|Abstract or Summary
- Growth and reproductive patterns of the common lanternfish,
Stenobrachius leucopsarus, are described by length frequency
analysis, otolith analysis and examination of ovaries.
Length frequency analysis, employing the probability paper
method of analysis of polymodal distributions, of three and one-half
years of monthly midwater trawl collections off Oregon showed that
fish in the fourth year of growth and younger form distinct length
classes in collections. Growth is approximately linear during the
second, third, and part of the fourth year of life. The average rate
of growth during this time is 1.59mm (standard length) per month.
Fish on their first birthday average 23mm long, on their second
birthday 41mm long, and on their third birthday 59mm long.
Otolith analyses indicated that some fish live to be eight years
old, but confidence in this method is limited to fish five years old and younger. By fitting mean lengths of age groups defined by otolith
analyses with the von Bertalanffy equation, the asymptotic length
was estimated to be about 85mm, and the rate at which growth to
the asymptote decreases to be about 0.34.
Back calculation of lengths at the times of annulus formations
gave another set of estimated mean lengths of age groups. Fitting
the von Bertalanffy equation to these data described a growth curve
comparable to the one described by otolith analyses. Transforming
the growth curve to growth in weight by a length-weight relationship
indicated that the inflection in growth occurs at about age four years.
Spawning, determined from egg measurements, is thought to
occur from December to March. Reproductively mature individuals
are four years old and older. Recruitment of young size groups
was also seasonal, 20-25mm individuals appearing in largest numbers
in trawl samples in the winter, presumably about eight months
Comparison with previously unpublished information from
collections made in Monterey Bay, California, indicates that spawning
may occur earlier there than off Oregon, but growth rates and
sizes in age groups V and younger are very similar. Comparisons
with published results of otolith analyses show similar age determinations
for the younger age groups.