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Sea Age at Maturity for Atlantic Salmon, Salmo salary in North America
R.A. Myers, J.A. Hutchings
Science Branch Department of Fisheries and Oceans P.O. Box 5667 St. John's, Newfoundland A1C 5X1
Department of Biology Memorial University of Newfoundland St. John's, Newfoundland A1B 3X9
1987
Canadian Technical Report of Fisheries and Aquatic Sciences No. 1566
Fisheries Pec hes I * and Oceans et Oceans
Fisheries and Marine Service
Technical Reports
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i
Canadian Technical Report of
Fisheries and Aquatic Sciences 1566
1987
SEA AGE AT MATURITY FOR ATLANTIC SALMON, SALMO SALAR,
IN NORTH AMERICA
by
R. A. Myers
Science Branch
Department of Fisheries and Oceans
P.O. Box 5667
St. John's, Newfoundland A1C 5X1
and
J. A. Hutchings
Department of Biology
Memorial University of Newfoundland
St. John's, Newfoundland AlB 3X9
ii
(c)Minister of Supply and Services Canada 1987
Cat. No. Fs 97-6/1566E ISSN 0706-6457
Correct citation for this publication:
Myers, R. A., and J. A. Hutchings. 1987. Sea age at maturity for Atlantic salmon, Salmo salar, in North America. Can. Tech. Rep. Fish. Aquat. Sci. 1566: iv + 18 p.
iii
CONTENTS
Abstract/Resume .......................................................... Introduction ................................................ Positive Correlation Between Growth Rate and Age at Maturation
Spawning marks misinterpreted as annuli A non-robust measure of growth rate Total length used instead of fork length
...................... ~ ..... for one ri ver
1. 2. 3. 4. 5.
Data inconsistencies Exclusion of populations not having 3SY salmon . .......... .
Discussion ............................................................... Acknowledgments
References ...............................................................
iv
1
1
1 2 3 3 3
3
4
4
iv
ABSTRACT
Myers, R. A., and J. A. Hutchings. 1987. Sea age at maturity for Atlantic salmon, Salmo salar, in North America. Can. Tech. Rep. Fish. Aquat. Sci. 1566: iv + 18 p.
We provide background documentation for "A spurious correlation of an inter-population comparison of Atlantic salmon life histories" (MYers and Hutchings 1987), in which Schaffer and Elson's (1975) conclusions regarding the evolution of age at maturity in Atlantic salmon, Salmo salar, are reexamined. We could not sUbstantiate their positive correlation of sea age at maturity with growth at sea and concluded that their results had been based upon statistical artifacts and an erroneous data set. This report collates the unpublished data used by Myers and Hutchings (1987), provides photographic evidence of incorrectly aged scales, and summarizes the errors in Schaffer and Elson's (1975) original analysis and data set.
~ ~
RESUME
Myers, R. A., and J. A. Hutchings. 1987. Sea age at maturity for Atlantic salmon, Salmo salar, in North America. Can. Tech. Rep. Fish. Aquat. Sci. 1566: iv + 18 p.
Les auteurs presentent des donnees documentaires pour 1 'etude intitulee "A spurious correlation of an inter-population comparison of Atlantic life histories" (Myers et Hutchings 1987). Cette etude est une evaluation critique des conclusions formulees par Schaffer et Elson (1975) sur l'age atteint a la maturite dans le cas du saumon de 1 'Atlantique (Salmo salar). Elle n'etaye pas la correlation positive relevee par ces chercheurs entre "age atteint en mer a la maturite et la croissance en milieu marin. Myers et Hutchings formulent la conclusion que les resultats obtenus etaient bases sur des erreurs statistiques et une serie de donnees erronees. Le present rapport rassemble les donnees inedites utilisees par Myers et Hutchings (1987), contient des photographies d'ecailles dont 1 'age a ete incorrectement etabli et resume les erreurs de 1 'analyse et de la serie de donnees de Schaffer et Elson.
1
INTRODUCTION
Schaffer and Elson (1975) tested the applicability of life history theory to explain the variation in sea age at maturation among North American populations of Atlantic salmon, Salmo salar. They concluded that (1) mean age of first spawning was positively correlated with marine growth rate after the grilse stage, (2) that the within-population variation in age at maturation increased and then decreased with increasing latitude, and (3) that sea age at maturation was positively correlated with river length.
Myers and Hutchings (1987) reexamined the analysis and data upon which Schaffer and Elson (1975) based the first two conclusions indicated above. In addition, Myers and Hutchings (1987) analyzed a more extensive data set and found sea age at maturation to be independent of growth rate at sea in Atlantic salmon. Furthermore, there was no evidence of a latitudinal trend in the variability about mean age at maturation. Schaffer and Elson's (1975) results were attributed to the application of non-robust statistical procedures for estimating growth rate and variation in age at maturity, and to the use of an erroneous data base.
The objectives of this report are (1) to collate the unpublished data used in .our aforementioned analyses (Myers and Hutchings 1987), (2) to provide photographic examples of scales which had been incorrectly aged, and (3) to summarize the errors in the analysis and data used by Schaffer and Elson (1975).
Unpublished data are presented as length-frequency histograms in Fig. 1.
POSITIVE CORRELATION BETWEEN GROWTH RATE AND AGE AT MATURATION
Schaffer and Elson's (1975) conclusion that growth rate at sea is positively correlated with sea age at maturation is invalid for five reasons.
1. SPAWNING MARKS MISINTERPRETED AS ANNULI
Newfoundland records were the most complete of all data sets available (Table 1). Consequently they were examined in their entirety prior to inspection of data from other regions. Scales were re-examined for those individuals having lengths over two standard deviations from the population mean. Ageing errors in the Newfoundland data were primarily (over 70%) of one kind. Spawning marks were interpreted as annuli. Thus salmon that had previously spawned were misclassified as virgin fish of an older sea age class. Given that previous spawners grow less in the year of their second spawning than virgin fish (Allen et ale 1972), these ageing errors resulted in a systematic underestimation of the mean lengths at age for multi-sea-year salmon.
Ageing errors can be attributed to the misinterpretation of spawning marks as annuli. Spawning marks result from the erosion that occurs at the outer scale margin during the maturation/reproduction process. The erosion is likely a consequence of calcium deficiency since Atlantic salmon do not feed during the freshwater phase of their spawning migrations (Jones 1959).
2
The spawning marks indicated in Fig. 2a-2d were interpreted as annuli in the original age determinations of Exploits and Sand Hill salmon. The overall effect of such misclassifications is a significant underestimation of growth rate (note the fork lengths of the misclassified fish). Virgin 2SY salmon from both populations are presented in Fig. 2e-2f for comparison.
The data set used by Schaffer and Elson (1975) for the Exploits River salmon population included several misclassified individuals. Salmon had been incorrectly classified into all three sea age classes. Inclusion of misclassified fish reduces the length difference between 2SY and 1SY salmon from 23.6 cm to 14.0 cm, resulting in a significant underestimation of growth.
The following are rates of misclassification for the two rivers which had complete scale collections:
Number Number misclassified Number correctly
misclassified classified Number grilse originally aged Exploits River
2SY salmon 8 10 0.7% 3SY salmon 2 0 0.2%
Sand Hill River 2SY salmon 3 389 0.09% 3SY salmon 2 0 0.06%
In the Exploits River 1200 grilse were originally aged and in the Sand Hill River 3196 grilse were originally aged. Error rates of this magnitude were primarily responsible for Schaffer and Elson's (1975) positive correlation between age at maturation and marine growth (Myers and Hutchings 1987).
Five of the 14 populations included in Schaffer and Elson's (1975:Fig. 5) positive relationship between sea growth rate and age at maturity were comprised largely of one-sea-year (lSY) salmon. These populations were from the Exploits, Sand Hill, Big Salmon, and West rivers, and Little Rattling Brook (which is actually a tributary of the Exploits River). We have already noted the unreliability of the Sand Hill and Exploits data. The scales of the Little Rattling Brook and West River salmon have unfortunately been lost. These data were thus eliminated from our analyses. The length-at-age data for West River salmon were highly suspect as indicated by the mean lengths of 65.2 cm (n = 19) and 73.7 cm (n = 1) for fish classified as 2SY and 3SY salmon respectively. Jessop (1985) reanalyzed the data for t~~ Big Salmon River and discovered numerous age misclassifications. Ageing errors may be attributable to the fact that several of the rivers (e.g. Little Rattling Brook, Exploits, West) were not originally surveyed for research purposes per se, but rather to assess the feasibility of various enhancement projects. Consequently accuracy in ageing was not a priority.
3
2. A NONROBUST MEASURE OF GROWTH RATE
Growth in length during the first three years at sea decreases with age (Allen et ale 1972), hence the unweighted linear regression of mean size on virgin sea age employed by Schaffer and Elson (1975) was inappropriate. Instead, growth rates are more appropriately calculated as the difference between mean fork length of virgin 2SY and 1SY fish. Ageing errors were amplified by Schaffer and Elson's (1975) use of an unweighted regression. For example, in their analysis of the Sand Hill River data, the weight given to over 1700 1SY fish was equal to that attributed to four fish classified as 3SY salmon. Similarly, 955 1SY salmon were weighted equally with two 3SY fish from the Exploits River. Scale analyses revealed 3SY fish from both the Sand Hill and Exploits rivers to be previous spawners, not virgin 3SY salmon.
3. TOTAL LENGTH USED INSTEAD OF FORK LENGTH FOR ONE RIVER
Schaffer and Elson (1975) mistook total length for fork length in the data set of at least one river, the Narraguagus (Meister and Cutting 1967). This had the effect of overestimating the growth rate for this population. Correction of this mistake has a deleterious effect on their proposed relationship.
4. DATA INCONSISTENCIES
One data source used by Schaffer and Elson (1975) for Quebec populations appears to be misleading. Schiefer (1971) presented salmon age-length relationships on 11 rivers from the north shore of the Gulf of St. Lawrence. Several of these data sets show the mean length of 1SY salmon to be substantially lower (e.g. Moisie - 49 cm (n = 31); Mingan - 49 cm (n = 10); Ste. Marguerite - 49 cm (n = 12); Mistassini - 46 em (n = 4)) than means based upon much larger sample sizes from data provided by the Ministere du Loisir, de la Chasse et de la Peche, Quebec (Myers and Hutchings 1987:Table 1). Furthermore, the standard errors in length at age reported by Schiefer were not calculated correctly, i.e. they were at least an order of magnitude lower than is possible for length at age data. Thus, the variability in length at age could not be assessed. Since Schiefer's (1971) raw data were not available for reanalysis, they were excluded from Table 1. A recent analysis of these populations (Bielak 1984) sUbstantiated this discrepancy.
5. EXCLUSION OF POPULATIONS NOT HAVING 3SY SALMON
Populations in which 3SY salmon do not occur were excluded from Schaffer and Elson's (1975:Table 4) analysis of the age at maturity - marine growth rate relationship. Inclusion of these data greatly reduce the r2 of their correlation (see Myers and Hutchings 1987).
4
DISCUSSION
This report emphasizes the need for careful inspection of data sets, including a thorough examination of outliers, before they are used in any formal analysis. Ageing errors of the type we describe can be relatively common in salmonid age determinations. The use of erroneous data can produce spurious correlations, such as those identified herein (Schaffer and Elson 1975), thus rendering the validity of any conclusions drawn from such results either questionable or invalid (Myers and Hutchings 1987).
ACKNOWLEDGMENTS
Data from New Brunswick were provided by M. Chadwick, B. Jessop, and B. Randall; from Nova Scotia by L. Marshall and R. Semple; and from Newfoundland by E. Ash, B. Dempson, J. Gibson, H. Lear, M. O·Connell, R. Porter, J. Pratt, and D. Reddin. (All of the above are employees of the Canadian Department of Fisheries and Oceans.) Data for Quebec were provided by Y. Cote and G. Ouellet, Ministere du Loisir, de la Chasse et de la Peche, Gouvernement du Quebec. Scale age determinations were checked by D. Reddin and B. Short, Department of Fisheries and Oceans, St. John·s. R. Ficken prepared the scale photographs.
REFERENCES
Allen, K. R., R. L. Saunders, and P. F. Elson. 1972. Marine growth of Atlantic salmon, Salmo salar, in the northwest Atlantic. J. Fish. Res. Board Can. 29: 1373-1380.
Bielak, A. T. 1984. Quebec north shore Atlantic salmon stocks. Ph.D. thesis, Univ. Waterloo, Waterloo, Ontario.
Jessop, B. M. 1985. Analysis of the run of Atlantic salmon (Salmo salar) to the Big Salmon River, New Brunswick. Can. Tech. Rep. Fish. Aquat. Sci.
Jones, J. W. 1959. The salmon. Collins, London. 192 p.
Meister, A. L., and R. E. Cutting. 1967. A preliminary report of the composition of the spaw·ning runs of Atlantic salmon, Salmo salar, in Maine rivers for the period 1962-66. Int. Comm. Northwest At'. Fish. Redb. Part III: 53-57.
Myers, R~ A., and J. A. Hutchings. 1987. A spurious correlation in an inter-population comparison of Atlantic salmon life histories. Ecology 68: 1839-1843.
Schaffer, W. M., and P. F. Elson. 1975. The adaptive significance of variations in life history among local populations of Atlantic salmon in North America. Ecology 56: 577-590.
5
Schiefer, K. 1971. Ecology of Atlantic salmon, with special reference to occurrence and abundance of grilse, in North Shore Gulf of St. Lawrence Rivers. Ph.D. Thesis, Univ. Waterloo, Waterloo, Ontario. 129 p.
Table 1. Relationship between length and number of years spent at sea for virgin Atlantic salmon in North America.
Latitude Fork length in cm (sam~le size) Coll ection River ( 0) ISY 2SY 3SY method l Year Reference
Newfoundland:
Exploits 49.0 52.0 (846) 75.6 (10) F 63 Myers and Hutchings(1987) Hunt 55.0 57.8 (8) 76.6 (24) A 80 .. North Harbour 47.0 55.1 (38) 76.3 ( 11) F 70, 71, 73, 74 Lear and Day (1977) Pinware 52 • ..1 53.2 (748) 74.3 (142) A 80, 81 Myers and Hutchings(1987) Sandhi 11 54.0 53.9 (3196) 73.0 (389) 98.1 (2) A 67, 69-74 Eagle 54.0 54.4 (302) 74.7 (9) A 71, 79 Forteau 51.5 54.2 (353) 72.9 (11 ) A 79-81 Highlands 48.0 53.3 (16) 73.4 (4) F 82 Humber 49.0 55.0 (297) 73.5 (9) 86.5 (17) F 67, 76, 79-81 Little Codroy 47.5 54.1 (197) 75.1 (163) 89.6 (35) F 57-63 Lomond 49.5 51.4 (108) 70.7 (7) A 75, 78-81
New Brunswick:
Miramichi 47.0 52.1 (8604) 72.8 (4016) 82.4 (48) F 71-83 3 Saint John 46.5 56.3 (583) 78.0 (474) F 77-79 Myers and Hutchings(1987) Big Salmon 45.0 53.2 (1654) 70.8 (139) F 65-73 Jessop (1986) Restigouche 48.0 53.2 (1488) 76.4 (701) 92.6 (335) F 72-80 Randall (1984)
Nova Scotia:
LaHave 44.0 53.8 (68) 72.5 (28) F 82 Myers and Hutchings(1987) Liscomb 45.0 52.3 (770) 72.4 (82) 91.7 (5) F 79-82 .. Margaree 46.0 53.5 (17) 71.1 (23) 81.7 (5) F 73 II
North 46.0 54.6 (2) 72.3 (35) F 72 II
Phil i P 44.5 56.6 (22) 74.4 ( 167) 86.7 (34) A 78 II
St. Mary's 44.0 54.0 (60) 74.9 (20) 91.1 (9) A 74 II
Table 1 (cont'd)
Latitude Fork length in cm (samele size) Collection River (0 ) ISY 2SY 3SY method l Year Reference
Quebec:
Bouleau 50.0 50.6 (15) 74.6 (20) G 72, 73 Randall and Power (1979) Pigou 50.0 53.1 (5) 72.7 (7) G 72, 73 Randall and Power (1979) Cap-Chat 49.0 56.3 (16) 78.9 (73) 93.4 (36) A 74, 75, 77 Myers and Hutchi ngs (1987) Corneille 50.0 53.3 (203) 70.0 (369) A 64-68 II
Grande 48.0 54.9 (12) 74.4 (76) 90.9 (9) A 83 II
Koksoak 57.0 61. 7 (221) 78.6 (253) G 80 Robitaille et ale (1984) Leaf 58.5 62.4 (6) 79.7 (44) G 68 Lee and Power (1976) Madeleine 49.0 51.5 (172) 75.2 (334) 92.1 (53) A 72, 75-79 Myers and Hutchings (1987) Matamek 50.0 52.9 (20) 72.9 (6) G 74 II
Matane 49.0 54.8 (186) 71.9 (149) 90.3 (56) A 69 II
Matapedia 48.0 56.8 (66) 80.0 (354) 94.6 (171) A 73 II
Nabisipi 50.0 54.5 (61) 77.4 (1252) 87.6 (14) G 60-62, 63, 65-67 II
Pt. Saguenay 48.0 56.7 (182) 79.1 (39) 92.3 (83) A 78, 79 Myers and Hutchings (1987) Ste. Anne 49.0 56.1 (19) 80.8 (107) 95.8 (39) A 73, 74 II
Ste. Ma rgueri te 48.0 52.8 (63) 75.2 (70) 90.1 (75) A 69, 76 II
St. Jean 50.0 53.0 (35) 75.9 (73) 89.3 (3) A 77 II
St. Jean (Gaspesie) 48.5 54.4 (60) 73.3 (157) 90.7 ( 11) F 78-79, 83 II
Trinite 49.0 54.2 (319) 74.7 (21) A 81 II
Watshishou 50.0 53.3 (189) 70.4 (254) A 81-83 RileY,etal. (1984)
Maine:
Narraguagus2 44.5 54.8 (13) 69.8 (964) 81.7 (19) F 62-66 Meister and Cutting (1967)
IF = Counting fence; A = Recreational angling; G = Research gill nets within river/estuary. 2Lengths given in Schaffer and Elson (1975) are total, not fork length. 3R. G. Randall, Canadian Department of Fisheries and Oceans, Moncton, New Brunswick.
SANDHILL HUNT
FREQUENCY
I •••
FREQUENCY
8e.
6ee
48.
288
8
FREQUENCV
128
lee-
8.
68 ~ i , ,
I 4 4 4 5 5 5 5 5 6 666 6 7 7 7 7 7 B B 8 8 8 9 9 999 • 4 6 8 • 2 4 6 8 8 2 4 6 8 8 2 4 6 8 8 2 4 6 8 • 2 4 6 8 •
LEItGTH "I DPO I NT
EAGLE
J
2
• ~ ____ ~LULL ______ -LUU~UU~-----------I
4 4 4 5 555 5 6 6 6 6 6 1 177 788 8 8 8 8 9 9 9 9 • 4 6 8 • 2 4 6 8 • 2 4 6 8 • 2 4 6 8 • 2 4 6 8 • 2 4 6 8 •
LENGTH "IDPOIItT
PIItUARE
FREQUENCY
I 4 4 455 5 5 5 6 6 666 7 7 7 7 7 8 8 8 8 8 9 9 9 9 9 • 4 6 8 • 2 4 6 8 8 2 4 68. 2 4 6 8 • 2 4 6 8 • 2 4 6 8 •
LENGTH "IDPOIItT
fig. 1. length/age-frequency histograms for selected North American Atlantic salmon populations. Grilse (ISY salmon) are denoted by empty histograms, 2SY salmon are denoted by cross-hatched histograms, and 3SY salmon are denoted by solid histograms.
158
5 •
• I 4 4 455 5 5 5 6 6 6 6 6 7 7 7 7 7 8 888 8 9 8 8 9 9 • 4 6 8 • 2 4 6 8 • 2 4 6 8 • 2 4 6 8 • 2 468 • 2 468 •
LEItGTH "I DPO I itT
00
FREQU£ttCY
38
28
18
4 4 4 5 5 5 5 5 6 6 6 667 7 7 7 7 B B B B B 9 999 9 ~ 4 6 8 8 2 4 6 8 8 2 4 6 B 8 2 4 6 B 8 2 4 6 B • 2 4 688
LEHGTH IIIDPOIHT
SAINT JOHN
FREQUEHCY
288
158
188
58
4 4 4 5 5 555 666 6 6 7 7 7 7 7 8 8 8 B B 999 9 9 ~ 4 6 B • 2 4 6 B • 2 4 6 B 8 2 4 6 B • 2 4 6 8 • 2 4 6 8 8
LEHGTH IIIDPOIHT
FREQUENCY
1 ..
88
68
48
28
FORTEAU
1 4 4 4 5 5 5 5 5 6 6 6 6 6 7 7 777 B 8 8 8 B 9 999 9 • 468 • 2 4 6 B 8 2 4 6 B 8 2 4 6 B 824 6 8 8 2 4 6 B 8
LEHGTH IIIDPOIHT
FREQUENCY
128
188
88
68
48
28
1 4 4 4 555 5 566 6 6 6 7 7 7 7 7 B B B 8 B 9 9 9 9 9 8 4 6 8 8 2 4 6 B 8 2 4 6 8 8 2 4 6 B 8 2 4 6 B 8 2 4 6 8 8
LEHGTH IIIDPOIHT
I'IARGAREE
FREQUENCY
5
3
2
1 ~ ~ ~ 5 5 5 5 5 6 6 6 6 7 7 7 7 7 8 8 8 8 8 9 9 9 9 9 e ~ 6 8 9 2 ~ 6 882 ~ 6 8 e 2 4 6 8 8 2 ~ 6 8 e 2 ~ 6 8 9
LENGTH I'IIDPOINT
ST. MAR~
FREQUENCY
29
15
18
5
1 4 4 ~ 5 555 5 6 6 6 6 6 7 7 7 7 7 8 8 8 8 8 9 9 9 9 9 8 4 6 8 8 2 ~ 6 8 8 2 ~ 6 8 8 2 ~ 6 8 8 2 4 6 882 ~ 6 8 e
LENGTH PlIDPOINT
CAP-CHAT
FREQUENCY
25
28
15
18
5
1 ~ ~ ~ 5 5 5 5 5 6 6 6 6 677 7 7 7 8 888 8 9 9 9 9 9 e ~ 6 8 8 2 ~ 6 8 e 2 ~ 6 8 • 2 ~ 6 8 8 2 4 6 8 8 2 ~ 6 8 8
LENGTH IIIDPOINT
CORNEILLE
FREQUENCY
188
88
68
~8
I 4 ~ ~ 5 5 5 5 5 6 6 6 6 6 7 777 7 8 8 8 8 8 9 9 9 9 9 • ~ 6 8 • 2 ~ 6 8 • 2 4 6 8 • 2 ~ 6 8 9 2 ~ 6 8 8 2 4 6 8 8
LENGTH IIIDPOINT
...... o
GRAHDE
FREQUENCY
28
IS
18
5
4 4 4 5 5 5 5 5 6 6 6 6 6 7 7 7 7 7 8 8 8 8 8 9 9 9 9 9 ~ 4 6 882 4 6 8 • 2 4 68. 2 4 6 882 468 8 2 4 6 8 8
FREQUEHCY
188
LENGTH PlIDPOIHT
PlADElEIHE
4 4 4 5 5 5 5 5 666 6 6 7 7 777 888 8 8 9 9 9 9 9 , 4 6 882 4 6 8 • 2 4 6 8 8 2 4 6 8 • 2 4 6 8 • 2 4 688
LEHGTH PlIDPOINT
PlATAIIEK
FREQUENCY
7
6
5
4
3
2
8 lun
" 4 4 4 5 5 5 5 566 6 6 6 7 7 7 778 8 8 8 8 9 9 9 9 9 , 46882 4 6 8 8 2 4 6 8 • 2 4 6 8 8 2 4 6 8 8 2 468 8
LENGTH PlIDPOINT
PlATANE
FREQUENCY
68 1 58
48
38
28
18
4 4 4 5 5 5 5 5 6 6 6 6 6 7 777 7 8 8 8 8 8 9 9 9 9 9 ~ 4 6 8 • 2 4 6 8 • 2 4 6 882 4 6 8 • 2 4 6 8 • 2 4 68.
LENGTH PlIDPOINT
FREQUENCY
tee 1 a0 1
j
68 j
1 1
~8 1 1
a8
I'IATAPfDIA
1 4 ~ ~ 5 5 5 5 5 666 6 6 7 7 7 7 7 8 8 8 8 8 9 9 9 9 9 8 ~ 6 8 8 a 4 6 8 8 a 4 6 8 8 a 4 6 8 • a ~ 6 8 8 a 4 6 8 0
LENGTH PlIDPOINT
NABISIPI
FREQUENCY
~88
388
aee
188
1 ~ 4 5 555 5 666 6 6 7 7 7 7 7 8 8 8 8 8 9 9 999 8 680 a ~ 6 8 • a ~ 6 8 • a 4 6 8 • a ~ 6 8 • a ~ 6 8 8
LENGTH I'IIDPOINT
PTE. SAGUENAY
FREQUENCY
58
48
38
a0
10
8 ~L-~LD~UL~~L-~-L~LULD~U---~L-----l
~ 4 ~ 5 5 5 5 566 6 6 6 7 7 7 7 7 8 8 8 8 8 9 9 9 9 9 • 4 6 8 • a ~ 6 8 • a ~ 6 8 8 a 4 6 8 • a 4 6 8 8 a ~ 688
LENGTH I'll DPOINT
STE. ANNE
FREQUENCY
38
a0
18
1 ~ 4 4 5 555 5 6 6 666 777 7 7 8 8 8 8 B 9 9 9 99. 4 6 8 • a 4 6 8 • a 4 6 B • a 4 6 8 • a ~ 6 B • a 4 6 B •
LENG TH 1'1 I DPO I NT
...... N
5TE. I'IARGUER ITE
FREGUEHCY
25
~ ~ ~ 5 555 5 666 6 6 1 1 1 1 1 8 8 8 8 8 9 9 9 9 9 ~ ~ 6 8 8 2 4 6 8 8 2 ~ 6 8 8 2 ~ 6 8 8 2 ~ 6 8 8 2 ~ 6 8 8
lEHGTH I'IIDPOIHT
ST. JEAH
FREQUEHCY
38
28
18
I ~ ~ ~ 5 5 5 5 5 6 6 6 6 6 1 1 1 118 8 8 8 8 9 g 9 9 9 8 ~ 6 882 ~ 6 8 8 2 ~ 6 8 • 2 ~ 6 882 ~ 6 882 ~ 688
lEHGTH I'IIDPOIHT
5T. JEAII (GA5pf)
FREQUEHCY
~8
38
28
18
~ ~ ~ 5 5 5 5 5 6 6 666 1 1 1 1 1 8 8 8 8 8 9 9 9 9 9 ~ ~ 6 8 8 2 ~ 6 8 8 2 ~ 688 2 ~ 6 882 4 6 8 • 2 ~ 6 8 8
lEHGTH IIIDPOIHT
TRIHITf
FREQUEHCY
188
88
68
~8
28
~ ~ ~ 5 5 5 5 5 6 6 6 6 6 1 1 1 1 1 8 8 8 8 8 9 999 9 ~ ~ 688 2 ~ 6 8 8 2 ~ 6 8 8 2 ~ 688 2 ~ 6 8 8 2 ~ 688
lEHGTH 1'1 I DPO IHT
...... eN
14
\ • . .
, ,..~ ....... : • .t
'" 6 0.'·. . .~. -. ,"' . . - ~.~ .. , .
. -. . . I·
. ,
. '. \, .
. ./
- , A'
.'
Fig. 2a. Scale photograph of a previously spawned salmon from the Sand Hill River that had originally matured as a 1SY fish; misclassified as a virgin 2SY salmon. (Specimen no. 58; caught 20 July 1970; FL = 59.0 cm.)
• .. f. . ., :. .. , ...
l ... : '. .... fa-·
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, .. •
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Fig. 2b. Scale photograph of a previously spawned salmon from the Exploits River that had originally matured as a virgin ISY fish; misclassified as a virgin 2SY salmon. (Specimen no. 636; caught 30 July 1963; FL = 57.0 cm.)
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Fig. 2c. Scale photograph of a salmon from the Sand Hill River that had previously spawned on two occasions following original maturationls a 1SY fish; misclassified as a virgin 3SY salmon. (Specimen no. 71; caught 10 July 1971; FL = 76.7 cm).
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Fig. 2d. Scale photograph of a virgin 2SY salmon from the Sand Hill River (Specimen no. 5; caught 9 July 1972; FL = 73.5 em.)
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Fig. Zo. Scale photograph of a virgin 2SY salmon from the Exploits River. (Specimen no. 87; caught 15 July 1963; FL = 81.0 em.)
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