Growth and spatiotemporal distribution of juvenile shortfin mako (Isurus oxyrinchus) in the western and central North Pacific

Abstract

This paper presents an estimation of growth curves and spatiotemporal distributions of juvenile shortfin mako shark (Isurus oxyrinchus) in the western and central North Pacific Ocean using port sampling data collected from 2005 to 2013. The monthly length compositions show a clear transition of three modes in the size range of smaller than 150-cm precaudal length (PCL), which were believed to represent the growth of age-0 to age-2 classes, and they were then decomposed into age groups by fitting a Gaussian mixture distribution. Simulation data of lengths at monthly ages were generated from the mean and standard deviation of each distribution, and fit with a von Bertalanffy growth function. Parameters of the estimated growth curves for males and females were 274.4 and 239.4 cm PCL for the asymptotic length and 0.19 and 0.25 year À1 for the growth coefficient indicating apparently faster growth than previously reported. Generalised linear models were applied to age-0 to explore the seasonal changes of PCL by area. They were born during late autumn and winter off the coast of north-eastern Japan, an area known to have relatively high productivity compared with other pelagic areas, and gradually expanded their habitat eastward and northward with the seasons as they grew. Journal compilation Ó CSIRO 2015 www.publish.csiro.au/journals/mfr B Marine and Freshwater Research M. Kai et al.

Size, Age, and Spatial–Temporal Distribution of Shortfin Mako in the Mexican Pacific Ocean

“…The migration of age-0 and 1-year-old juveniles observed in our results could be related to the increase in SST during the year, which coincides with the findings reported by Kai et al (2015) in the North Pacific Ocean and western Pacific Ocean for the Shortfin Mako and which is related to the thermal preferences of this species. Another possibility is that juveniles may be migrating in response to the movement of smaller fish that serve as food and in turn seek the nutrient-rich waters of coastal upwellings, such as the California Current.…”

Distribution, body length, and abundance of blue shark and shortfin mako offshore of northeastern Japan, as determined from observed pelagic longline data, 2000–2014

“…Comparison of the length frequencies from these surveys with the reported growth parameters of North Pacific blue shark (Nakano, ) and shortfin mako (Semba et al ., ; Wells et al ., ; Kai et al ., ) indicated that both species caught in the surveys ranged from the young‐of‐the‐year class to young adults. In particular, shortfin mako showed an apparent mode at a precaudal length of around 70 cm, which is close to its recruitment size (Semba et al ., ).…”

Oxytetracycline age validation of an adult shortfin mako shark Isurus oxyrinchus after 6 years at liberty

“…The age and growth of the shortfin mako Isurus oxyrinchus Rafinesque 1810 has been studied since the early 1980s (Cailliet & Bedford, ; Pratt & Casey, ; Francis & Duffy, ; Ardizzone et al , ; Bishop et al , ; Natanson et al , ; Cerna & Licandeo, ; Semba et al , ; Wells et al , ; Doño et al , ; Kai et al , ). Several methods have been used in past studies including length‐frequency analysis and tag‐recapture growth, but the most common method for age determination has been counting alternating growth bands in vertebral centra.…”