Table 1 Some physiological and related differences between young and older WBE.

Here, item (1) is the cause of all others. “Relative” stands for “per unit weight.”

No.Young/small WBEOlder/larger WBESource(s)
1Relative gill surface area is high.Relative gill surface area is low.See text
2Thus, relative O2 supply is high.Thus, relative O2 supply is low.See text
3Growth in weight is accelerating.Growth in weight is decelerating.See Figs. 1 and 3
4High temperatures and thus
shallower habitats are preferred.
Low temperatures and thus deeper
habitats are preferred.
(38, 140)
In Cyprinodon macularius, a
temperature of 30°C is “optimal
only up to an age of 22-28 weeks.”
In older C. macularius, “the
temperature optimum shifts
gradually to 22-26°C.”
(92); see text for other species
5Relative food consumption is
Relative food consumption is low.(141)
6Food conversion efficiency is high.Food conversion efficiency is low,
trending toward zero.
(108, 109, 142)
7Young adult fish may skip spawning,
but spawn during the next season.
Adults do not skip spawning; large
adults may spawn repeatedly in a
spawning season.
(16, 143145)
8Enzymes in tissues are mainly
Enzymes in tissues are mainly glycolytic.(53); also see text
9Fish otoliths contain proteinaceous
The external layers of fish otoliths are
purely crystalline.
(146, 147)
10Clear daily “rings” are formed in
otoliths of fish and statoliths of
Daily “rings” in otoliths or statoliths
are blurred and, later, disappear
(16, 148, 150)
11Extensive seasonal migrations are
not undertaken.
Extensive, often temperature-driven
seasonal migrations are
12Fat content is low.In fish, fat content is high, particularly
when seasonal temperature
oscillations are high.
(16, 97)