Effect of type of otolith and preparation technique on age estimation of larval and juvenile spot (Leiostomus xanthurus)

Otoliths of larval and juvenile fish provide a record of age, size, growth, and development (Campana and Neilson, 1985; Thorrold and Hare, 2002). However, determining the time of first increment formation in otoliths (Campana, 2001) and assessing the accuracy (deviation from real age) and precision (repeatability of increment counts from the same otolith) of increment counts are prerequisites for using otoliths to study the life history of fish (Campana and Moksness, 1991). For most fish species, first increment deposition occurs either at hatching, a day after hatching, or after first feeding and yolksac absorption (Jones, 1986; Thorrold and Hare, 2002). Increment deposition before hatching also occurs (Barkmann and Beck, 1976; Radtke and Dean, 1982). If first increment deposition does not occur at hatching, the standard procedure is to add a predetermined number to increment counts to estimate fish age (Campana and Neilson, 1985)

Relationships between Larval and Juvenile Abundance of Winter-Spawned Fishes in North Carolina, USA

We analyzed the relationships between the larval and juvenile abundances of selected estuarine-dependent fishes that spawn during the winter in continental shelf waters of the U.S. Atlantic coast. Six species were included in the analysis based on their ecological and economic importance and relative abundance in available surveys: spot Leiostomus xanthurus, pinfish Lagodon rhomboides, southern flounder Paralichthys lethostigma, summer flounder Paralichthys dentatus, Atlantic croaker Micropogonias undulatus, and Atlantic menhaden Brevoortia tyrannus. Cross-correlation analysis was used to examine the relationships between the larval and juvenile abundances within species. Tests of synchrony across species were used to find similarities in recruitment dynamics for species with similar winter shelf-spawning life-history strategies. Positive correlations were found between the larval and juvenile abundances for three of the six selected species (spot, pinfish, and southern flounder). These three species have similar geographic ranges that primarily lie south of Cape Hatteras. There were no significant correlations between the larval and juvenile abundances for the other three species (summer flounder, Atlantic croaker, and Atlantic menhaden); we suggest several factors that could account for the lack of a relationship. Synchrony was found among the three southern species within both the larval and juvenile abundance time series. These results provide support for using larval ingress measures as indices of abundance for these and other species with similar geographic ranges and winter shelf-spawning life-history strategies

Temperature and salinity effects on strontium incorporation in otoliths of larval spot (Leiostomus xanthurus)

Author Posting. © National Research Council Canada, 2004. This article is posted here by permission of National Research Council Canada for personal use, not for redistribution. The definitive version was published in Canadian Journal of Fisheries and Aquatic Sciences 61 (2004): 34-42, doi:10.1139/F03-143.Temperature dependence of strontium/calcium (Sr/Ca) ratios in foraminiferal calcite and coral aragonite is well established; however, factors controlling Sr/Ca ratios in fish otoliths remain obscure. To assess temperature dependence of Sr/Ca in marine fish otoliths, we reared spot (Leiostomus xanthurus) larvae under controlled temperature (17–26 °C) and salinity (15‰ and 25‰). We found a significant linear relationship between temperature and Sr/Ca ratios, with a sensitivity of approximately 5%·°C–1. Otolith Sr/Ca values were also significantly higher at a salinity of 25‰ vs. 15‰, after accounting for differences in dissolved Sr/Ca ratios in the ambient water, with a sensitivity of approximately 1%/salinity (‰). These observations complicate the use of Sr/Ca ratios to determine temperature histories of spot larvae, because accurate temperature reconstructions are possible only with a priori knowledge of both ambient salinity and dissolved Sr/Ca ratios. Fully marine species residing in oceanic waters will not experience significant salinity variations; therefore, otolith Sr/Ca ratios may be useful recorders of temperature exposure. Otolith Sr/Ca thermometry in coastal fish species that make regular excursions into estuarine waters will be more problematic. Multiple geochemical tracers, including oxygen stable isotopes and other trace elements, may be necessary to accurately reconstruct temperature and salinity histories in these species.This research was supported by grants from the National Science Foundation to S.R.T. (OCE-0134998) and to S.R.T. and C.M.J. (OCE-9876565), a grant in aid to G.B.M. from the International Women’s Fishing Association, and a PEO International Women’s Organization Scholar Award to G.B.M