Graduate Thesis Or Dissertation
 

Growth and reproduction of the lanternfish Stenobrachius leucopsarus

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/3197xp37h

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  • 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 after spawning. Comparison with previously unpublished information from collections made in Monterey Bay, California, indicates that spawning may occur earlier there than off Oregon, but growth rates and sizes in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.
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