THE ARTIFICIAL PROPAQATION OF MARINE FISH
65
300
1
C
0
aJ
e
L
200
'c
.- 9
5
B loos
ul
0
L.
z
O L
manged in order of increasing population density (Fig. 20). The
disproportionately large number of small larvaa among denser populations is clearly seen. This is what one might expect from intra-specific
food competition, though the same pattern could be produced by
differentid mortality among slow-growing forms.
Survival or death, fast or slow growth, all reflect large differenoes
in individual adaptability to tank conditions. By this token, it is not
-
-
Survivors less than 20mm long
Survivors more than 20mm long
1
3
9
8
2
7
6
4
5
Number of tank
Fro. 20. Proportions of large end smdl pleice in tanks with differeno 8urvivor
densities : Port Erin, 1901. (After Shelboume. 1903b.)
at all certain that the larger survivors would necessarily be the best
sort of fish to liberate into the sea as part of an rsrtificial propagation
programme. On the other hand, if large size and " seaworthiness "
are related, then it would be efficient hatchery practice to eliminate
the retarded members of a mixed tank population aa early aa pomible
-virtually skimming the cream of the stock. Target production at a
low survival rate might then be met by boosting egg stocks.
B. The incidence of bitten$ns
Metamorphosed plaice larvae bite each other when crowded together in hatchery tanks, the damage being sustained on the marginal
65
300
1
C
0
aJ
e
L
200
'c
.- 9
5
B loos
ul
0
L.
z
O L
manged in order of increasing population density (Fig. 20). The
disproportionately large number of small larvaa among denser populations is clearly seen. This is what one might expect from intra-specific
food competition, though the same pattern could be produced by
differentid mortality among slow-growing forms.
Survival or death, fast or slow growth, all reflect large differenoes
in individual adaptability to tank conditions. By this token, it is not
-
-
Survivors less than 20mm long
Survivors more than 20mm long
1
3
9
8
2
7
6
4
5
Number of tank
Fro. 20. Proportions of large end smdl pleice in tanks with differeno 8urvivor
densities : Port Erin, 1901. (After Shelboume. 1903b.)
at all certain that the larger survivors would necessarily be the best
sort of fish to liberate into the sea as part of an rsrtificial propagation
programme. On the other hand, if large size and " seaworthiness "
are related, then it would be efficient hatchery practice to eliminate
the retarded members of a mixed tank population aa early aa pomible
-virtually skimming the cream of the stock. Target production at a
low survival rate might then be met by boosting egg stocks.
B. The incidence of bitten$ns
Metamorphosed plaice larvae bite each other when crowded together in hatchery tanks, the damage being sustained on the marginal