Title:Comparison between surface-reading and cross-section methods using sagittal otolith for age determination of the marbled sole Pseudopleuronectes yokohamae Authors:Jeong-Hoon LEE ABSTRACTTo find an appropriate method for age determination in the marbled solePseudopleuronectes yokohamae in Tokyo Bay, Japan, sagittal otoliths of 1343 individuals were observed by surface-reading and cross-section methods and the results were compared. Opaque zones occurred once a year and were regarded as annuli in both methods. The surface-reading method sometimes provided a lower count of the number of annuli than the cross-section method, and the frequency of this discrepancy was highest in older fish (males above 5 years, females above 4 years). The oldest female fish was estimated to be age 10 years by the cross-section method but 8 years by the surface-reading method. The cross-section method could provide a more accurate estimate of age and is therefore likely to be indispensable to estimations of longevity. In contrast, the surface-reading method is superior in terms of cost and time efficiency but is likely to underestimate the ages of older fish. However, growth equations based on age estimated by the surface-reading method were sufficiently accurate if males ≥ 5 years and females ≥ 4 years were combined as specific, single age groups of 5+ and 4+, respectively. KEY WORDSAge determination, Cross-section method, Growth, Otolith, Pseudopleuronectes yokohamae, Surface-reading method, Tokyo Bay 3 INTRODUCTIONThe marbled sole Pseudopleuronectes yokohamae distributed in Japan from southernHokkaido to Oita Prefecture in Kyushu, as well as in the Yellow Sea, the Bohai Sea, and the northern part of the East China Sea [1]. In Tokyo Bay, Japan, P. yokohamae is the dominant species in the megabenthic assemblage and is a highly valued fish species exploited by commercial fishers in the bay [2,3]. However, despite the importance of P.yokohamae as a commercial resource, the abundance of this species has markedly decreased since the late 1980s. According to statistics from the Shiba Branch of Yokohama City Fisheries Cooperative Association, the annual catch of P. yokohamae in Tokyo Bay exceeded approximately 500 t in the mid 1980s, but by the 2000s it had decreased substantially to around 50 t. Therefore, there is a need for elucidation of the cause of the decline of P. yokohamae for the recovery of the stock in the bay.To understand mechanisms of the population dynamics of P. yokohamae in Tokyo Bay, we have to clarify the critical life-history stage (or stages) that determine the year-class strength, and identify factors that affect mortality during the critical life-history stage, as well as consideration of changes in life history traits (e.g., reproduction), which may contribute to the population decline. In studying these matters, age and growth is one of important life history traits [4,5].For the estimation of age and growth, establishment of an accurate aging procedure is indispensable. Age and growth of P. yokohamae have p...
Eutrophication and hypoxia are major problems affecting the health of coastal ecosystems throughout the world. Tokyo Bay, Japan, is a eutrophic coastal area where the abundance of the megabenthic community has been decreasing. To assess factors associated with the impaired biota, seasonal surveys of the megabenthic community and water and sediment quality were conducted in the bay. Cluster analysis showed a difference in the community structure between the northern and southern parts of the bay. The density of species and species diversity were high throughout the year in the southern part of the bay, whereas in the northern part of the bay species diversity was low and defaunation occurred in August. At this time, bottom hypoxia due to temperature and salinity stratification, and high concentrations of nutrients, chlorophyll a, and organic matter in the water column and/or sediment, dominated the northern part of the bay. In October, bottom hypoxia was less severe but was still present in the northern part of the bay, and recolonization by mobile fishes and sessile mussels occurred. Multivariate analyses of the megabenthic community and environmental parameters in August showed the spatial pattern of the community could be explained by concentrations of dissolved oxygen and particulate organic carbon in the bottom water, and total sulfide and total organic carbon in the sediments. In particular, impairment of the biota in the northern area could be explained by the threshold concentrations of dissolved oxygen < 1.7 mL L(-1) and total organic carbon > 20.3 mg g(-1).
To explore which lifestages affect the stock size of young-of-the-year mantis shrimp Oratosquilla oratoria in Tokyo Bay, Japan, we investigated interannual variations in the quantitative relationships among egg production, larval density, and juvenile density. We collected adult females, larvae, and juveniles during monthly field surveys from 2004 to 2007. The interannual trend for the juvenile density index differed from those for egg production and larval density; although indices of both egg production and larval density were high in 2004 and 2007, the juvenile density index was high only in 2007, suggesting high mortality during the pelagic larval stage or the early phase of the postsettlement juvenile stage in 2004. We found that larval settlement started at the end of August and peaked in October, although larvae from the early spawning season (May-June) should have settled in August or earlier. Juveniles were found throughout the bay except in areas where bottom hypoxia occurred, suggesting that hypoxia restricts the spatial distribution of juveniles. Our results suggest that mortality during the early life history fluctuates among years, probably because of changes in environmental conditions in the bay, resulting in interannual variation in the stock size of youngof-the-year juvenile O. oratoria.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.