Newly-hatched
pike fry live on their yolk sacs for several weeks but they need to capture invertebrate
food when they are 10-12mm long. By the time they have grown to 5-6cm long, pike
tend to switch to a diet of fish. This explains why pike usually spawn sometime
before their prey: the young pike have grown large enough to eat other species
of fish just as they hatch!
The dietary
requirements of pike are also and, in general terms, a diet comprising between
13oz and 1.5lb of prey fish per pound of pike per annum is needed to merely keep
the pike alive (their 'maintenance ration'). Where pike are undergoing normal
growth 2.5-3.5lb of prey fish per pound of pike per annum is a common ration which
ensures such normal growth.
Conversion
from prey flesh to pike flesh can also be predicted, and the ratio between weight
gain and total food consumed during normal growth is often between 1:5 and 1:10.
Prey
choice seems to be governed entirely by its availability to pike. However, there
is some evidence that pike may select soft-rayed species in preference to fish
bearing spines. Although there are reports that spined fish (usually perch or
related species) are the dominant prey of pike. For example on one water analyses
of the stomach contents of large pike revealed substantial numbers of perch and
relatively few trout. That pike tend to be opportunist, rather than selective,
predators is supported by the fact that the stomach contents listed by several
workers comprised nearly the entire range of fish species present at the studied
sites.
For example where perch and
char are present the pike tend to feed on perch for most of the year, but char
figure highly in the pike's diet during the autumn. The explanation is that the
char move from their usual deep-water habitat and shoal in shallow, marginal areas
in readiness for spawning at this time of year!
The
scientific literature does not support the notion that pike will always 'prefer'
a particular prey species irrespective of its abundance. This undermines the theory
that pike will actually select salmon or trout in game fisheries; pike tend to
eat whatever they can catch most easily.
Photo
courtesy of Dave Lumb
NEWS