Table 6 Arguments raised against the GOLT: Spawning versus growth and vice versa.

NoArgumentsRefutations
6.1Old/large adult fish stop growing because all their
energy goes to reproduction (7077)
Well-fed, non-reproducing fish (e.g., in aquaria)
stop growing at some point. In addition, the
females of >80% of fish species grow to be
larger than the males (see www.fishbase.org
and section on “Fish growth vs. reproduction”).
6.2“Pauly’s assumption that female fish have higher
reproductive output than male fish is
unsupported by data. There is no pattern of
female fish investing more in reproduction than
males in fish (or other water-breathing
ectotherm Parker et al. (85). Indeed, for the
species given by Pauly (84), females invest
relatively less in reproduction than males as a
proportion of body mass (see figure 5.5 in
Sarre’s doctoral dissertation (173)” (83). Note
that “figure 5.5” is a plot of ova stages versus
body weight in female (only) black bream
(Acanthopagrus butcheri), which does not deal
with the female-to-male comparison at hand; it
is likely that the authors meant figure 5.6, which
compare the gonosomatic index (GSI) of
females and male black breams. In addition, in a
context similar to that above, an author (174)
proposed the ad hoc hypothesis that the
greater reproductive investment of the female
is more apparent than real, i.e., “[t]he male
gonad often weighs less than the female
gonad. This does not mean smaller spawning
loss in males because sperm, consisting almost
entirely of DNA, RNA and lipoids, is likely to be
the most expensive substance in the fish body.”
A review of 168 mammal, 97 bird, 3 reptile, 100
amphibian, 98 fish, and 16 invertebrate species
(175) concluded that, overall, the cost of
reproduction, in female was up to three orders
of magnitude higher than for males. This
confirms Gould (176), who wrote “[s]perm is
small and cheap, easily manufactured in large
quantities by little creatures. A sperm cell is
little more than a nucleus of naked DNA with a
delivery system. Eggs, on the other hand, must
be large, for they provide the cytoplasm (all the
rest of the cell) with mitochondria […]), and all
other parts that a zygote needs to begin the
process of embryonic growth….” Parker et al.
(85) state in their abstract, that sessile
invertebrates (not “fish”) are “subject mainly to
selection on gamete production and gamete
success and so high gonad expenditure is
expected in both sexes. […]When GSI is
asymmetric, female GSI usually exceeds male
GSI, as least in echinoderms. […] Intriguingly,
higher male GSI also occur in some species […]
of gastropod molluscs”. If these authors had
found that male GSI routinely matches that of
females, they would not have used the word
‘intriguingly’. They also note that their “limited
data also suggest that higher male GSI may be
the prevalent pattern in sperm casters (where
only males release gametes).” As for figure 5.6 in
Sarre’s unpublished thesis, it shows male GSI to
be occasionally higher than female GSI, but GSI
is an index relating gonad weight a given time
to the weight of the body, not the rate of
production of gonad tissue, which alone relates
to reproductive costs.
6.3A critique (166) of (7) included “the bioenergetic
model assumes that the term scaling directly
with weight is due to catabolism, but the there
is a strong case that reproductive investment is
the principal factor (75, 177, 178).”
The answer to this (7) was that “Brander et al.
argue that fish growth is inversely proportional
to reproductive investment. However, this […]
cannot explain why female fish (which have a
much larger reproductive investment than
male fish) reach larger sizes than male in the
majority of fish species, and why sterile fish […]
grow asymptotically. Moreover […] diploid
(reproductively active) and triploid (sterile) fish
show very similar growth patterns despite large
differences in reproductive investment (80).”