Late
summer and early fall usually signal the time for Louisiana’s
annual run of large redfish, or “bull reds” as
they are usually called. During this period, the offshore
schools of large redfish move nearer to the coast, especially
to areas near passes, for their annual spawn. Redfish spend
the first years of their lives in inshore estuaries, feeding
and growing rapidly. By 4 or 5 years of age, almost all of
them have left these waters and joined the offshore schools
of adult redfish.
Age and
growth research done in the late 1980s by LSU biologists on
redfish captured from offshore schools provides interesting
information. In this study, the biologists read the growth
rings in the otoliths (ear bones) of 1,690 redfish taken offshore
by purse seine, gill net and hook and line. The fish were
taken from waters between northeast Texas and western Ala-bama,
with most of the fish being captured off the Louisiana coast.
The fish ranged in size from 22 to 42 inches in length. The
oldest female was 36 years old (40 inches and 26.3 pounds)
and the oldest male was 37 years old (38 inches and 23.1 pounds).
Female
redfish were significantly larger than males, not because
they lived longer, but simply because they grew faster throughout
their lives in offshore waters. They found a few 2-year-old
redfish in their samples from offshore. At that age, females
averaged 27.6 inches and about 9 pounds. Males at that age
averaged 26.8 inches and a little over 8 pounds. The size
gap between the sexes remained fairly small until 9 years
old. At that age, females averaged 33.2 inches and 16.7 pounds
and males averaged 32.4 inches and 15.1 pounds. Then the gap
widened.
By age-15,
the growth rate for both sexes began to slow, but the growth
rate for males slowed even more than for females. At that
age, females averaged 36 inches and 22 pounds, and males averaged
34.4 inches and 18.7 pounds. By 30 years old, the average
size for females was calculated at 39 inches and 29.3 pounds.
Males averaged 35.6 inches and 22.2 pounds and their growth
rate had become extremely slow.
The biologists
noted that it was impossible to determine the age of a fish
by its size, be-cause the high variation in size of fish at
any age provides a great deal of overlap. For example, at
age 21, the largest fish was a female at 42.4 inches and 34
pounds and the smallest fish was a male at 31.2 inches and
15 pounds.
Download:
bullreds.pdf
(625KB)
