W. J. 1940. Occurrence and life history of the Northern Brook lamprey, Ichthyomyzon fossor, in Indiana. Copeia, No. 1: 21•34. ROYCE, W. F. 1950. The effect of lamprey attacks upon lake trout in Seneca lake, New York. Trans. Amer. Fish. Soc., Vol. 79: 71-76. SCHNEBERGER, E. 1947. The Sea lamprey-a menace to the Great Lakes Fisheries. Wis. Cons. Bull., Vol. 12, No. 1: 12-14. Madison, Wis. STONE, U. B. 1937. Growth, habits, and fecundity of the ciscoes of bondequoit Bay, New York. Trans. Amer. Fish. Soc., Vol. 67: 234-245. SURFACE, H. A. 1899. Removal of lampreys from the interior waters of New Tork. 4th Ann. Rep. Comm. Fish. Game and Forests, N.Y., 1898: 191-245. New York. VLADYKOV, V. D. 1949. kuebec lampreys (Petromyzonidae). 1.-List of species and their economical importance. Contr. Dept. of Fish., Quebec: 67 pp. Quebec. VLADYKOV, V. D. and V. LEGENDRE. 1940. The determination of the number of eggs in ovaries of Brook trout (Salvelinus fontinalis). Copeia, No. 4: 218-220. VLADYKOV, V. D. and J. M. ROY. 1948. Biologie de la lamproie d'eau douce (Ichthyomyzon unicuspis) après la métamorphose. (Résumé). Revue Can. Biol., Vol. 7, No. 3: 483-485. Montréal. 15

A Splashless Tank for Transporting Fish by

F. E. J. Fry Ontario Fisheries Research Laboratory Dept. of Zoology, University of Toronto

On long trips fish may be considerably battered when transported in the usua open tanks. Such injury can largely be prevented if the fish are carried in a closed container completely filled with water. Water tight closure of the top, however, presents a number of problems. The tank described below overcomes these difficulties by virtue of a pneumatic gasket which provides a very simple closure and allows the entire top to be taken off. The gasket itself, moreover, is a standard article, an ordinary 28" x 11" bicycle inner tube.

The tank is illustrated in Figure 1. It is made of 20-gauge galvanized iron rein, forced top and bottom with band iron. The tank at present in use measures 22" x 24' with the corners rounded to a 62" radius. Its overall height is 17". Approximately one inch of this is taken up by a plywood bottom giving a depth inside of 16". A ledge of 1" x 1" angle as indicated is provided 6" below the top, this ledge is soldered to the walls of the tank to give a water tight joint. The lid is 21" x 23" also of 20- gauge galvanized iron and has the corners rounded to a six-inch radius. The lid is a flat pyramid with a vertical rim approximately one inch deep. The edge is rein- forced by a :'I" rod. There is a one-inch tube about 4 inches long projecting up from the centre of the lid. A one hole stopper can be inserted in this hole during transit to further minimize splash. The tank is fitted with a suitable porous aerator through which air or oxygen may be diffused.

The tank is partially filled with water and the fish are introduced. Further water is then added to bring the level up to the base of the ledge. The lid is then laid loosely on the ledge and the deflated bicycle tube introduced between the vertical rim of the lid and the wall of the tank, the valve stem being allowed to project outside the tank through a suitable hole drilled in the tank just above where the ledge is soldered to the wall. After the tube is in place it is inflated with a few pounds of air, the amount being determined by experience. The inflated tube both makes a seal and holds the lid firmly in place. Sufficient water to completely fill the space under the lid is then added through the one-inch tube. The hole for the valve stem is drilled on one of the rounded corners which gives the stem a measure of protection. The nipples for the gas inlet and drain are similarly placed.

If the fish require cold water, the space above the lid is used as a tray for crushed ice.

6 Figure 1.

A Splashless Tank for Transporting Fish 17

Age and Growth of Lake Sturgeon from Lake St. Francis, St. Lawrence River. Report on Material Collected in 1947 by

Jean-Paul Cuerrier and George Roussow(') Institute of General Biology and Zoology, University of Montreal, Due.

In order to remedy a lack of knowledge of one of the most important fish of our freshwater commercial fisheries of the St. Lawrence River, and as a sequel to manuscript reports and memoirs submitted to various authorities (Cuerrier 1945a, 1946), the Provincial Department of Trade and Commerce, Quebec, provided facilities in 1947 to carry on intensive research on the sturgeon of the St. Lawrence and Ottawa Rivers. Some investigation had already been undertaken in Lake St. Peter during the course of the preceding years (Cuerrier 1945a, 1945b). The proposed programme undertaken in 1947 was designed to determine the economic value of the sturgeon, to make an inventory of the methods and areas of the fishery, and to study the principal aspects of the biology of the sturgeon, such as growth, feeding habits, migration and reproduction. This information could in turn provide the necessary data for improvement in the regulations governing fishing operations for this species in Quebec waters. The organization and execution of the programme were undertaken by jean-Paul Cuerrier, under the immediate direction of Dr. Georges Préfontaine, then director of the Institute of General Biology and Zoology, University of Montreal. The present report(*) summarizes the data collected in Lake St. Francis during 1947. It is a study of the sturgeon fishery of Lake St. Francis, and outlines information obtained on the growth, the length-weight relationship, and the state of maturity of the sturgeon from this region. Results of the tagging operations carried on in Lake St. Francis during.1947 are not discussed in this paper.

Material Collected With the collaboration of two fishermen of Sainte-Barbe, Huntingdon County, we were able to weigh and measure almost all the sturgeon caught by them in Lake St. Francis during the season of 1947, from June 21 to October 28. Many of the field observations and data were collected by G. Roussow and an assistant. The two fishermen whose catches we examined used nets of 32-inch-square mesh most of the time. The number of nets used varied between four and six, each measuring about 150 feet in length. The area fished by these men was nearly always the same, in the neighbourhood of the main channel, in front of Saint-Zotique and Sainte-Barbe.

(1) Mr. Cuerrier is now chief limnologist with the Canadian Wildlife Service, Department of Resources and Development, Ottawa, while Mr. Roussow is now with the Provincial Biological Bureau, !Zuebec.) (*) This paper is a translation of a report submitted to the Depaitment of Trade and Commerce, Zuebec, in Match 1949. The manuscript has been revised for publication. 78592-3 18

The total number of sturgeon examined was 342. Of these, 138 were killed, and sold for the most part on the local market, because they were of a weight lower than the requirements of the foreign market. The others, numbering 204, were tagged with a monel metal ring, and released at the same place.

Measurements and Weights The length of the specimens was taken, either in millimetres or in inches, with the aid of a measuring board, on which the fish was laid on its side, or with the aid of a metal tape graduated in inches extended above the specimen. The accuracy of the length measurements was of the order of a half-centimetre or a quarter-inch. In this report we refer only to the fork length, taken from the anterior tip of the snout to the posterior end of the shortest rays of the caudal fin. The conversion factor Y used to cônvert total length to fork length was 0.9166 (average factor obtained from an analysis of data collected from Lake St. Peter in 1945, unpublished). The sturgeon were weighed with the aid of a beam balance graduated in ounces, the capacity of which could be increased to 40 pounds by the addition of weights. Generally sturgeon were kept in wooden tanks for several days; they were measured and weighed at the time of sale; in the case of tagged fish, the captivity rarely exceeded three days. The data on weights therefore are slightly less than normal.

The Sturgeon Fishery in Lake St. Francis According to Fishery Statistics published annually by the Federal Department of Trade and Commerce, Ottawa, Lake St. Francis has figured as one of the regions of the St. Lawrence River where the sturgeon fishery has been among the most prosperous. These statistics show that from 1923 to 1933, the fishermen of Huntingdon County reported an annual catch of sturgeon varying between 14,000 and 35,400 pounds with an average of 27,040 pounds; from 1933 to 1943(1) the average annual catch was 13,820 pounds. Owing to the progressive decline in the catch, a great many of the riparian inhabi- tants have abandoned the sturgeon fishery even though the price paid to fishermen has more than doubled during the course of the last ten years. In the village of Saint- Anicet, for example, where a decade ago there was an important group of fishermen, there are now only a few fishermen, no longer professional but occasional. This decline in the yield of the sturgeon fishery in Lake St. Francis, associated with a decline in fishery effort, might be attributed to several causes; but according to the fishermen of the area, the only responsible factor is the erection of dams across the St. Lawrence River at Les Cèdres, at Saint-Timothée and at Coteau Landing, which have interfered with the migratory movements of the sturgeon. Without wishing to deny the extent of the repercussions of the dams on the biological conditions of Lake St. Francis and on its fish populations, one may ask whether the fishery methods in use in Lake St. Francis, as elsewhere, would not be equally responsible for the decline that is manifested in this region and in the waters of all the St. Lawrence River in general.

(') The year 1939 was excluded. because for that year a catch of 50,000 was indicated, while for the years preceding and following, the catch was 15,000 and 20,000 pounds. These 1939 figures seem open to question. 19 .

Regulations of the Sturgeon Fishery

Fishing permits for sturgeon in Lake St. Francis authorize only the use of a set line with bait. However, most of the fishermen use mainly a net with mesh of three and one-half to four inches square (seven to eight inches stretched). The fishing regulations of the Province of Quebec set the legal length of sturgeon taken in the St. Lawrence River at 28 inches, and oblige the fishermen to liberate any sturgeon of a smaller size. The text of the regulations, C.P. 5356, Art. 26, par.4, does not specify, however, whether it refers to the total length or the fork length:

"No sturgeon less than thirty-six inches in length shall be retained or kept out of the water, except in the St. Lawrence where the minimum length of sturgeon caught and retained shall be twenty-eight inches, and anyone who may accidentally take any sturgeon of less lengths than provided for herein shall immediately return such fish to the water, if possible uninjured."

According to Mr. Charles Frémont, General Superintendent, Department of Game and Fisheries, Quebec, the law is interpreted as referring to the fork length. If the Ontario regulations regarding sturgeon fishery in the southwest section of Lake St. Francis are examined, it is found that the minimum legal length, based on the fork length, is 36 inches; the same is true for the Ontario section of the Ottawa River. Elsewhere in Ontario, the legal length is 42 inches (The Game and Fisheries Act, Special Fisheries Regulations for the Province of Ontario, P.C. 5694, Art. 35, par. 1). The mesh of gill nets used for the sturgeon fishery in Ontario must be not less than 20 inches extension measure (op. cit., art. 57, par. 1), and, under special permit, 10 inches extension measure in waters other than the Great Lakes (op. cit., art. 57, par. 2).

Nets used by fishermen of Lake St. Francis, on the Quebec side, do not appear to offer any protection for small sturgeon. Convincing evidence is found in Figures 1 and 2, where have been recorded by polygons the length and the weight frequencies of sturgeon captured by the two fishermen in our service during the period mentioned. These data indicate that the fork length ranged between 16 and 50 inches and the weight between 0.75 pound and 42 pounds, but most of the fish measured between 22 and 32 inches, and weighed between two and.eight pounds. The mode of the length distribution is between 27 and 28 inches and that of the weight between four and five pounds. In cumulative percentage, 39.0 per cent of the sturgeon caught measured less than 28 inches, and 82.7 per cent less than 36 inches. The data also show that 65.2 per cent of the individuals weighed less than eight pounds and 82.7 per cent less than 12 pounds. It is evident, therefore, that a large number of sturgeop of a length in the neighbourhood of the minimum legal length are stopped and held by nets of mesh of three and one-half to four inches square.

It is impossible at the moment to state that the same picture is repeated every year and that it characterizes the general harvest of the sturgeon fishery in Lake St. Francis; we know that during spring and late autumn numbers of large-size sturgeon are captured, particularly at the head of the lake whére the fishermen of Cazavillo lay 7R.592-3} 35

> 0 20 z

LL O 15

0 0 1 1 I I I I I I1 I I I I ^ I I 1 I ^ I II I I I 1 I I ^ 1 1 I I I 1 I 15 20 I I 25 30 35 40 45 50

FORK LENGTH IN INCHES

Figure 1 Length frequency distribution of lake sturgeon caught in Lake St. Francis during 1947 50 15*4

IO%

I I I I i ^ I . iI i i 0 i I IIIII I I I I I I I I I 1. -I I 10 15 20 25 30 35 40 -WEIGHT IN POUNDS

Figure 2 Weight frequency distribution of lake sturgeon caught in Lake St. Francis during 1947 22

their set lines. Consequently the fishermen of the region would be desirous of obtaining fishing permits for the month of May, because, they say, sturgeon of the weight sought by the export market could be caught in large numbers during this period. To study this question, which raises the problem of the closed season for the sturgeon fishery, a series of observations were made during the spring of 1948 and will be developed in a future report.

Age Determination and Growth Study To determine the age of fish, one usually examines their scales; but if the scales are lacking, or are too small, or do not clearly show the summer and winter growth lines, one may have to examine certain bones, most generally the otoliths, which are contained in the internal ear sacs. This latter method was used by Harkness (1923) and Greely (1937) for age détermination and growth study of different species of sturgeon: Acipenser fulvescens, Acipenser brevirostris, and Acipenser oxyrhynchus. In a brief review of the methods used for age determination among sturgeon, Chugunov (1925)(1) recalled the work of V. Kler, published in 1916, on the use of bony rays of the pectoral fins and the plates of the caudal peduncle, and also described the technique for preparation of transverse sections of the first or marginal ray of the pectoral fin. This method, brought to our knowledge by Roussow (1947) who had already used it in a study of the Danube sturgeon (Roussow 1938), has the advantage of considerably simplifying both collection of material in the field and technical operations at the laboratory. The methods of obtaining material in the field differ according to whether the fish are to be tagged and released or killed for market. In the first case, a portion of one marginal fin ray is removed with pincers; in the second case, the anterior rays are cut off near the fin base with a knife. To obtain the transverse sections, the dry sample of a pectoral fin is placed in a 'Vise and the first ray sectioned near the basal region with the aid of a fine saw blade, such as used by jewellers. The slices, approximately 0.3 to 0.5 mm. in thickness, are placed in glycerine on a thin slide of glass and examined under the binocular microscope at low magnification. Figure 3 illustrates a magnified view of a section of bony ray of the pectoral fin as seen under microscope with transmitted light. Nine narrow and distinct zones can be counted from the centre to the lower edge, corresponding to the slow growth or to a stop in growth during successive winter seasons. The pictures, however, are not always as clear as this; for example, in individuals of slow growth, the winter marks are very close together and difficult to distinguish. Certain samples have had to be set aside because of abnormal development of the ray or because of an injury to the fin. The growth study of the sturgeon caught in Lake St. Francis is based on the examination of 329 specimens (13 of the 342 specimens were eliminated). The age is indicated in arabic numerals which represent the number of narrow zones observed on the section; thus the number 9, for example, indicates that nine narrow zones were observed on the section of the marginal ray and that this sturgeon has passed nine winter periods and has completed nine years. In this case, we say that this individual, caught during the course of its tenth year, is nine years old.

(1) We owe to Mr. Ivan J. Donaldson (Resident Biologist, Corps of Engineers, Oregon) the reference to the work of Chugunov, and a translation of Chugunov's paper which was submitted to one of us (correspondence, March 1948 T. P. C. ) 23

The average length and weight for each age indicated in Table 1 have been smoothed by the method of moving average of three to draw the curves given in Figure 4; in this figure, the curves for increase in length and in weight of sturgeon from Lake St. Francis are compared with corresponding curves taken from Harkness' study

Figure 3 Cross section (X 15, approximately) of the marginal ray of a pectoral fin of lake sturgeon. Sample from a specimen caught in Lake St Francis on July 9, 1947. Fork length, 28-5 inches; weight, 6 pounds; Sax, female immature; age, 9 years. Table I Mean lengths in inches and mean weights in pounds, according to age; sturgeon caught in Lake St. Francis during the summer of 1947.

Age Mean length Mean weight Number of completed years in inches in pounds individuals

3- ...... 16•5 1-0 4 ...... 20•1 2-1 5 ...... ^ 22-4 2•7 6 ...... 23-8 3-5 7 ...... 24-7 3-8 8 ...... 26•4 4•5 9- ...... -- 27-4 5-4 10 ...... 29•2 6-3 11 ...... 30•1 7•1 12 ...... 31-0 7•6 13 ...... 32-8 9•4 14 ...... 34•4 11-6 15 ...... 35-0 12-5 16 ...... 34-8 11-2 17 ...... 37-6 15-7 18 ...... 38•0 13-7 19 ...... 42-0 20-0 20 ...... 40-0 18-9 21 ...... 40-0 17•3 22 ...... 37•5 14-5 23 ...... 49-3 37-7 24

5 10 15 20 25 30 AGE-NUMBER OF YEARS

Figure 4

Curves of growth in length and in weight of lake sturgeon from Lake St. Francis (1947 material) and from Lake Nipigon (Harkness 1923). 25

(1923) of the sturgeon from Lake Nipigon, Ontario. According to this figure, based on the smoothed averages, it is noted that during the first years the growth in length of the sturgeon of Lake St. Francis is more rapid than the growth in weight, and that the opposite is true at more advanced ages. In fact, during the first five years the length increases at an average rate of 4.5 inches a year; between three and five years, the length increases two inches a year; between five and 10 years, the increase seems to maintain a rate of 1.4 inches a year, and thereafter, 1.2 inches a year. The weight during the first five years represents a mean annual increment of 0.5 pound; between three and five years this increment is 0.8 pound; between five and 10 years the mean i annual increment is 0.8 pound and between 10 and 15 years it is 1.2 pounds. Toward the twentieth year, the means are very irregular and the annual growth in weight seems to reach several pounds. In individuals of this size, it is, however, necessary to take into consideration the development of gonads; unfortunately our material in this group of individuals is too limited to enter into such considerations. Table II summarizes the rate of growth and the average increase in length and weight by periods of five years according to Figure 5, and similar data presented by Harkness (1923). It is evident, according to this Table and Figure 5, that the growth of sturgeon is much more rapid in Lake St. Francis than in Lake Nipigon, especially with reference to the weight. Table II Summary of the growth of sturgeon by five-year periods. The data of Lake St. Francis are compared with those of Lake Nipigon (Harkness 1923), where the total lengths have been converted to fork lengths.

GROWTH

Age I Length in inches I Weight in pounds completed years Lake St. Lake I Lake St. Lake Francis Nipigon Francis Nipigon

0- 5 ...... 0-20 0-17 0- 2 0- 1

5-10...... 20-29 17-24 2- 6 1- 3

10-15 ...... 29-35 24-29 6-12 3- 5

15-20 ...... 35-40 29-33 12-18 5- 8

20-25 ...... 40-45 33-37 18-36 8-12

Length-Weight Relationship The legislative restrictions of the governments concerned refer exclusively to the length of the sturgeon. On the markets, it is generally a question of the weight of the fish. It becomes important to show the relationship between the length and the weight of the fish. While taking into consideration that the majority of individuals were kept alive in tanks for several days, data on length and weight for both sexes were compiled for each length group by intervals of one inch. Table III shows that sturgeon of 28 inches in length weigh 5.6 pounds; those of 36 inches about 12.75 pounds and those of 42 I inches 22.3 pounds. These three lengths corresporid, respectively, to the minimum 26

lengths considered as legal for the Quebec section of the St. Lawrence; for the Quebec section of the Ottawa River and the Ontario section of Lake St. Francis; and for other Ontario waters. Table III Relation between length and weight, and value of coefficient of condition, K(FL), of sturgeon caught in Lake St. Francis during the summer of 1947-

Number of Mean length Mean weight Value of Individuals in inches in pounds K(FL)

2 ...... 16-1 0-9 2-16 3 ...... 17•1 1-1 2-20 1 ...... 18-0 1-5 2-57 3 ...... 19•1 1-8 2-58 ...... 7 ...... 21-5 2-5 2-52 15 ...... 22-2 2-8 2-56 17 ...... 23-1 3-5 2-84 24 ...... 24-1 4-1 2-93 20 ...... 25-0 4-3 2-75 24 ...... 26-1 4-4 2-48 17 ...... 27-1 5-4 2-71 32 ...... 28•0 5-6 2-56 18...... I ...... 29-1 6-2 2-52 27 ...... 30-0 7-1 2-63 16 ...... 31-0 7-8 2•62 22 ...... 32-0 8-5 2-59 13 ...... 33-0 9-5 2-64 14 ...... 34-0 10-6 2-70 5- ...... 35-0 11-6 2-71 17 ...... 36-2 12-9 2-72 9 ...... 37-0 12-9 2-54 4 ...... 38-0 15-9 2-90 6 ...... 39-0 16•1 2-71 8 ...... 40•0 19-1 2-98 2 ...... 41-0 22-1 3-20 4 ...... 42-0 22-3 3-01 1 ...... 43-0 22-0 2-77 3 ...... 44-0 24-0 2-82 ...... 1 ...... 46-0 30-0 3-08 ...... 1...... 48-0 38-0 3-43 ...... 1 ...... 50-5 37-5 2 - 91

Total number of individuals ...... 337 Mean value of K(FL) ...... 2-67

In order to measure the relative weight and to establish comparisons between different populations and between individuals of different size we have calculated the coefficient of condition for fork lengths of 337 specimens from the mean length and the mean weight, for each interval of one inch. This value is calculated according to the equation: K (FL) = P x 101 L3 where K(FL) = coefficient of condition, calculated from fork length measurements, P = weight in pounds, L fork length in inches. 27

This equation gives to K(FL) values varying between 2.48 and 2.93 for the length groups having more than 10 individuals (Table III); the average value for these individuals, measuring between 22 and 36 inches, is 2.66; among individuals of smaller size, the values decrease, while they increase among fish of larger size. For the total, the value of K(FL) is equal to 2.67. The value of the coefficient of condition thus apparently increases with size. The relationship between length and weight of the sturgeon of Lake St. Francis indicates a condition inferior to that observed in the individuals of Lake St. Peter (material of 1945), where the mean value of the coefficient of condition is in the neigh- borhood of 3.15 for individuals measuring between 32 and 38 inches; for the total, this value, based on 587 specimens, is 3.10 (unpublished data). These data seem to indicate that Lake St. Peter is richer in food than Lake St. Francis and that the sturgeon which live there are in general much fatter than those in Lake St. Francis. If the value of the coefficient of condition is calculated for individuals of the' same age according to their average lengths and weights (Table IV), an average of 2.60 (2.40-2.92) is obtained for individuals from 5 to 17 years of age; the value of K(FL) tends to increase with age. Table IV Value of coefficient of condition, K(FL), according to mean length and weight of each age; Lake St. Francis, 1947.

Age Number of Mean length Mean weight Value of completed years Individuals in inches in pounds K(FL)

5 ...... 22-4 2-7 2-40 6 ...... 23-8 3-5 2•59 7 ...... 24-7 3-8 2-52 8 ...... 26-4 4-5 2-45 9 ...... 27•4 5-4 2-62 10- ...... 29-2 6-3 2-53 11 ...... 30-1 7•1 2-61 12_ ...... 31-0 7-6 2-56 13 ...... 32-8 9-4 2-66 14 ...... 34-4 11-6 2-85 15 ...... 35-0 12-5 2-92 16 ...... 34-8 11-2 2-66 17 ...... 37-6 15-7 2-95

Total number of individuals ...... 298 Mean value of K(FL) ...... ' ...... 2-60

Sex and Maturity The sex was determined for 134 of the 138 individuals killed; 66 males and 68 females were counted. Examination of the degree of development and the state of maturity of the gonads revealed that three specimens only-two males and one female-had mature glands; these three specimens were caught at the end of Septen}ber. The two males had swollen, white testes, but the deferent canals did not contain milt; in the female, the eggs were 28

dark green and showed a black ring around the cicatricule. It is presumed that these fish would have spawned in the spring of 1948. The data on weight, length, and age for these specimens appear in Table V. The males were aged 15 and 21 respectively, and the female 23 years. Table V

Principal data on mature sturgeons caught in Lake St. Francis in late September, 1947.

Number of Length Weight Age, number Sex Collection in inches in pounds of years

F -310 ...... 40 18-75 15 Male

F-312 ...... 43 22 21 Male

F - 313 ...... 50•5 42 23 Female

Summary

As part of a survey of sturgeon fisheries in the St. Lawrence River and as part of a study of the biology of lake sturgeon, investigations were carried out in 1947, and the material collected at that time is briefly discussed in this pap&.

From June 21 to October 28, 1947, 342 lake sturgeon were examined; 138 were killed and 204 were tagged and released. The specimens ranged in size from 16 to 50 inches, fork length, and in weight from 0.75 to 42 pounds. The average length was between 27 and 28 inches and the weight between four and five pounds. Most of the sturgeon were caught by gill nets with three and one-half inch square mesh. Decline in the catch as shown by annual statistics, and the regulations, are briefly discussed.

The age was determined by sections of marginal rays of the pectoral fins. Indi- viduals of eight years constituted the dominant year class. The growth of sturgeon caught in Lake St. Francis is more rapid than the growth observed by Harkness (1923) in Lake Nipigon. The coefficient of condition, calculated on fork length measurements, gave an average K(FL) value of 2.67. Among the 138 specimens killed, the sex of 134 was determined: 66 males and 68 females. Only three mature fish were caught: two males 15 and 21 years old respectively and a female 23 years old.

Acknowledgments

The authors wish to express their gratitude to the Minister of Trade and Com- merce of Quebec, the Honourable Jean-Paul Beaulieu, and his Deputy Minister, Mr. Louis Coderre, for financial aid provided in carrying out this work and-for permission to publish. They also thank Dr. Georges Préfontaine, who supervised the general organization of the work, and Mr. J. M. MacLennan, Canadian Wildlife Service, for his great assistance in translating , the French manuscript. The graphs have been kindly prepared by Mrs. G. A. Bernier-Boulanger. Finally thanks are due to the fishermen of Lake St. Francis for their collaboration. 29 Literature Cited

CHUGUNOV, N. 1925. On the methods of Age Determination in Sturgeons. (From Asov Scientific Industrial Expedition). Bull. of Fisheries Economy, No. 11, pp. 33. CUERRIER, J.-P. 1945a. Rapports présentés à l'Office de Recherches Scientifiques sur Les inventaires biologiques et ichthyologiques de la régi on de Montréal et du Lac Saint-Pierre, Manuscrit. Mai 1945. CUERRIER, J.-P. 1945b. Les stades de maturité chez l'esturgeon du Lac Saint-Pierre. Bibi. de l'Off. prov. de Biol., Min. de la Chasse et des Pêcheries, Québec, MS 2212. Manuscrit. CUERRIER, J.-P. 1946. Plan for a survey of the Sturgeon (Acipenser fulvescens Raf.) in the Upper St. Lawrence River. Canadian Committee on Fish Culture, Ottawa; pp. 1-12; January 1946. Mimeo- graphed. GREELEY, J. G. 1936. Fishes of the Area with annotated List. A Biological Survey of the Lower Hudson Watershed. Suppl. 26th Ann. Rept. N.Y. State Cons. Dept.; pp. 43-103. HARKNESS, W. J. K. 1923. The rate of Growth and the Food of the Lake Sturgeon (Acipenser rubicundus LeSueur). Univ. Toronto Studies, Biol. Ser., No. 18, pp. 13-42. ROUSSOW, G. 1938. Contribution à l'étude de l'extérieur et de la croissance de l'Acipenser ruthenus L. Annales de l'Institut Nat. Zootech. de Roumanie. T. VI, pp. 1-17. ROUSSOW. G. 1947. Application de la méthode des coupes transversales du premier rayon de la nageoire pectorale et la détermination de l'âge chez l'esturgeon de lac (Acipenser fulvescens Raf.). Soc. Biol. de Montréal. Comptes rendus. Revue Canad. de Biol., dol. 6, No. 2, p. 362. (Titre seulement). 30

,,Red Sore" Disease of Pike in Mont Tremblant Park District, Quebec by

Leo Margolis Graduate Assistant, Institute of Parasitology, McGill University, Macdonald College, Que.

Reed and Toner (1941) investigated a septicaemic disease of pike (Esox lucius) known as "red sore". The disease, they reported, was prevalent in the natural waters of Eastern.Ontario but had never been reported elsewhere. They believed that it did .not occur in the Province of Quebec. However, it is now reported for the first time in this province. The etiological agent of "red sore" of pike is a bacterium, Pseudomonas hydrophila (Chester), which is also responsible for the condition in frogs, known as "red leg" (Emerson and Norris 1905, Sanarelli 1891). Reed and Toner (1942) have suggested that frogs act as carriers of the organism from one body of water to another. The disease in pike takes the form of a haemorrhagic septicaemia, with external lesions consisting of red areas, from which the disease gets its name. The lesions vary from slight petechial haemorrhages in the skin to deep red areas several centimetres in diameter. In late stages of the disease, the lesions appear as red necrotic areas, involving the muscle tissue. The internal organs, on gross examination, appear normal, except for the kidney which is often darker and softer in texture. Reed and Toner (1941) regularly isolated Ps. hydrophila from the lesions and from one or more internal organs, i.e. heart blood, kidney, spleen or liver. The route of infection was not determined. While collecting several species of freshwater fish from lakes in the Mont Tremb- lant Park, in the summer of 1949, to study the bacterial flora of the slime and intestines, a number of pike were taken from Lake Monroe and Stair Lake which showed the characteristic lesions of "red sore". Three of these fish were examined bacteriologically. Ps. hydrophila was always isolated from the lesions and heart blood. Frogs, inoculated subcutaneously with broth cultures of the organism in doses of 1-10 cc or 1-100 cc; died within two to four days. Upon autopsy, the frogs showed the characteristic syndrome of "red leg" and the test organism was isolated from the heart blood and peritoneal fluid. Frogs inoculated with sterile broth showed no signs of illness one month after the injection. Lake Monroe and Stair Lake are connected by the Devil River. Althoug': a survey was not carried out to determine the distribution of Ps. hydrophila infections of fish in Quebec waters, it is apparent that the disease occurs in the Devil River water system and any lake or river receiving water from the Devil River is a potential source of infection.

Financial assistance for the research was given by the National Research Council of Canada. 31

It is interesting to note that Ps. hydrophila was isolated from the intestines of two pike and the slime of another, with none of these fish showing any signs of illness. These fish may have been in an early stage of infection with no visible symptoms.

Literature Cited

EMERSON, H. and NORRIS, C. 1905. "Red leg"-An infectious discase of frogs. J. Exp. Med., 7: 32-58. REED, G. B. and TONER, G. C. 1941. Red sore disease of pike. Can. J. Res. D, 19: 139-143. REED, G. B. and TONER, G. C. 1942. Proteus hydrophilus infections of pike, trout and frogs. Can. J. Res. D, 20: 161•166.

SANARELLI, G. 1891. Ueber einen neuen Miktroorganismus des Wassers, wekher fûr Thiere mit verdnderlicher und konstanter `ïemperatur pathogen ist. Centr. BaI{t. Parasitenl{., 9: 193-199 and 222-228 32

On the Theory of Adding Nutrients to Lakes with the Object of Increasing Trout Production by

F. R. Hayes Zoological Laboratory, Dalhousie University, Halifax, N.S.

The object of tampering with the economy of a lake is to increase the fish crop. There are few experiments on record showing clearly what added nutrients will do in this direction. There are however, records for a large series of lakes, principally European, 'where inadvertent fertilization has occurred as a result of domestic sewage or agricultural drainage (Hasler 1947)- A noteworthy example is Lake Zurich, Switzerland, a lake composed of two basins separated by a narrow passage. Less than 100 years ago both basins were clear and supported a commercial crop of trout and whitefish. For the last 50 years or more, one basin has received urban drainage from communities numbering 110,000 people. One result has been the development of algal scums, which made the lake unattractive. Moreover decomposition of the added organic matter produced a deficiency of oxygen in the deeper water so that trout and one species of whitefish disappeared altogether; two others are rarely seen any more. Other species, largely coarse fish, have replaced them. The other basin, which receives no urban drainage, has changed little. Hasler assembled records for 37 lakes which had been unintentionally enriched, and whose history followed within a few decades, that of Lake Zurich. In all cases the results were not in the best interest of ideal lake use by man. Continuous nutrient drainage into a lake will undoubtedly produce enrichment, but if coarse fish are present they are likely to be favoured at the expense of trout, and there will probably be other unwanted results. Intentional Enrichment of Lakes Turning now from unintentional to intentional enrichment, two important differences should be noted. First, the amounts of nutrient added will be very much reduced, for obvious economic reasons. Second, the addition will not be continuous, but will occur when fertilizer is spread over the lake once or twice a year. The question for us then, is whether one addition or an occasional addition of fertilizer can improve trout production. It may be said at once that there is no experiment known to the writer, in which permanent improvement in trout fishing has been demonstrated, following such fertilization. The nutrients which come to mind are those known to be useful in agriculture, namely nitrogen, potassium and phosphorus. When these substances are added they always disappear rapidly from the water, so that some 90 per cent is gone within a month or less. This has often been taken as evideqce of rapid utilization by the animals and plants in the lake, and it has been thought to prove that the added material was acting as a nutrient. 33

Through the recent availability of radioactive phosphorus we have been able to check this idea, by adding minute quantities of the tracer to lakes (Hayes et al, 1951). In our experiments there was no appreciable initial increase in the phosphorus present, nor did any later decline occur. We were simply following the behaviour of a few marked atoms. Nevertheless, the same decline in the marked atoms occurred, that others have seen when tons of nutrient were added. In our experiment the proposition that some enhancement of growth took place is untenable. We were therefore led to doubt the validity of the general interpretation. Instead of "disappearance" from the water, we concluded that there was a continuous exchange of phosphorus going on between the water and solids in the lake. ("Solids" is taken to include the plants and animals in the lake as well as a thin layer of participating mud, perhaps 1 mm. thick). Under ordinary conditions, one atom of phosphorus comes out of the solids for every one that enters from the water. If we upset the balance by placing a number of marked atoms (or a ton of fertilizer) in the water, the added atoms will tend to leave the water, so many per cent per day. At the same time there is a return of material from the solids, so much per cent per day. How- ever, in the first stages after addition of material, little can return from the solids because little has yet entered them. As time goes on, and there is more and more material in the solids, the return from them becomes appreciable and tends to hold up the phosphorus (or radiophosphorus) content of the water. We set up an equation to describe the exchange, which it is not necessary to develop here. The essence of the matter is that a lake is not, as one might think, a body of water containing nutrients, but an equilibrated system of water and solids, and that under ordinary conditions, nearly all the nutrients are in the solid phase. What seems to be a great deal of nutrient material (in terms of water) is really only a small fraction of the whole system. When added to the lake, it will partition itself between water and solids, so that neither phase will be much richer than before.

Money Transfer Illustration An understanding of how exchange of ions might be confused with their apparent removal, may be illustrated by consideration of money transfers. Suppose that most of the money in a town at any given moment is in the banks. Suppose further that one dispersed a supply of marked bank notes at random through the town. Within a few days, it would be found that under normal processes of commerce most of the marked notes had moved into the banks. This would not mean that the banks were specifically removing marked notes frôm circulation nor that the ratio of money in the bank to money outside had changed. It would merely be proof that the banks were engaged in active trading, which is the important consideration in the present case. Incidentally, if we could remove all the money from the town generally (outside the banks) there would be an outflow from the banks to restore the equilibrium again. That kind of experiment in limnology is not as easy as the other one (adding something to water), but we have done it in the laboratory using radiophosphorus. Results were as expected. It is implicit in the exchange system that an equivalent of something else is liberated for every atom of phosphorus that goes into the solids. We are not yet sure what the exchanging substances are, but they may `be humic acid radicles. 34

Two questions suggest themselves. First, what about other nutrients, and do they behave like phosphorus? Second, what about the long term picture, and do the banks ever disgorge their holdings for the general benefit? Of the first question we can say that when nitrogen or potassium are added to lakes they disappear from the water in the same rapid way as phosphorus (Hayes, 1947 for nitrogen). A direct demonstration of the exchange mechanism is lacking, except for some inconclusive laboratory experiments of Breest (1925) on potassium. A general finding is that phosphorus is the key nutrient material. Thus in carp ponds, phosphorus by itself is about as valuable as a mixture of all three nutrients (see Neess, 1946). Nitrogen can probably be synthesized from the atmosphere for the use of aquatic plants, as happens in the root nodules of land plants. The second question about long term effects, requires some chemical consideration. It may be stated first that there is no clear demonstration by anybody, that nutrients added one year have reappeared the following season to enhance the water. There does occur normally in lakes, an increase in nutrient material in the water when the ice breaks up and the lake is stirred (Pearsall, 1930). The exact quantity of, say phosphorus, is rather variable in the spring, and might be incorrectly credited to additions during the previous summer. The chemistry of phosphorus in lakes is better known than that of other nutrients, having been worked out by Einsele (1938) in conjunction with iron chemistry. There is often an excess of iron available which, in the presence of oxygen, precipitates practically all of the phosphorus out of the water as ferric phosphate, FePO4. The remainder of the iron is precipitated as ferric hydroxide. In Nova Scotian trout lakes, there is not generally sufficient removal of oxygen from the depths in summer to permit any summer reversal of these precipitation reactions. If phosphorus is added in summer to a lake whose depths still have oxygen, the few per cent of phosphorus which remain in the water after equilibration with solids (as above described) would presumably stay there until either washed out through the outlet stream, or precipitated by iron coming into the lake. During this interval the extra phosphorus would be available for stimVlation of plant growth, and indeed bursts of surface algae are often observed, e.g. in New Brunswick by Smith (1945), and in Michigan by Ball (1948). A temporary increase in trout growth and survival was also observed. Considerations of colloid chemistry developed by Ohle (1937) and Einsele suggest that the residuum of phosphorus referred to in the last paragraph, may disappear from solution and still remain available for nutritional purposes. It becomes adsorbed on an iron hydroxide gel in the mud and stands, so to speak, as a savings account to be drawn on as necessary by the plants in the water. If an iron hydroxide gel is present, as in some lakes but not all. the phosphorus will partition itself between dissolved and adsorbed phases in accordance with the law describing adsorption of gases on surface- active solids such as carbon, i.e. y=kx" where (in our case) y is the phosphorus in the water, x the phosphorus attached to the iron hydroxide gel, and k and n are constants. Diminution of y (by its removal to form aquatic plants, etc.) will cause more to be given off from the gel. Similarly a man spending money, keeps a fixed amount in his pocket by drawing as necessary on his bank 35 account. The account wi111 eventually become exhausted unless a deposit is made. Counting a man's pocket money in such circumstances, does not tell much about his economic solidity.

Oxygen May Be Depleted in Some Lakes There are some trout lakes (although apparently not many in Nova Scotia), which are rich enough to have their depths depleted of oxygen during the summer. By richness is meant here, reducing power of the mud, a phenomenon which seems to parallel the results of elaborate botanical surveys of plant types and abundance, etc., etc., in various lakes (Mortimer, 1941 and 1942). If the water above the mud does have its oxygen reduced to about one per cent of its saturation value, say 0.1 mg. per litre, a new equilibrium sets in, initiated by the reduction of ferric iron to ferrous iron. Thus ferric phosphate, which is very insoluble, becomes ferrous phosphate, whose ions are quite soluble and pass into the water above the mud and so are moved gradually throughout the lake. In this reaction there would be liberated, about 0.55 gm. of phosphorus for each gm. of iron. How- ever, extra iron often gets into the water through the decomposition of ferric hydroxide with the production of soluble ferrous ions. Thus in the Punchbowl, a small lake near Halifax, there was in the water above the mud in midsummer, 700 parts per billion of iron and only 30-40 p.p.b. of phosphorus. The liberated iron and phosphorus will circulate in the deeper parts of the lake and some of it eventually reaches the boundary zone, a few feet below the surface, in which oxygen is found. Here the precipitation reaction again sets in and ferric phosphate is formed, together with ferric hydroxide (the latter reaction using up any excess iron that is present). The water at the boundary zone is often rust coloured by reason of the hydroxide. If the lake is approximately neutral or slightly acid, none of the iron or phosphorus is likely to reach the surface, where oxygen is plentiful. Most of the trout lakes we have studied in Nova Scotia are however, quite acid, the pH being 5.5 or less. In such waters, oxidation of ferrous iron through the medium of dissolved oxygen proceeds very slowly and may take weeks. In fact it may not be a practical occurrence by inorganic means at all, but be the result of iron-oxidizing organisms in the lake as is the situation in agricultural soils (Gleen, 1950). Hence ferrous iron will be carried throughout the whole lake, and also phosphorus, without precipitation. In this way phosphorus may become available to plants in the shallow waters. Similarly, if ferrous iron and phosphorus entered from streams, they might remain together in the lake water for some time. We have not happened to encounter a good trout lake in Nova Scotia fulfilling both the above conditions, namely extreme summer oxygen depletion in the depths and marked acidity. Doubtless, however, they exist. The absence of trout in the Punch- bowl for instance (which does have these characteristics) is more likely due to lack of spawning beds in the area than to its chemical make-up. Consider now a lake-type with marked summer oxygen depletion at the mud surface, and with neutral or alkaline reaction. As above noted there will be immediate oxidation of any ferrous iron which approaches the surface, with consequent precipitation of phosphorus. However, an additional reaction may enter provided sulphur is present in the mud as hydrogen sulphide. The smell of H2S is often noticed in lake 36

muds. Suppose a certain amount of ferrous iron and a certain amount of hydrogen sulphide occur together above the mud. Whether under such conditions the substances unite to form insoluble ferrous sulphide, depends decisively on the pH. The higher the pH is, the greater will be the tendency to form FeS. If several mg. per litre of H2S are present in the water, and the pH is 7.2, only about 0.1 mg. per litre of FeS can exist in solution-the remainder will be precipitated. At higher pH values the amount that can remain in solution is still further reduced. It follows that if sulphur is present at alkaline pH's, practically no iron can escape from the mud and any phosphorus which gets into the water is free to stay there and contribute to the nutritive cycle. Nutrients are usually added to lakes in solid form and a fraction often sinks to the bottom undissolved. Such a fraction presumably enters into the equilibration system in some way, but we are not in a position to allow for it quantitatively at the present time. Presumably an extra term in the equation would be required. It may be that this solid material resting on the bottom acts somewhat as fertilizer does when added to agricultural land, and produces a direct stimulus to productivity in the mud, probably including bacteria. In Crecy Lake, M. W. Smith found that an increase in the bottom fauna was maintained during three seasons following fertilization, but diminished in the fourth. The second winter after fertilization, there occurred in one lake, a marked oxygen depletion under the ice. In another lake similarly treated there was no depletion (private communication). Ball (1948) also observed winter oxygen depletion, delayed one year, after treatment with fertilizer. It would evidently be desirable in future work, to distinguish between solid fertilizer added to the bottom, and dissolved fertilizer added to the water.

Conclusions If nutrient salts are added to a lake by way of fertilization we may expect some 90 per cent of them to disappear from the water in an exchange reaction within a few weeks. The remaining 10 per cent is likely, through one or more of the mechanisms that have been outlined, to remain in the water (or available.to the water) and so contribute to the initiation of algal growth, leading to animal plankton growth and thence to fish growth. None of the extra material is likely to be seen during a second summer. While information is less complete as regards the survival of potassium and nitrogen, than concerning phosphorus, our present view is that about the same per cent of each would survive in the water after equilibration had taken place. As a conservation measure, the general fertilization of lakes-does not appear to be an economic procedure. For a privately controlled lake, as a hobby for a wealthy individual or fishing club, it constitutes an interesting experiment. If the lake has no coarse fish to replace trout under conditions of high fertility, large yields of trout might be expected from intensive fertilization. This seems to be the situation in Prince Edward Island, where the ponds receive extensive drainage from good agricultural land. Alternatively the coarse fish might be selectively poisoned off in conjunction with a programme of fertilization. We have found selective poisoning, by removal of coarse fish from the shallows while leaving trout in the depths, to be extremely promising. Finally it should be mentioned that a lake supports its various crops as a sort of pyramid-shaped set of blocks. At the base there is a large supply of nutrient material. 37

The next smaller block above comprises the plants, on which feed a still smaller quantity of small invertebrate animals. On these feed the fish, a small standing crop at the top. The system is in a state of balance and can only permanently support so many fish. If a large number of extra fish are added they will simply die off or stay in a half- starved condition until the top block is, so to speak, cut to its proper size in the pyramid. This perhaps explains why it is observed that when trout are planted in a barren lake, they often do well for a time and then the new population suddenly collapses. Thus Rawson (1947) reports that in six Rocky Mountain lakes where trout were planted, there was rapid growth, followed by sudden deterioration and gradual recovery. "It is believed" he says, "that the difficulty results from over population with large fish and their consequent failure to find suitable food. Since these fish are of nearly uniform size the population is unable to adjust itself by cannibalism." The same type of collapse appears to have occurred following stocking of two barren Nova Scotian lakes which have been under fairly close control by private individuals. It may be that trout survive where they do, because they can tolerate somewhat more adverse conditions, nutritionally speaking, than competing fish. If conditions are made more generally favourable, the competing coarse fish or birds would thrive at the expense of the trout. There would also tend to be a reduction of the oxygen supply, to which trout are especially sensitive. Trout can be maintained in great abundance where food is provided and competitors kept away, for instance in hatchery ponds. Similarly one might think of the penguin, a helpless bird which would be at the mercy of predators, except that it lives in surroundings that kill off its potential enemies. Now if we could imagine making life easier for the penguins, say by warm- ing up the Antarctic, they might well be eliminated by newly arrived competitors. Grateful acknowledgment is made to the National Research Council, the Nova Scotia Research Foundation and the Nova Scotia Department of Trade and Industry for support of our lake studies. Literature Cited

BALL, R. C. 1948. Fertilization of natural lakes in Michigan. Trans. Amer. Fish. Soc. 78. 145. BREEST, F. 1925. Uber die Beziehung zwischen Teichwasser, `I'eichschlamm und `reichunurgrund. Arch. Hydrobiol. 15. 422. EINSELE, W. 1938. Uber chemische und kolloidchemische Vorgange in Eisen-Phosphat-Systemen unter limnochemischen und limnogeologischen Gesichtspunllten. Arch. Hydrobiol. 33. 361. GLEEN, H. 1950. Biological oxidation of iron in soil. Nature. 166. 871. HASLER, A. D. 1947. Eutrophication of takes by domestic drainage. Ecology. 28. 383. HAYES, F. R. 1947. Report on Inland Fisheiies. Ann. Rept. Dept. of Trade and Industry, Nova Scotia. p. 82. HAYES, F. R., McCARTER, J. A., CAMERON, M. L. and LIVINGSTONE, D. A. 1951. On the kinetics of phosphorus exchange in lakes. In press. MORTIMER, C. H. 1941 and 1942. The exchange of dissolved substances between mud and water in takes. J. Ecol. 29. 280 and 30. 147. NEESS, J. C. 1946. Development and status of pond fertilization in central Europe. Trans. Amer. Fish. Soc. 76. 335. OHLE, W. 1937. Kolloidgele als Tjahrstoffregulatoren der Gewdsser. Die Naturwissenschaften. 25. 471. PEARSALL, W. H. 1930. Phytoplanltton in the English Lakes. I. The proportions in the waters of some dissolved substances of biological importance. J. Ecol. 18. 306. RAWSON, D. S. 1947. Deterioration of recently established trout populations in lalles of the Canadian Roclties. Canadian Fish Culturist. 2. 14. SM1TH, M. W. 1945. Preliminary observations upon the fertilization of Crecy Lake, New Brunswick. 6 Trans. Amer. Fish. Soc. 75. 165. 38

Experimental Rearing of Yellow Pikeperch Fry in Natural Waters by

W. B. Scott, D. N. Omand and G. H. Lawler

In an effort to seek more efficient ways to utilize the output of hatcheries in Ontario, attention has recently turned to the possibility of using natural waters as rearing ponds. Such an attempt was recorded by Speaker (1938) who indicated that yellow pikeperch could be reared to fingerling size in comparatively large numbers under favourable conditions. It was hoped that placing newly hatched fry from hatcheries in highly productive waters from which competitors and predators had been removed, would result in high survival, making it possible to plant fingerling fish, without the expense attendant upon retaining the fry in hatcheries. At the instigation and with the enthusiastic assistance of 'C. F. Kolbe of the W. F. Kolbe Fish Company, Port Dover, Ontario, such an experiment was attempted in Silver Lake at Port Dover during the summer of 1949. Silver Lake is a shallow body of water about 1,200 yards in length and averaging about 150 yards in width, formed by a dam across the Lynn River, in Woodhouse Township of Norfolk County (Figure 1). The upper end is marshy and shallow, averaging about two feet in depth. The lower end averages about eight feet in depth with a few holes of up to 12 feet in depth. There is a continual flow of water through the lake all summer from the Lynn River. The water is warm and rich in organic and inorganic suspension. The bottom is principally very deep clay mud. The area of open water is estimated to be about 55 acres. It was believed that this environment would be satisfactory for the production of yellow pikeperch (Stizostedion vitreum vitreum) and this species was chosen for the experiment. Reclamation Previous investigation had shown that Silver Lake cQntained a large population of carp (Cyprinus carpio), common suckers (Catostomus commerconnii), goldfish, bull heads (Ameiurus nebulosus), sunfish (Lepomis gibbosus) and minnows of various species. It was necessary to reduce this population as much as possible before beginning the experiment. In order to reduce the amount of water to be dealt with the water level was lowered by removing stop logs from the dam on Apri124, 1949. By the time the app'ication of poison was begun on April 26 the total area of open water was reduced to an estimated 30 acres averaging two feet in depth. Large areas of mud flat were exposed. A strong stream flow continued to enter the upper end of the lake bed, flowing through a fairly restricted channel in the upper half of the lake,"into the large shallow pool which remained at the lower end. At 10 a.m. on April 26 poisoning was begun. Forty pounds of Fish-Tox' was added to the water by dragging half-full burlap sacks through the water. It was

A commercial preparation specially prepared for fish aadication. 39

doubted at the time whether a toxic concentration was obtainable throughout the lake due to the large volume of water entering the upper end, and due to the in- accessibility of some pools isolated by mud banks which could not be crossed on foot. By 4 p.m. a considerable number of fish were dead, this first kill consisting principally of blunt nosed minnows (Hyborhynchus notatus), perch (Perca fiavescens) and sunfish.

LAKE E R I E

?V2 I MILE I I

Figure 1.

Map of Silver Lake, Port Dover, Ontario.

In order to increase the concentration, 200 pounds of derris dust was obtained, consisting of 15 per cent cube root containing 5 per cent rotenone and 85 per cent inactive ingredients. This second application was begun at 8 p.m. at the upper end of the lake, the dust being mixed with water in a tub and the emulsion poured into the stream continuously for two hours. I 40

The entire addition of poison amounted to 40 pounds of Fish-Tox containing 5 per cent rotenone and 30 pounds of cube root containing the same percentage, or 70 pounds of compound containing 5 per cent rotenone. It was difficult to estimate the concentration attained in the water owing to the flow entering the upper end, but it is believed that a concentration of approximately 0.5 ppm. by weight of 5 per cent rotenone was achieved. Examination at 7 a.m. April 27 revealed large numbers of dead fish floating in bays and backwaters. These were principally carp, suckers and goldfish. No attempt was made to estimate the exact number of fish killed but 42 individuals of

Figure 2. Fish killed in Silver Lake, Port Dover, O. by treatment with 0.5 ppm. of 5% rotenone 27 April, 1949. These are mainly carp and suckers. various species were counted opposite one ten-foot section of shoreline. Such a concentration was observed over at least one-quarter mile of shore at the lower end of the lake (Figure 2). Certain species present in the first kill were not noted in the second. Among these were perch (Perca flavescens) and large mouth black bass (Micropterus salmoides). Of 42

the latter only one was observed. It is believed that these fish were either washed out alive when the lake was drained, or sank into the bottom when killed and did not appear on the shore line. The dam was replaced on May 2 and the lake allowed to fill. A considerable disposal problem was created by the large numbers of dead fish.

Planting On May 23, 1949, two million newly hatched yellow pikeperch fry were planted in the upper half of Silver Lake. Lake temperature on the surfacé at the time was 640F. The fry were brought from Collingwood hatchery and were tempered carefully before planting in the lake. This was repeated on May 25 and May 27, total plantings amounting to six million fry. Observations made as the fish were being planted, however, indicated that a much smaller number were actually alive at planting, loss in transit amounting to an estimated 40 per cent.

Growth of Planted Fry Various types of gear were devised to attempt to sample this population. During the initial stage the most successful was a large cone shaped trawl of wire screen, six feet in diameter at the open end. In Table 1 numbers and sizes of successive samples are shown. After August 11 it was apparent that the samples could no longer be averaged due to the appearance of two distinct size groups but it was obvious that growth continued after this date. Individuals up to ten inches in length were taken during the removal operations in October. This rate of growth compares favourably with that observed in Lake Erie by Adamstone (1922). His observations indicated a length of 11.0 cms. (presumably total length) at the completion of one year of growth. Cleary (1949) shows that the same species from Clear Lake, Iowa, reached a length of 14.1 cms. at the end of the first year. Table 1. Average total length of samples of yellow pikeperch taken during 1949.

Date Average total length No. in sampler 27 May ...... , .... 8 mm. 10 26 June ...... 42 mm. 2 29 June ...... 53 mm. 3 4 July...... 61 mm. 4 11 July ...... 74 mm. 9 IS July ...... 81 mm. 11 25 July ...... 85 mm. 10 8 Aug ...... 94 mm. 9 11 Aug ...... 98 mm. 12

Physio-chemical Conditions Investigation of water conditions in •Silver Lake on August 3 revealed that temperatures ranged from 75°F at the inflow to 82°F. at the outflow. Little variation was found from top to bottom throughout the lake. pH ranged from 7.4 on the bottom to 8.6 on the surface. Dissolved oxygen, as determined by Miller's method, measured 4.2 cc/litre in the deeper waters, and up to 12 cc/litre on the surface. 42 Fingerling Removal and Transfer The question of the best method for removal of the fingerlings for transport to Lake Erie was under contemplation in August. A trap net was suggested and one of small mesh was provided by the Department of Lands and Forests. This was a six- foot net of the ordinarycommercial type, except for the crib which was of Z-inch mesh. This was set on August 5 at a point on the north side of the lake about halfway from either end. When lifted on the morning of August 6 this net contained about 400 yellow pikeperch fingerlings, together with several hundred young of the year of carp, goldfish, bullheads and sunfish. It was felt that this method of removal would be satisfactory, but owing to a shortage of personnel no further attempt to fish the lake was made until September 8. On that day two small meshed trap nets were set in Silver Lake, and one three-foot hoop net. A second hoop net was added on September 14. Fish taken were placed in a retainer net until all lifts for the day had been made, and then placed in cans for transport. They were planted in Lake Erie about one mile off the mouth of Port Dover harbour. In the course of this fishing many young carp, suckers, sunfish, etc., were taken in the nets. These were believed to be the progeny of the adult fish of these species which escaped poisoning in the spring. The fact that very few adults were taken indicates that although a complete kill was not obtained a very high percentage of the population was destroyed. The very high numbers of young taken indicate that spawning conditions were excellent after the population had been drastically reduced. High survival and rapid growth of fry were indicated. It is felt that this points to the necessity of obtaining a 100 per cent kill in any reclamation work, since if any spawning adults are left, the reduced competition and predation tend to make for very rapid repopulation of the water. A tendency for individuals to fall into two size groups, one considerably larger than the other, was first noticed during the test netting on August 5. By the time actual removal had begun this was considerably magnified, one group averaging about four inches in length, the other about 8.5 inches in length. The smaller size group contained a larger number of individuals. This bimodal tendency was attributed to cannibalism by the larger individuals, a supposition which was borne out by stomach analyses on a few of them. It was felt that this cannibalism had seriously reduced the total population by the time netting had begun. If the removal had been started early in August, before this divergence in size had reached serious proportions, the ultimate yield of individuals might have been substantially greater. Speaker (1938) reached a similar conclusion. Fish were removed from Silver Lake from September 9 to October 15, the total yield amounting to 6,200 fingerlings. Weather turned abruptly cooler about the middle of October and catches fell off sharply. It is believed that the limited fishing effort,which we were able to apply on the lake was a large factor in reducing the total yield, since only a small portion of the lake was being fished at any given time. In addition to this, many settings were exploratory. That is, it was necessary to set a net in an unfished area for one night to learn if a catchable population was present. If no catch was recorded, the net was moved and another area tried. If a large number of nets are available, a greater area of lake may be fished at any one time, and the information gained may be used in making further sets. 43

Conclusions It is believed that this experiment indicates the feasibility of retaining yellow pikeperch in a pond over one growing season for subsequent planting in other waters. Fry survival was fairly high, and it is reasonable to believe that the fingerlings which were planted in Lake Erie were better able to meet and overcome the factors of predation and competition than fry would have been. It is recognized, however, that from an economic point of view the results were doubtful. In addition to the labour involved in the manipulation of dams, and reclamation, a good deal of labour was expended in removing the fingerlings. Certain refinements of technique could reduce this considerably. If complete destruction of the previous population had been achieved the time-consuming work of sorting the fingerlings from the coarse fish in the nets would have been eliminated. A much more intensive fishing effort could have been applied had the proper nets been available. This would have removed the desirable fish in a shorter time, and reduced the cost of day labour. It is noteworthy that catches made in the bright, warm weather of early September were considerably higher than catches made in the cooler weather of late September and October. Application of the fishing effort in August would probably have yielded many more fish per unit of effort than application later in the year. It seems reasonable to believe that the period immediately after hatching must be crucial in the life cycle of any species. If this is so, then placing the fish in an environment which has been treated to reduce competition and predation should result in a high fry survival. It is considered that this experiment in Silver Lake supports the above belief, and if the technique were improved as indicated above, such a project could offer a more efficient way of using the products of our hatcheries, at least as far as this species is concerned. Literature Cited

SPEAKER, E. B. 1938. Pond rearing of wall eyed pike. Prog. Fish. Cult. No. 36, Feb.-Mar., pp. 1-6. CLEARY, R. E. 1948. Life history and management of the yellow pikeperch, Stizostedion vitreum vitreum, (Mitchell) of Clear Lake, Iowa. Iowa State Coll. Jour. of Sci., 1949, pp. 195-208. ADAMSTONE, F.B. 1922. Rates of growth of the blue and yellow pikeperch. University of Toronto Studies, Pub. Ont. Fish. Res. Lab., No. 5, pp. 77-86.

1 44

Further Observations upon the Movements of Speckled Trout in a Prince Edward Island Stream by M. W. Smith Senior Biologist, Atlantic Biological Station, Fisheries Research Board of Canada, St. Andrews, N.B.

The movements of speckled trout into and out of Ellerslie Brook, Prince Edward Island, have been under observation since June, 1946, in connection with a study of the relationship between the sea-run and brook populations and of the effects on these stocks of making artificial ponds. The movements of the trout during the first 15 months of observation (Smith, Fish. Res. Bd. Can., Prog. Rep. Atl., No. 43, Note No. 107, pp. 9-13, 1948) suggested a definite pattern, but subsequent observations have shown that the movenients vary from year to year. The trout moving into and out of Ellerslie Brook are captured in a two-way fish trap which is situated near the head of tide. The trap is operated throughout the year. Daily records are obtained of the number of trout that move each way. On its first passage each trout has a numbered monel metal tag attached to the lower jaw. During the angling season from April 15 to September 15 a creel census is taken of the trout angled from the brook and from the estuary below the trap. Ellerslie Brook, including one tributary, has a total permanent length of about four miles, but not more than one-half that length supports trout over one year in age during the summer months. The drainage area, consisting in large part of productive farming land, is about eight square miles. The brook is tributary to Smelt Creek, which in turn is an arm of Malpeque Bay.

The Movements As illustrated in Figure 1, the migrations of the trout may be roughly divided into two categories: (1) those that have recurred each year at about the same time, and (2) those that have been more sporadic but, in some instances, involving large numbers of trout. Of the first category are the movements up-stream in June and July, and up- and down-stream during the fall and early winter (October to December). The early- summer inward movements are quite well known to resident anglers because of their comparative regularity and their contribution to the angling in the streams at that season, and have been termed "strawberry runs". In 1948 this movement was in two pulses, while in 1949 it started earlier than usual, with the result that a good number of trout entered the brook in late May. Less appreciated by the general public are the upward movements of trout from salt water each year during the spawning period in the fall and early winter. During the same period there have occurred large outward movements from the brook. It is to be understood that the trout involved in the up- and down-stream fall runs are for the most part different individuals and not the same fish going through the traps several times during a short period of time. 45

6 1946 4 UP

DOWN

1947 UP Ll I I

WN 40

60 1948 40 UP

- --] Aj L "^

20 OWN 4

i I

6 I949 4 UP 2 I - -

DOWNT' 4 IT ' _ 6

JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. Figure 1.

Migration of trout into and out of Ellerslie Brook in numbers per day. 46

Of the second category of trout movements, which appear to occur in addition to. rather than in place of the more regular movements just discussed, the most noteworthy are those upward in April, 1947 and 1949, and the extensive downward run in May,. 1949. The relatively small downward runs in February, 1948, and March, 1949, are also of particular interest in demonstrating activity of trout while the brook is covered with ice and snow. But for these instances, however, few trout apparently move at that season. August and early September are also periods of little migrating activity. It is not intended in this report to inquire into the possible causes of the observed trout movements as the pertinent data have been incompletely analysed. Suffice it to report that a number of factors-height of water, change in water level, temperature of water, size and maturity of the trout-are involved. Relation to Anglers' Catches It is shown in Table I that the anglers' catch for 1949 was approximately 100 per cent greater than that in either 1947 or 1948, for which two years the angling record was quite constant with respect both to the number of trout captured and the rate at which they were taken. Tagged trout, that is trout which have moved through the fish trap, were responsible for much of the increased 1949 catch. Thus, the improved angling was correlated with the greater migratory activity of the trout in April, May and June, 1949, and also, so far as the records of the proportions tagged have been analysed, with a larger number of trout entering Ellerslie Brook from other areas. The possibility of a greater take of Ellerslie stocks is not, however, to, be overlooked. In the programme at Ellerslie Brook one of the more important criteria by which the effects of forming a pond upon the trout stock were to be gauged was the anglers' catch from year to year as revealed by the annual creel census. It was planned to study the movements of the trout from 1946 to 1950 before building a dam. By 1950 it was anticipated that a "normal" level for the catch without a pond would be established. Certainly the marked difference that was found between the catches of 1948 and 1949 was not expected, and has necessitated a continuance of the study without pond formation to ascertain whether the catch for 1949 was unduly high and that for 1947 and 1948 more "normal". The findings at Ellerslie Brook have illustrated clearly the difficulty of establishing a reasonably constant control level for comparative measurements of fish production in nature, in this case the yield of trout to anglers from a small. stream. Table I. Yield of trout to anglers, Ellerslie Brook.

1947 1948 1949

Tagged ...... 501 502 1,246

Untagged ...... 640 553 756

Totals ...... :...... 1,141 1,055 2,002

Number per rod-hour ...... 1.5 1.5 1.7 OTTAWA EDMOND CLOUTIER, C.M.G., O.A.. D.S.P. KING'S PRINTER AND CONTROLLER OF STATIONERY 1951 ISSUE ELEVEN OCTOBER - 1951

THE CANADIAN FISH CULTURIST

LIBRARI" FI 'liEi'•;Is^ AND OCEANS BIBLIOTHÈQUE PÊCHES ET OCIEANg

Published at Ottawa by The Department of Fisheries of Canada CONTENTS

PAGE The Speckled Trout Fishery of Prince Edward Island-M. W. SMITH ...... 1 A Comparison of Nylon and Cotton Gill Nets Used in the Lake Winnipeg Winter Fishery-L. C. HEWSON ...... 7 The Use of Pectoral Fin Rays for Determining Age of Sturgeon and Other Species of Fish-JEAN-PAUL CUERRIER.. 10 Results of a Bacteriological Examination of a Diseased Sucker- LEO MARGOLIS ...... 19

Requests for earlier issues of The Canadian Fish Culturist continue to be received. Unfactunately no copies of earlier issues are now available. Correspondence concerning The Canadian Fish Culturist should be addreased to the Director, Information and Educational Service, Department of Fisheries, Ottawa, Canada.

Published under Authority Of HON. R. W. MAYHEW, M.P., Miniata of Fisheries 1 THE SPECKLED TROUT FISHERY OF PRINCE EDWARD ISLAND* by M. W. Smith Fisheries Research Board of Canada, Atlantic Biological Station, St. Andrews, N.B. The speckled trout fishery of Prince Edward Island, if not unique, at least presents features which are not commonly encountered by fish culturists whose interests are with this species. An abundance of young trout in most streams, for instance, reduces stocking to a minor need in localized situations. Again, a large number of trout run from the streams into salt water, and this propensity raises special problems. Both fresh and salt water environments are involved. Prince Edward Island, the smallest province of Canada, has an area of 2,184 square miles, and is situated in the southern part of the Gulf of St. Lawrence. From its length of 120 miles and average width of 20 miles, it is evident that the stream systems are short and that in general we are dealing with small waters. The Island is a stabilized, prosperous farming community and a well-developed road system makes streams and artificial ponds readily accessible to anglers.

Character of Trout Production The excellence of trout fishing in Prince Edward Island streams, estuaries and ponds has been appreciated by generations of anglers. Statistics upon the production of trout in these waters are available, however, only for recent years. Since 1943 a creel census has been taken during each angling season (April 15- September 15) at an artificial 23-acre pond situatz!d just above the head of tide on the North Montague River, which has a course of approximately 15 miles. A small pond was originally formed on this site over 60 years ago, and the present higher level has been held since 1917. Creel census data are given in Table I and show that the yield to the anglers has fluctuated during the period of eight years from a low of 2,403 trout in 1948 to a high of 3,819 in 1946. Expressed in other ways, the annual yield has varied from 22 • 4 to 44 • 0 pounds per acre, and the average rate of capture from 1- 4 to 2-5 trout per rod-hour. The yearly average total length of the trout has remained within the narrow limits of 8- 0 to 8- 5 inches.

Table I Yield of Speckled Trout to Anglers from Montague Pond, P.E.I.

- 1943 1944 1945 1946 1947 1948 1949 1950

Number caught ...... 3,731 3,801 3,533 3,819 3,061 2,403 3,097 3,622 Number of rod•hours ...... 1,492 1,516 1,632 1,634 1,723 1,351 2,144 1,868 Number per rod•hour..... 2•5 2-5 2•2 2•3 1•8 1-8 1•4 1•9 Average total length (in.) - 8•2 8•5 8-1 8-4 8-0 8•1 8•2 Average weight (oz.)...... - 3•8 4•5 3•6 4-1 3•4 3•6 3•7 Pounds per acre...... - 40•7 44•0 37•2 34-1 22•4 30-1 36•7

*Read at the Northuut Atlantic Fisheries Conference, Portland, Maine, March 22-23, 1951.. 89480-1 2

Although a very considerable number of trout have been taken each year from the pond, the data present no consistent evidence that the anglers' catch of one year had a determinative influence upon that of a year later. Rather the continued good yields, although fluctuating, reflect the good reservoir of young trout to be found in the feeder stream, as is well illustrated by the following data. On September 11, 1944, seven seine hauls in pools of the stream, about four miles above the pond, captured 1,237 trout. Only 28 of these were over seven inches in notch length, while 633 were under 42 inches. Since only one haul was made in each pool it is to be appreciated that the captures did not represent the total number of trout present. In view of this information one might reasonably assume that a greater annual cropping of trout in the Montague Pond would not endanger the fishery. Ellerslie Brook is a small spring-fed stream whose effective length for supporting trout, even those of the year, is limited to approximately four and one-half miles. In connection with an investigation to which reference will again be made, a two-way fish trap has been held at the mouth of this brook since June, 1946. The trap has been operated throughout each year, and since April, 1947, each trout that has moved for the first time, either into or out of the brook, has been tagged. Tagging records disclose that 2,886 trout moved through the traps during the period April 22, 1947, to April 21, 1948. Over the same periods in 1948-49 and 1949-50 the numbers were 2,287 and 2,647 respectively. These data do not, however, provide information upon those trout present in the brook which did not run to sea during those periods. Summer estimates of population in 1948, 1949 and 1950 placed the number of such trout, including fish of the year, at about 20,000 for each year. Creel censuses maintained on the brook and upper part of the estuary since 1947 have shown annual yields varying from 1,086 to 1,942 trout captured at average annual rates from 1- 5 to 1- 9 per rod-hour (Table II). Table II Yield of Speckled Trout to Anglers from Ellerslie Brook, P.E.I.

Year Number Average Number per caught length (in.) rod-hour

1947. ._...... 1,141 6•9 l-5 1948 ...... 1,086 7•0 1•5

1949 ...... 1,942 6•9 1•8

1950 ...... 1,608 7•0 1•9

From our knowledge of the fishery, we believe that the production levels for trout in Ellerslie Brook and Montague Pond are quite representative of those in streams and artificial ponds of Prince Edward Island generally. Except locally, and then temporarily, we are as yet concerned with under-cropping rather than over-cropping by anglers. 3

Environmental Conditions The environmental conditions which make for such favourable habitats for speckled trout have been primarily determined (1) by the underlying geological formation and (2) by the insular position of the waters. The underlying rock formation of almost the entire island consists of Neo-Permian sandstones with calcareous cements. These sandstones have weathered to provide deep porous soils which are everywhere in evidence except in low-lying areas where humus and peats have accumulated superficially. The porous soils are conducive to spring drainage and the streams are generally spring-fed, with the result that they present relatively cool aquatic environments in summer, that their levels are well maintained throughout the warm weather, and that spawning facilities for speckled trout are good. Again because of the nature of the soils, Prince Edward Island is one of the better farming districts in the Maritime Provinces, and has justly earned the sobriquet "Garden of the Gulf". However, to sustain the fertility of the top soils, especially in the potato- farming districts, the practice of applying artificial fertilizers is wide-spread. Accord- ingly, the natural fertility of the streams and ponds is much enhanced by drainage from these cultivated lands, and results in a rich growth of aquatic plants and animals, a large proportion of the latter being trout foods. We here have an example of a bene- ficial rather than a deleterious effect upon a natural environment by man's interference. Numerous bays, often with barrier sand islands between them and the more open sea, and estuaries running well inland at the mouths of streams, are topographical features of Prince Edward Island. These protected, shallow and productive areas are apparently suitable habitats for those speckled trout that run into them from the streams and remain for variable periods of time, for those trout make good growth during the sojourn in salt water and are among the larger trout angled from the Island waters. Thus not only the favourable character of the fresh waters but also that of the brackish and salt-water inlets contribute to the quality of the trout fishery. Further contributing in no small way to the success of the young trout in the streams are the limited competition and predation by other species of fish. In many situations the fish fauna consists almost entirely of trout. In our experience the most serious competitors are the young of the Atlantic salmon. Because of their insular position no indigenous strictly freshwater fish are present in the Island waters. (The golden shiner has been introduced and beeome established in one of the few natural ponds.) Thus the fortunate combination of fertility, coolness of water, favourable spawning conditions and limited competition and predation by other species conditions Prince Edward Island streams for a high production of young speckled trout.

Problems of the Fishery It is apparent from what has already been stated that on Prince Edward Island we are not primarily faced with the common problems that so frequently beset the attempts of fish culturists to maintain and improve speckled trout angling, such as a scarcity of young native trout, serious competition and predation by other fish, infertility of waters and high temperature. Rather, the initial problems involve the management of adequate stocks of young trout toward an increase in their number and availability at suitable 4

size for angling. Pond formation presents one method of meeting these problems in management, for, as exemplified by the results of the creel census at the Montague Pond, artificial ponds created on Prince Edward Island streams usually provide good angling. Pond formation is the most direct approach to overcoming a major deficiency, namely the lack of sizable natural fresh waters. Notwithstanding its basic simplicity and directness as a means to overcome this deficiency, pond formation in turn poses other problems. As we have noted, trout run to salt water from the Island streams and they constitute the stock for a sport fishery in the estuaries and contribute to that in the fresh waters upon their return to the streams. Pond formation obviously curtails the movements of these trout upstream. Accordingly there is the problem of determining how the formation of a pond affects the trout population of a stream system as a whole-the stream and the estuary. Will the benefits accruing to anglers by forming a pond be offset by a reduction in the fishery for the sea-run individuals when these are restricted in upstream movements by dams? Also what will be the result of reducing the stream areas available to the sea- run trout for spawning, especially if pond formation is extensively applied? The reduction in spawning areas will be most serious if sea-run parents are necessary to provide sea-run progeny, but of much less significance if the sea-run group is recruited indiscriminately from the stock of young trout in the stream irrespective of parentage.

Attack on the Problems Pond formation in itself, without attempt at regulation of density of stock or in any way manipulating the pond environment, provides, as we have shown, good angling. However, it can be practised without realization of the full potentialities of such pond areas as trout producers. Further steps in management need to be explored. We have investigations currently under way in artificial ponds on Island streams to determine the most suitable density of stock for optimum production of trout of angling size. The dams are constructed so that the ponds can be drained to the original stream level and the standing crop of trout accurately assessed. Results to date from three ponds suggest that an initial density of 400 yearling trout per acre does not utilize the full trout-producing capacity of the ponds, although with this density of stock total yields (final less initial weight of trout) of as much as 29 pounds per acre have been obtained in a three-month interval from late spring until early fall. Greater densities of stock are to be tested, and the full programme for the experimental ponds envisages tests upon further enrichment of the water with artificial fertilizers and the possibility of utilizing waste from local commercial sea fisheries to augment the food supply. A programme of pond formation as a means to improve angling is complicated, as we have already intimated, by the fact that ponds restrict the movements of those trout that run to salt water and periodically return to the streams. At Ellerslie Brook the effect of pond formation upon the trout population of a system is being studied. Since 1946 a two-way fish trap has been maintained at the mouth of this small stream at all seasons of the year, and trout entering and leaving the brook are enumerated, measured and tagged. A creel census is kept of the trout that are angled. Stocks of young trout in the brook are evaluated each year. A pond will be formed when sufl•i- cient data for comparison are compiled from the unobstructed brook. 5

Fish traps at the mouth of Ellerslie Brook, P.E.I.

Simpson 's Pond, P.E.I., an artificial experimental pond used in the studies of trout production.

S9-IS0 -'' s

In an attempt to gain an understanding of the relationships between the brook and sea-run groups, progeny from these two stocks of trout have been planted in Ellerslie Brook as fish of the year and as yearlings, after being marked differently by fin-clipping. As yet these planted trout have not entirely moved through the population of the system, and the data upon them are therefore incomplete. For the present it can be reported that the progeny from both parentages have run from the stream. Thus apparently the sea-run group can be recruited from a brook stock that has not been to salt water for many generations, but it is yet to be determined how effectively this may be realized. In the programme at Ellerslie Brook the anglers' catch was one of the more important criteria by which the effects of pond formation upon the trout stock were to be gauged. We have noted that without pond formation the yield to the anglers has varied from 1,086 to 1,942 trout over a four-year period, and the rate of capture from 1- 5 to 1- 9 per rod-hour. Obviously the establishment of a reasonably constant level for comparative measurements of fish production in nature is difficult, even, as in this case, in a small stream. The lesson is clear that if worthwhile fish management proce- dures are to be developed they must rest upon data obtained over a sufficiently long period to delimit natural fluctuations. 7

A COMPARISON OF NYLON AND COTTON GILL NETS USED IN THE LAKE WINNIPEG WINTER FISHERYI) by L. C. Hewson Central Fisheries Research Station, Winnipeg, Manitoba

The introduction of nylon gill nets to the fishery on Lake Winnipeg during recent seasons has aroused considerable interest and some controversy among fishermen, and others. Various opinions regarding their efficiency have been expressed. Lawler (1950) suggests that in the gill net fishery for lake whitefish on Lake Erie, nylon netting is about three times as efficient as linen. Some fishermen claim that the nylon gill net takes a greater number of small fish than an equivalent mesh size in a cotton gill net. Others feel there is no essential difference in size of fish taken, but that a nylon gill net will catch more fish than a comparable cotton gill net. Still others believe there is no real difference at all. During January and February of the 1950-51 winter fishing season on Lake Win- nipeg, Fisheries Research Board of Canada personnel of the Central Station had occasion to record data pertinent to this question. The data recorded were from the gill nets lifted by commercial fishermen fishing at various points on the ice throughout a distance of about 120 miles. For convenience, this distance was divided into three adjoining areas of approximately equal size. The fishermen from whose nets the data were taken were selected at random.

Record Weight of Each Fish Each gill net was lifted singly during the winter fishery. As it was being lifted a record of the weight of each individual fish was taken. The fisherman was asked to report as accurately as possible the length of the gill net as well as the mesh size and net depth. The material from which the netting was made was also recorded. Only those data from nylon and cotton gill nets reported as three-inch mesh were used in this paper. The bulk of the data was collected from gill nets which were fished under similar conditions. In only a few cases was it possible to record data from adjoining cotton and nylon gill nets. An examination of Table I shows that in each of the areas the average weight of individual fish is generally greater in the nylon nets. This difference is evident probably because cotton nets tend to shrink with usage. As shown in Table 1, Area 1, cotton nets caught considerably more fish per 100 yards than the nylon nets. The figure for availability (i.e. catch'per unit effort) for the cotton nets is probably misleading as it was computed on only 70 yards of gill net for the whole of the area, as compared with 930 yards of nylon gill net. In Area 2 the

(1) Received for publication May 1951. 8943U-2+} 00

Table I

The average round weight of species and the average availability of representative samples of fish from nylon and cotton gill nets of three•inch mesh used in the Lake Winnipeg winter commercial fishery during January and February, 1951. The number of individuals is shown in parentheses.

Area 1 Area 2 Area 3 All areas cotton nylon cotton nylon cotton nylon cotton nylon

Sauger 0•64 0•68 0•56 0•60 0•56 0•59 0•56 0•63 (33) (295) (652) (127) (652) (197) Average weights of sFecies (lbs.) Pikeperch 1•05 0•96 0•79 0•80 0•68 0•77 0•72 0•83 (10) (183) (211) (179) (547) (269)

Burbot ...:...... 1•17 1•47 1•72 1•32 1•05 1•35 1•16 1•44 (41) (173) (54) (27) (11) (10) ------_^- ^-- Sauger ...... 30•0 21•5 11•0 14•5 5•5 11•5 7•5 15•5

Pikeperch ...... 15•0 19•0 5•0 27•5 5•5 19•5 5•5 21.0 Average catch per 100 yards of gill Burbot ...... 68•5 27•5 2•0 7•0 0•18 1•0 1•0 12•0 net (lbs.) - Otherspecies ...... 18•S 11•0 5•0 12•5 1•5 2•5 2•5 7•5

All species ...... 132•0 78•5 23•0 62•0 13•0 34•5 17•0 57•0 9 comparisons are based on 3,316 yards of cotton gill net and 516 yards of nylon. In Area 3, 6,420 yards of cotton gill net and 1,046 yards of nylon were used in determining the availability. In all areas, the availability of all species is roughly three times as great for nylon gill nets as for cotton ones. Total yardage for all areas is 9,806 for cotton, and 2,492 for nylon gill nets. Regarding working characteristics, the fishermen reported that during very frosty weather nylon gill nets were more difficult to clear than the cotton ones. On the other hand, cotton gill nets became occluded by a heavy phytoplankton pulse much more quickly than did the nylon gill nets. This appeared to be an important factor in the relative size of the catches. It seems clear that the three-inch mesh nylon gill net is considerably more efficient in the Lake Winnipeg winter fishery than the three-inch mesh cotton. The average size of fish taken in each is similar.

Literature Cited LAWLER, G. H. 1950. The use of nylon netting in the gill-net fishery of the Lake Erie whitefish. Fish Culturist, No. 7: 22-24. Canadian lo

THE USE OF PECTORAL FIN RAYS FOR DETERMINING AGE OF STURGEON AND OTHER SPECIES OF FISH by

Jean-Paul Cuerrier(1) Canadian Wildlife Service, Ottawa, Canada I Until the last few years, little has been written in the scientific literature of North America on the sturgeon, which were for a time of great economic importance in many parts of Canada and the United States. Ryder (1890), Harkness (1923) and Greeley (1937) are probably the only authors who so far have published papers to which stu- dents, investigators and administrators may refer for information. At present, biologists are witnessing activities and research in connection with various species of sturgeon and, as a result, a considerable amount of new information is, or will be, on hand to increase our knowledge of this enigmatic fish and to estabksh basic principles for its best utilization and conservation. Investigators of this continent who, to the writer's knowledge, are actively interested in some phases of the biology of the sturgeon may be listed as follows: I. J. Donaldson, Corps of Engineers, Oregon, studying the growth and migration of the Pacific Coast sturgeon; Dr. J. Greenbank, Wisconsin Conservation Department, working on the commercial fisheries for the Mississippi sturgeon; Dr. W. J. K. Harkness, Chief, Fish and Wildlife Service, Ontario, supervising the commercial fisheries for lake sturgeon in Northern Ontario and working on a voluminous manuscript on the early stages and other phases of the life history of lake sturgeon; Dr. V. D. Vladykov and G. Beaulieu, Department of Game and Fisheries, Quebec, studying morphological characteristics, food and migration of the two species of sturgeon inhabiting the lower St. Lawrence River; and the writer, who, until recently, was engaged in the study of commercial fisheries, growth, food, gonad maturation and migration of the lake sturgeon in the Montreal region and the Ottawa river. The collection of records of recaptures of tagged sturgeon is being continued by G. Prévost, Provincial Biological Bureau, Department of Game and Fisheries, Quebec. The most essential data for guidance in establishing adequate management and proper legislation governing any fishery are size, age, the rate of growth, the rate of development of the gonads and the spawning behaviour of the species of fish concerned. For the lake sturgeon, Acipenser fulvescens Raf., data on age and growth were first obtained by examining otoliths as described by Harkness (1923) in his study of this species in Lake Nipigon, Ontario. In order to carry on a similar study, about 300 samples of otoliths of sturgeon were collected on Lake St. Peter (St. Lawrence River) during the summer of 1945. This method was not found satisfactory, and study of the material collected was delayed by experiments in sectioning the otoliths.

(1) Investigations on sturgeon under the auspices of the Department of Trade and Commerce, Province of 4uebec, were carried out by the author prior to July, 1949, bcfore he joined the Canadian Wildlife Service. 11

In the spring of 1947, while the author was preparing the programme and the organization for a general survey of the sturgeon fisheries in the St. Lawrence River and a collection of material and data to study the biology of this species, a visit was paid to the Institute of Biology of the University of Montreal by Dr. Georges Roussow, a distinguished Roumanian biologist, who had recently arrived in this country. In the course of general discussion, Dr. Roussow informed us of his experience with sturgeon and mentioned the technique used by workers of Eastern Europe to determine its age and study its rate of growth. This technique, which he himself (Roussow, 1938) and his chief at the "Institut National Zootechnique" of Roumania, Dr. Th. Negulesco (1934), had used in studying the Sterlet, A. ruthenus, was based on cross-sections of marginal rays of the pectoral fins. Specimens of sturgeon were taken from the fish collection room, cross-sections were made and ages were determined to our satisfaction. Roussow (1947) discussed the technique in a brief paper presented at the Société Canadienne de Biologie, Montreal. This information led the writer to undertake an extensive collection of fin rays and search in foreign bibliography for information on various methods used for determination of age of sturgeon. The bibliography on the subject has brought to light some material which might be useful for other workers interested in this subject. This paper is intended to summarize the bibliographical material collected by the author on methods for determination of age of sturgeon, to discuss the technique for preparing and examining the marginal rays of pectoral fins, and to illustrate by figures cross-sections obtained from pectoral fin rays and pectoral spines of various species of fish. Methods for Determination of Age of Sturgeon As far as could be found out from various papers and bibliographies examined, Arnold (1911) is probably the first author who determined the age of sturgeon and studied the growth of representatives of Acipenseridae. For this study, the claviculum bones were used by Arnold, and later by Soldatov (1915). In 1916, Kleer or Clair published a paper on age of sturgeon determined for the first time by the cross-section of marginal rays of the pectoral fins and also by the caudal fulcra. In 1932, Derjavin published a paper on the biology of the Sevriuga (A. stellatus); his age determinations were made from the cleithrum bones. It may be mentioned here that cleithrums collected from lake sturgeon of the St. Lawrence River very frequently showed the formation of large cavities in the centre of the bone, which would have limited their use for age determination. Such resorption has been noted by Chugunov (1925). In 1923, Harkness published a paper on age and growth of the lake sturgeon from Lake Nipigon, Ontario. His growth study is based on examination of otoliths, contained in an internal ear sac, the saccula. Harkness is quoted as the first investigator to use the otoliths for the determination of age of sturgeon. D'Ancona (1924) used for the determination of age of sturgeon the scutes or plates which are present along the back sides and belly of the Acipenseridae. This technique could not be used with lake sturgeon except among young individuals because the scutes show degeneration and disappear almost completely as the adult stage is reached. 12

The same year, 1924, Holzmayer published a paper on the marginal rays of pectoral fins and their use for determining age of sturgeon. Reference to this author will be made later on. Chugunov (1925), who quotes Kleer's paper, used the pectoral fin rays and the fulcra to determine the age and study the growth of sturgeon collected by the Asov Scientific-Industrial Expedition. In his 1925 paper, this author described briefly the technique for the preparation of cross-sections of pectoral fins. All subsequent investigations carried on by European biologists regarding growth of various species of sturgeon were based on examination of cross-sections of marginal rays of the pectoral fins: Petrov (1927), Probatov (1929), Negulesco (1934), Menshikov (1936), Roussow (1938), and Classen (1944), who also used dorsal scutes. Most of these authors, particularly Classen, have presented in their papers illustrations of cross- sections of "marginalia", as they are called by Classen. On this continent, Bajkov (1930), Greeley (1937) and Schneberger and Woodbury (1944) have studied the growth of various species of sturgeon by using the otoliths as did Harkness (1923). In the author's investigations since 1947, anterior marginal rays of pectoral fins of about 2,0001ake sturgeon were examined; part of this material has been discussed in manuscript reports submitted to provincial authorities. Some of these reports are being revised for publication (Cuerrier, 1949 (a); Cuerrier and Roussow, 1951). A brief paper on the growth of lake sturgeon with an illustration of a cross-section of the "marginalia" was published in 1949 (Cuerrier, 1949 (b)). For illustrations of sections of pectoral fin rays of Pacific Sturgeon, one may refer to the Oregon State Game Com- mission Bulletin, November, 1949, and to Popular Mechanics, December 1950. Lea Dahl's formula has been adapted for sturgeon and utilized to calculate the size of the fish at any given year of its life. Derjavin (1922), Roussow (1938) and particularly Classen (1944) have studied the relation between the annual growth of cleithrum bones or of the marginal rays and the size of the fish at the time of the formation of a year-mark. Classen presents in his paper many tables and illustrations on age and length relationship based on calculated growth and indicates in the illustrations how the measurements are made. For fish provided with scales, many authors have proved the validity of the use of the scales for determining age. Regarding the marginal rays, little such work has been done. The method, however, is not taken for granted. Holzmayer (1924) made a control age determination of preserved material of Sterlet (A. ruthenus) raised by A. A. Ostrooumov (1925), who studied the periodicity in the rate of growth of Sterlet reared in captivity during as long as, in one case, 10 years and 4 months. Cross-sections of the marginal rays of the pectoral fin showed a number of annual marks corresponding to the recorded age of the fish. Indirectly, Roussow (1938) and Classen (1944) have been able to confirm the age determinations obtained with fin-ray sections by comparing average lengths obtained by this method with averages obtained from lengths calculated tl according to age. The calculated lengths corresponded to the measured lengths of fish of known age. 9 A further attempt is being made to confirm the validity of the method of using pectoral fin rays for determination of age of sturgeon. During 1947 and 1948, several hundreds of lake sturgeon caught by commercial fishermen were tagged and released in 13

the St. Lawrence River after the anterior portion of the marginal ray of one pectoral had been collected. It is hoped that some of the individuals will be recaptured in order to compare the reading obtained from the portion collected with the reading obtained from the marginal ray of the other pectoral fin at the time of recapture.

The Pectoral Fin Marginal Rays Method While the collection of otoliths, operculums or other bones from sturgeon requires I much time and also spoils the appearance of the fish for market, the pectoral fins can be secured without trouble or deterioration of the specimen. I Details concerning collection, sectioning and preparation of the material for determination of age based on pectoral fin rays are given by Chugunov (1924) and by Negu- lesco (1934). As these publications are not readily available, the technique applied during our investigations since 1947, without having on hand at that time the two papers mentioned above, will be discussed here. The pectoral fin of one or, preferably, both sides is cut with a knife at the articulation with the cartilaginous basal piece. Usually, only the first few rays are cut from the fish or retained from the entire fin already collected. Then a small hole is drilled in the sample, a card is filled with the usual data and the fins and the card are tied together with a brass wire. The samples are hung to dry in the sun, because they have to be dried perfectly before further processing. When dried, the sample is placed between the jaws of a vice, the marginal ray being up. Then sections are obtained by using a single thin blade saw adapted to a small hand jigsaw. For best results, the saw should have about 70 teeth to the inch; such saws are of a type usually used by jewellers. Chugunov and Classen have suggested and used two saws fastened parallel to each other and divided by a thin plate in order to obtain sections of about 0•5 mm. thick. But I personally prefer a single saw; after some practice, sections of 0•5 to 0•3 mm. and even less can be obtained easily. Sections must not be too thin, because then they would be too transparent. For special purposes, the sections can be polished on a fine-grain carborundum plate as designed by Mr. I. J. Donaldson of Oregon; but this operation was found unnecessary for routine examination and even for recording on photographic plates. The sections are made by cutting perpendicularly near the base of the ray when perfectly dry, at about ;-inch from its articulation. If made too far from this point, interior rings laid down during the first years of the life of the fish are lost. When sections are to be studied, they are placed on a glass slide in a few drops of pure glycerine. Water, alcohol or Canadian balsam can be used instead of glycerine, but the latter gives much better results. The main point is to obtain the best differential transparency of the zones which exist on the cross-sections. If sections are too thin, the penetration of the glycerine becomes uniform and makes them entirely transparent. With a section of 0- 3 to 0- 5 mm. the glycerine will infiltrate slowly into some zones and rapidly into other zones. Permanent mounting was not made, because within a i few months the differentiation between zones is mostly lost and the sample is almost uniformly transparent. To keep samples for further checking, the sections were washed in hot water, passed from diluted alcohol to absolute alcohol, dried and then stored in their respective vials. 14

PLATE I

Sections of Marginal Pectoral Fin Rays of Lake Sturgeon

Figure 1. Lake St. Francis, July 9, 1947. Fork Figure 2. Lake St. Peter, June 18, 1948. Fork length, 28 . 5 inches; weight, 6 pounds; age, 9 years. length, 31 • 5 inches; weight, 8 pounds and 11 ounces; age, 17 years.

Figure 3. St Francis River (Lake St. Peter region), Figure 4. Lake St. Peter, May 16, 1948. Fork May 27, 1947. Fork length, 4S-5 inches; weight, length, 42 inches; weight, 23 pounds; age, 26 years. 25 pounds; age, 22 years. I 15

PLATE II Sections of Marginal Pectoral Rays of Other Fish

Figure 2. Rocky Mountain Whitefish pectoral fin Figure 1. Lake trout pectoral fin ray section-Lake ray section-Lake Minnewanka, Banff National Minnewanka, Banff National Park, July 9, 1950. Park, July 9, 1950. Fork length, 14-5 inches; weight, length, 29 inches; weight, 12 pounds; approxi• Fork 12 ounces; approximate age, 9 years. mate age, 10 years.

Figure 4. Channel Catfish pectoral spine section Figure 3. Bullhead pectoral spine section-Sample River, Lake Deschenes, June 15, 1949. skeleton collected at Point Pelee -Ottawa from part of a length, 13 inches; weight, 15 ounces; approxi- Approximate age, 4 years. Fork National Park. mate age, 10 years. 16

Under the binocular microscope with low magnification and with transmitted light, the observer will see some wide opaque zones alternating with narrow clear zones, the former corresponding to summer growth and the latter to winter growth. The summer zones or rings, being rich in what is presumed to be a deposit of calcium- containing material, are not easily penetrated by the glycerine, and appear dark, as the light does not pass through. The rings observed on the anterior ray of a pectoral fin can be noted on the subsequent pairs of rays, but these rays are much smaller and the rings are not usually so distinct. The figures, illustrating cross-sections, which are presented in Plate I were obtained by projecting the sample on a glass photographic plate using a projector for 35-mm. films. Prints and transparencies are then made from this negative. If a section is projected directly on a photographic paper, as was done by Classen, the zones will appear as if the sections were examined under a binocular microscope by reflected light; the narrow zones will be printed black and the wide zones white. Photographs repro- duced in Plate II were taken through a microscope. The marginal rays of the pectoral fins of sturgeon are presumably formed by successive deposits of calcareous material on the surface of the ray. The deposits probably vary according to the metabolism of the animal. The formation and development of the bony rays are assumed to be similar in nature to those of the membrane bones of the skull, where the osseous tissue is derived from connective tissue. The wide zones which can be seen on the accompanying photographs are probably the result of an abundant formation of connective tissue during the summer, converted later into bone tissue; the narrow zone would correspond to the period of metabolic inactivity during the winter period, when only a small amount of connective tissue and subsequent bone tissue is formed. The tissue being more compact in the first region than in the second, the glycerine penetrates the second region more rapidly and gives differential transparency of zones, or rings. Plate I illustrates sections of marginal rays of sturgeon of different ages. The rings are very clear and the interpretation of the sections does not require additional comment. Those who have Classen's paper on hand will note a difference in interpretation of the first annual ring corresponding to the first winter. Classen differentiates between the centre of ossification and the zones for the year 0, for.year 1, and for subsequent years. According to our interpretation, the centre of ossification is followed by the first winter ring, year 1, then by the second winter ring, etc. Our interpretation appeared to be in accordance with figures presented by Negulesco (1934) and Menshikov (1936).

Application of the Fin Technique for Other Species of Fish The Progressive Fish Culturist, January, 1950, reprinted a paper published in 1946 by a Russian scientist, E. G. Boyko, on age determination among fish. The author indicates that the pectoral fin method is applicable to species of fish with soft rays as well as to species with bony rays and spines. He describes the technique for preparation of sections as used in the Don-Kuban experimental fishery station, where scales were utilized for age determination. It was found that the annual rings were more distinctly expressed on fin rays than on scales. 17

Attempts are being made by the Canadian Wildlife Service to utilize pectoral fin rays of trout and other species of fish for determining age. During the summer of 1950, pectoral fins of lake trout, rainbow trout, eastern brook trout, cutthroat trout and other species of fish inhabiting National Park waters were collected. The preliminary tests showed that the present method applied in the case of sturgeon would have to be improved for other fish, due to the small size and fragility of the pectoral fin rays. Samples would have to be embedded and the sections cut with a finer saw blade. However, some sections cut from fins of various species of fish showed relatively clear rings. The readings from these sections gave figures within the range of ages for the sizes of the specimens as found in the literature. So far, the specimens of the collection which have given the best samples of fins had scales rather difficult to read. Samples of fish with pectoral spines, such as bullhead from Point Pelee National Park and channel catfish from the Ottawa River have shown very clear rings on the pectoral spines. In the issue of the Missouri Conservationist for August, 1945, a photograph illustrates the collecting of spines of catfish. A Missouri biologist is at present studying the growth of bullheads by using the vertebrae as indicators. Other biologists investigating freshwater and marine species of fish are planning to use the pectoral fin rays, in the hope of replacing present use of otoliths. There is no doubt that the fin technique will never replace the scales for age study among species such as bass, yellow perch, yellow pikeperch, sunfish and salmon. For many species without scales or with small or minute scales, the recognition of the use of pectoral fin rays as a satisfactory method of age determination will simplify the study of the large quantity of material that is required to reach acceptable averages and adequate conclusions.

Literature Cited

ARNOLD, I. 1911. On the determination of growth of fish. Fishery report. 26. BAJKOV, A. 1930. Fishing industry and fisheries investigations in the Prairie Provinces. Trans. Amer. Fish Soc. 60: 215•237. BOYKO, E. G. 1946. Age determination in fishes, based on examination of finray sections. Comptes Rendus, Academy of Science, Moskow, New Series 53 (5): 483-484. CHUGUNOV, N. L. 1925. On the methods of age determination in Sturgeon. (From Asov Scientific Industrial Expedition.) Bull. of Fisheries Economy. 11: 33. CLASSEN, T. E. A. 1944. Estudio Bio-Estadistico del Esturion o Sollo del Guadalquivir (Acipenser sturio L.). Instituto Espanol de Oceanografia, Madrid. Trabajo numero 19: 5270. CUERRIER, J. P. 1949. (a) Observations sur l'esturgeon de lac (Acipenser fulrescens Raf.) d-ns la région du lac Saint-Pierre au cours de la période du frai. Thèse. Manuscrit. Université de Montréal, Mont- réal. CUERRIER, J. P. 1949. (b) L'esturgeon de lac; Age- croissance-maturité. Chasse et Pêche (Montréal) 1 (6): 26, 1949. CUERRIER, J. P. ET G. ROUSSOW. 1951. Age and growth of Lake Sturgeon from Lake St. Francis, St. Lawrence River. Report on material collected in 1947. Canadian Fish Culturist. (10): 17-29. D'ANCONA, U. 1923. Data per la determinazione dell eta a per lo studio dell'accresciments negli storio- ni. Atti Reale Accd. Nazionale dei Lincei, Serie Quinta. 22 (3): 132-137. DERJAVIN, A. N. 1922. The stellated Sturgeon (Acipenser stellatus Pellas), biological sketch. Bull. of Ichthyological Laboratory of Baku. 1: 1-393. GREELEY, J. R. 1936. Fishes of the area with annotated list. A biological survey of the Lower Hudson Watershed. Supp. 26th Ann. Rep. N.Y. State Biol. Survey No. 11: 43-103. HARKNESS, W. J. K. 1923. The rate of growth and the food of the Lake Sturgeon (Acipenser rubicundus). Univ. Toronto Studies. Publ. Ont. Fish. Res. Lab. 18: 15-42. HOLZMAYER, H. 1924. Zur Altersbestimmung der Acipenseriden. Zool. Anzeiger. Bd. LIX. KLEER, V. 1916. Some data on the age determination of fishes by bones. Bulletin of Fishing Indu:try. Vestnik rybopromyshlennosti. No. 3. 13

MENSHIKOV, M. I. 1936. Contribution to the biology of Acipenser bath and Acipenser ruthenus in the River Irtysh. Sci. Mem. of the M. Gorky State University of Perm. 2 (1): 41-64. NEGULESCO, TH. 1934. Détermination de l'âge et de la croissance des Acipenseridae. Ann. Inst. Nat. Zootech. de Roumanie. 3: 254-269. OSTROOUMOV, A. A. 1911. Périodicité de la croissance des sterlets. Travaux de la Soc. des Na. de Kazan. 43 (6). PETROV, V. V. 1927. Material on study of growth and age of Caspian Sturgeon. News Dept., Bureau of Applied Ichthyology. 6 (2). PROBATOV, A. N. 1929. Age of the Aral Sea Sturgeon (Acipenser nudiventris). Bureau of Applied Ichthyology. Bull. 9 (2): 154-162. ROUSSOW, G. 1938. Contribution à l'étude de l'extérieur et de la croissance de l'Acipenser ruthenus L. Ann. Inst. Nat. Zootech. de Roumanie. 6: 248-264. ROUSSOW, G. 1947. Application de la méthode des coupes transversales du premier rayon de la nageoire pectorale pour la détermination de l'âge chez l'esturgeon de lac (Acipensei fulvescens Raf.). Soc. Biol. de Montréal. Comptes rendus. Revue Can. de Biol. 6 (2): 362 (titre seulement). RYDER, J. A. 1890. The sturgeons and sturgeon industries of the eastern coast of the United States, with an account of experiments bearing upon sturgeon culture. Bull. U.S. Fish. Comm. 8: 231-328. SCHNEBERGER, E. AND L. A. WOODBURY. 1944. The lake sturgeon, Acipenser fulvescens Rafi- nesque, in Lake Winnebago, Wisconsin. Trans. Wisc. Acad. Sci., Arts, and Lett. 36: 131-140. SOLDATOV, V. K. 1915. Étude sur les Acipenseridae d'Amour. Matériaux pour l'étude de la Pêche de la Russie en 1914. 3 (12). Petrograd. 19

RESULTS OF A BACTERIOLOGICAL EXAMINATION OF A DISEASED SUCKER by Leo Margolis

Graduate Assistant, Institute of Parasitology, McGill University, Macdonald College, Que.

A specimen of the common sucker (Catostomus commersonii commersonii Lacé- pede), found close to death, floating on the surface of the Ottawa River near Ste. Anne de Bellevue, was brought in for examination by Dr. L. P. E. Choquette of the Institute of Parasitology, McGill University. Five superficial skin lesions, consisting of haemorrhagic areas about one centimeter in diameter; were visible on various parts of the body of the fish. The scales were either lost or damaged in the vicinity of the lesions. The underlying muscle tissue was not affected. Gross pathological changes were not present in the internal organs or the gills. Microscopic examination of material scraped from the lesions revealed a large number of motile, Gram-negative rod-shaped bacteria, 0- 6-0.8/A by 1-31A, mostly arranged in pairs. This finding suggested that the condition was possibly of bacterial origin. Aerobic cultures on beef-heart extract nutrient agar were made from material from the lesions and underlying muscle and from the heart blood. The cultures from all the lesions yielded a practically pure culture of a bacterium which was identical, morphologically, with the organisms seen in the direct smears from the lesions. A mixed culture of three species of bacteria, with the predominance of one species which was proved to be identical with the organism isolated from the lesions, was obtained from the heart blood. No growth was obtained on plates inoculated with material from the muscle underlying the lesions. The organism isolated from the lesions and also found in the heart blood, had the following characteristics: Morphology: Straight rods with parallel sides and rounded ends, 0•6-0•8µ by 1-3µ, occurring mainly in pairs but also singly. Motile, with peritrichous flagella. Gram-negative. Agar colonies: Circular, smooth, entire, low convex, translucent, glistening, buff- gray Agar slant: Moderate, filiform, glistening, buff-gray. Nutrient broth: Turbid, with delicate pellicle and sediment. Gelatin stab: Liquefaction. Litmus Milk: Peptonization. Litmus reduced. Fluid becomes yellowish and translucent. Nitrites produced from nitrates. Indole is produced. Hydrogen sulphide is not formed. Growth in Koser's citrate medium. Methyl red test negative. Voges Proskauer test positive. Slight production of ammonia from urea.

Financial assistance for the research was given by the National Research Council of Canada. 20

Catalase is produced. Glucose +, galactose-{- , mannose +, lactose -}- (slow), starch +, glycerol +, mannitol +, inulin + (weak), sorbitol + (weak), salicin -, dulcitol -. (+ =fermentation with production of acid and gas: - =no fermentation.) Good growth at 25°C. and 37°C. but more rapid at the higher temperature. From its characteristics it is evident that the organism belongs to the Family Enterobacteriaceae Rahn. The slow fermentation of lactose suggests placing it in the genus Paracolobactrum Borman, Stuart and Wheeler. Of the species of this genus listed in Bergey's Manual of Determinative Bacteriology (Breed et a 11948), the organism isolated in this work most closely resembles Paracolobactrum aerogenoides Borman, Stuart and Wheeler, which is described as having the s2me characteristics as Aerobacter aerogenes (Kruse) Biejerinck, and Aerobacter cloacae (Jordan) Bergey et al, except for consistently delayed fermentation of lactose. The bacterium isolated from the sucker differs from Paracolobactrum aerogenoides mainly in being proteolytic, that is, liquifying gelatin rapidly and peptonizing litmus milk. It also reduces the litmus dye, a property not possessed by Paracolobactrum aerogenoides. In addition to these differences, other minor discrepancies occur in fermentation reactions and growth appearance on nutrient agar. The organism will be referred to in this paper as Paracolobactrum sp. The other two organisms isolated from the heart blood were motile, Gram-negative rods of smaller diameter than Paracolobactrum sp. Identification of these organisms was not attempted as they were shown experimentally to be non-pathogenic for goldfish (Carassius auratus (Linnaeus)) and yearling speckled trout (Salvelinus fontinalis fontinalis Mitchell). As the sucker was dead for about two hours before being examined, these two organisms were probably intestinal bacteria which invaded the blood stream after the death of the fish. Paracolobactrum sp. was isolated from the Ottawa River water near Ste. Anne de Bellevue and also from the intestines, but not in predominating numbers, of apparently normal healthy suckers taken from the river.

Experimental Preliminary pathogenicity tests of the three cultures isolated from the heart blood and one of the Paracolobactrum sp. cultures recovered from the lesions were carried out on goldfish and speckled trout, as these fish were readily available at these laboratories. One tenth of a cc. of an 18-24 hour broth culture at 25-28°C. of each of the cultures was inoculated subcutaneously into each of four goldfish, kept in pairs in well aerated one or two litre beakers of water. As a control, four fish were inoculated with sterile broth. The eight fish inoculated with Paracolobactrum sp. died in from 18 hours to five days. Small haemorrhagic lesions, one to three mm. in diameter, involving only the superficial skin layers were visible at the sight of inoculation in six of the fish. The two goldfish which died within 24 hours after inoculation showed no lesions. Paracolo- bactrum sp. was isolated from the lesions, when they occurred, and heart blood. All other goldfish used in this experiment were still living and apparently in healthy condition two months after inoculation, when these fish were replaced in their regular aquaria. Similar pathogenicity tests and controls were carried out with yearling speckled trout, except that 1/5 cc. of culture was used as the inoculum and two trout were 21 used with each culture and with the control. The trout inoculated with Paracolo- bactrum sp. died within 24 hours without visible lesions. Paracolobactrum sp. was isolated in pure culture from the heart blood. Trout inoculated with cultures other than Paracolobactrum sp. or with sterile broth showed no signs of illness one month after inoculation, when the experiment was terminated. Paracolobactrum sp. was never found in the intestine or slime of goldfish or trout kept at the Institute of Parasitology for many months. Further tests with Paracolobactrum sp. showed that goldfish inoculated subcutaneously with doses of 1/10 cc. of a 24-hour broth culture, incubated at 25-28°C., of this organism always died in from one to six days. No external lesions were visible in those fish which died within 24 hours. The goldfish which died between the second and sixth day subsequent to inoculation of the organism, all showed haemorrhagic skin lesions with loss of scales, at the site of inoculation. The lesions varied in size from two mm. to twelve mm. in diameter, the larger lesions occurring on those fish which survived the longest time. Some of the fish which survived for three to six•days showed slightly blood-stained peritoneal fluid. Paracolobactrum sp. was always isolated from the heart blood, peritoneal fluid and the lesions when they occurred. Subcutaneoûs inoculations of goldfish with 1/100 cc. (1/10 cc. of a 1/10 dilution) of a 24-hour broth culture at 25-28°C., of the test organism always failed to kill the fish. Approximately one-third of these fish developed skin lesions at the site of inoculation, between the third and fifth day after being inoculated. Paracolobactrum sp. was isolated from the lesions, whicfi eventually healed. Trout inoculated subcutanzously with dosz!s of the organism in 1/10 cc. to 1/5 cc. amounts of 24-hour broth cultures all died in from one to three days. There were no visible lesions on the body nor did the internal organs show any obvious macroscopic pathological changes. Paracolobactrum sp. was isolated from the heart blood and peritoneal fluid. Doses of 1/100 cc. or less of a 24-hour broth culture of the organism appeared to have no effect on the trout, when inoculated subcutaneously. All attempts to infect goldfish or yearling speckled trout by adding the test organism to water containing healthy fish, to water containing fish which had been experimentally injured at the body surface or by pouring a 24-hour broth culture on fish with experimentally produced skin lesions, failed. The Seitz-filtered broth cultures (bacterla free filtrate) of a one-day or one-week old culture did not prove toxic for goldfish or trout upon subcutaneous inoculation, in doses up to 1/10 cc. for goldfish and 1 cc. for trout.

Discussion The cxpcrimental results indicate that infection with Paraeolobaetrum sp. was probably the cause of the death of the sucker. However, the organism does not appear to be highly pathogenic, as doses of 1/100 cc. of 24-hour broth cultures were not lethal for either goldfish or trout when injected subcutaneously. Evidence for the low pathogenicity of this organism is found in the fact that although the organism was found to be fairly common in the Ottawa River water and in the intestines of healthy fish from the same river, only one sucker was found to be infected. 22

It appears that Paracolobactrum sp. is capable of living in the intestine of fish without causing disease, and is normally not pathogenic, but may produce infection under certain conditions which weaken the fish or if the fish has been injured previously. This potential pathogenicity for fish is a phenomenon well known with other water organisms (Williamson 1929). Stuart et al (1942) have suggested, in discussing gastro- intestinal infections of man, that "the paracolon bacteria lack invasiveness and that some predisposing factor for the host or massive infection is necessary before the invader can become sufficiently established to produce symptoms". This statement appears to be corroborated in this investigation. There are two possible routes by which Paracolobactrum sp. may have gained entrance to the blood stream, namely, the intestine and skin abrasions. The organism, which was shown to be present in the intestine of apparently healthy fish, may have invaded the blood stream via the intestine, if the vitality of the fish had been lowered due to some other cause. The lesions would then have been secondarily produced by organisms eséaping from small peripheral blood vessels. However, there was no evidence of an enteritis, which it seems apparent, would have been a precursor to the generalized infection if the blood invasion took place via the intestine. The other possibility is the invasion of the blood stream through small abrasions in the skin, which eventually developed into the characteristic lesions. The inability of the organism to infect goldfish or trout with experimentally produced skin lesions does not support this hypothesis, but the development of lesions in the goldfish, similar to those found in the sucker, upon subcutaneous inoculation of large doses of Paracolo- bactrum sp. and the nature of the lesions is evidence for this hypothesis. The similarity of the lesions in the goldfish and in the sucker indicate that the skin lesions of the sucker were a direct result of the infection. Experimental evidence indicates extremely low invasive power of Paracolobactrum sp. and it does not seem likely that the organism penetrated intact skin of the sucker.

Summary A diseased sucker, showing superficial haemorrhagic skin lesions, with loss of scales at the sites of the lesions, was retrieved from the Ottawa River near Ste. Anne de Bellevue. An organism resembling Paracolobactrum aerogenoides Borman, Stuart and Wheeler was isolated in practically pure culture from the lesions and as the predominating organism of a mixed culture from the heart blood. The organism is refcrred to as Paracolobactrum sp. Paracolobactrum sp. experimentally proved to be pathogenic for goldfish and speckled trout upon subcutaneous inoculation. Doses of 1/10 cc. were always fatal for both the trout and goldfish. Doses of 1/100 cc. did not kill goldfish or trout but approximately one third of the goldfish inoculated showed haemorrhagic skin lesions with loss of scales. Cultures of Paracolobactrum sp. added to water in which were kept healthy fish or fish with artificially produced skin lesions did not produce infection. Pouring the culture on fish with experimentally made skin lesions also failed to infect the fish. 23

The organism does not produce an evident exotoxin. The possible routes of entry of the organism into the blood stream of the sucker and the pathogenicity of Paracolobactrum sp. are discussed.

Literature Cited

BREED, R. S., MURRAY, E. G. D. and HITCHENS, A. P. Bergeÿ s Manual of Determinative Bacteri- ology, 6th Edition, p. 460. Williams and Wilkins Co., Baltimore. STUART, C. A., WHEELER, K. M., RUSTIGIAN, R., AND ZIMMERMAN, A. 1942. Bio- chemical and Antigenic Relationships of the Paracolon Bacteria. J. Bact. 45; p. 113-114. WILLIAMSON, I. J. F. 1929. A study of Bacterial Infection in fish and certain other lower vertebrates. Fishery Board for Scotland, Salmon Fisheries, 1929, No. 11, His Majesty's Stationery Oflice, Edin• burgh, pp. 9-11 and 24-27. OTTAWA EDMOND CLOUTIER, C.M.G.. O.A., D.S.P. RING'S PRINTER AND CONTROLLER OF STATIONERY 1951