SynopsisVery little is known about the dynamics of native Hawaiian stream fishes. Five species are restricted, as adults, to freshwater streams and estuaries on the major islands of the Hawaiian archipelago. This paucity of information is partly due to difficulties inherent in determination of age and subsequent determinations of life history characteristics. In the present study, we determined the age of newly recruited Hawaiian gobies, Stenogobius genivittatus and Awaous stamineus using otolith microtechniques. Internal otolith increments were enumerated using scanning electron microscopy (SEM). Increments of newly recruited juveniles were deposited on a daily basis as validated through a marking study. Results showed recruitment at an average age of 135 and 161 days for these two species, respectively, with more rapid growth following recruitment to freshwater. Chemical analyses of otolith carbonate of the Hawaiian gobies by electron microprobe for strontium and calcium concentrations provided valuable insights into a fish's past history. A combination of structural and chemical analyses makes it possible to link growth and recruitment to nutritional and environmental factors. Such information developed as a broad model would be applicable to the management of Hawaiian gobies and would greatly improve the quality of information available for these unique fish populations and other fish populations.

Larvae of the Hawaiian amphidromous goby Lentipes concolor settled after a mean length of larval life (LLL) of 86·2 8·5 days (n=236, range=63-106 days) at a mean size of 16·0 0·7 mm L T (n=154, range=14·1-17·9 mm). Mean LLL for L. concolor was about twice that typically reported for tropical marine gobiids. Variation in LLL (CV=10%) and size at settlement (CV=4%) were low, and comparable to that for marine gobiids. LLL and L T were weakly positively correlated (Pearson's correlation coefficient r=0·50, P<0·0001). Larvae settled after shorter planktonic lives and at smaller sizes during months with warmer ocean temperatures. Inter-island variation in LLL did not support a dominant south-east to north-west larval drift, following the dominant south-east to north-west flow of prevailing currents in the Archipelago. Instead, recruits on Maui Island, centrally located in the archipelago, had shorter LLL than recruits to upstream Hawai'i and downstream Kaua'i islands. These findings have important implications for understanding the complex life history dynamics of amphidromous fishes as well as their management. 2001 The Fisheries Society of the British Isles

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We have applied a Sr/Ca ratio technique of otolith analysis to reconstruct the temperature histories of fall-spawned herring larvae Clupea harengus L. captured in inshore waters of the Gulf of Maine, USA, in order to infer their overwintering distributions. Winter survival of herring larvae is believed to be a determinant of recruitment in the Gulf of Maine, though very little is known about this important phase in their life history. Shortly after hatching in coastal spawning areas, larvae congregate inshore along the Maine coast during fall (September to November). Following this abundance peak, inshore larval densities drop to very low levels in mid-winter (late December and January), before a second group of fall-spawned larvae appears inshore in spring (February through April), thus giving a bimodal abundance distribution with time. We have inferred the overwinteriug distributions of larvae captured in the spring in the Sheepscot hver estuary, Maine, by analyzing changes in the concentrations ratios of strontium to calcium in the otoliths. These ratios vary as a function of temperature and thus act as a biological recorder of water temperatures experienced by an individual larva throughout its life history. Results suggest that the spring peak of herring larvae inshore represents larvae which overwintered offshore in the Gulf of Maine, implying that larvae w h c h enter the inshore nursery areas in the fall do not survive.

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SynopsisElemental analyses, using wave-length dispersive electron microprobe techniques on otoliths from reared Atlantic herring larvae, Clupea harengus, showed trace quantities of strontium relative to that of calcium, and an inverse relationship between Sr/Ca concentration ratios and rearing temperature. These data are consistent with those for coral aragonite, in that there appears to be an inverse temperature effect on physiological incorporation of strontium in the otolith aragonite. Our determinations of Sr/Ca concentration ratios of lab-reared herring larvae showed that the deposition of strontium relative to calcium and the rearing temperature were related, where: T ("C) = -2.955 [S&a] x 1000 + 19.172. This principle thus makes it possible to use Sr/Ca concentration ratios in fish otoliths to delineate past temperatures experienced by an individual. Further, combining electron microprobe analyses with scanning electron microscope (SEM) examinations of daily increments in the same otolith makes it possible to reconstruct the temperature history for an individual fish on a time scale of days. An example of the application of the technique to an approximately six-month-old field-caught herring larva is given, and the limitations of the technique are discussed.

A considerable aggregate of life-history, environmental and physiological information is incorporated within fish otoliths. This information may be discerned when appropriate analytical methods, based on an understanding of the mechanisms underlying changes in the structure and chemistry of otoliths, are utilized. Deposition of otolith carbonate may be regulated by many interacting factors, including age, physiology, environmental stress, availability of nourishment, ambient temperature, diurnal and seasonal cycles, and activity levels of individual fish. Complex interactions between genomic control and environmental conditions will ultimately govern depositional patterns.The chemical composition of otoliths is regulated by the physiological activity of fish, which in turn is influenced by environmental conditions. Interpretation of the chemical patterns in wild fishes must be validated by analysing the depositional patterns in fishes maintained under experimental conditions. Microchemistry analyses can provide life-history profiles and data on the environmental history of individual fish to clarify interpretation of age and growth trajectories. Several factors may contribute to the reported disparity in elemental studies, including suboptimal rearing environments, thermal effects on growth rate, and nutritional effects on otolith chemistry. Metabolic data describing growth and otolith crystallization obtained under artificial conditions that only grossly resemble the subtleties of the modelled environment may have a limited value and caution should be used when extrapolating results to natural systems. . On the forming season o f annual rings (opaque and translucent zones) in the otoliths o f several marine teleosts.