Recruitment implications of larval herring overwintering distributions in the Gulf of Maine, inferred using a new otolith technique

Abstract

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.

Chemistry and composition of fish otoliths:pathways, mechanisms and applications

“…Despite the initial promise, otolith Sr:Ca ratios do not appear to reflect temperature in a consistent manner. As noted in the section 'Temperature', temperature reconstructions based on Sr:Ca have performed well in only a handful of coldwater examples (Townsend et al 1989, Radtke et al 1990, and are readily confounded by changes in salinity. However, oxygen isotope ratios do not appear to suffer the same constraints, and their relationship to temperature has been experimentally validated in several fish species (Kalish 1991c, Thorrold et al 199713).…”

“…However, a crystallization process which is controlled by the rate of matrix protein formation, and inversely proportional to otolith Sr:Ca, is consistent with most of the observations. Since the rate of protein synthesis is often highly correlated with metabolic rate, temperature and somatic growth rate, explanations for presumed temperature (Radtke 1989, Townsend et al 1989 and growth rate effects (Sadovy & Severin 1992) on otolith Sr:Ca become readily apparent. However, the link between temperature and protein synthesis often fails at higher temperatures, due to higher metabolic losses.…”

“…Examples of otolith elements influenced by temperature include Mg (Fowler et al 1995a Temperature itive (Kalish 1989, Arai et al 1995, Fowler et al 1995a. Limburg 1996, negative (Townsend et al 1989, Radtke et al 1990, Sadovy & Severin 1992, Secor et al 1995b, and non-existent (Gallahar & Kingsford 1996, Tzeng 1996 correlations with temperature have been reported. A meta-analysis of the existing literature does not support an overall relationship between otolith Sr:Ca and temperature for either saltwater or freshwater fish (Fig.…”

Drastic changes in otolith strontium/calcium ratios in leptocephali and glass eels of Japanese eel Anguilia /aponica

“…Our examination of the otolith increment width also showed the similar pattern at ages 80 to 110 d, coincident with the ages at which both Sr content and Sr/Ca ratios changed dramatically. In various marine fishes, otolith Sr/Ca ratios have been reported to be inversely related to ambient water temperature (Radtke & Targett 1984, Radtke 1989, Townsend et al 1989, 1992, Radtke et al 1990). In contrast, the eel otolith Sr/Ca ratios decreased in the period when metamorphosing leptocephali possibly experienced rapid decrease in ambient water temperature.…”

Elemental signatures in bone to determine life history characteristics in fish.

“…Seasonal changes in reproductive physiology have resulted in variations in SnCa ratios (Kalish 1991). In addition, temperature changes in the ambient environment have resulted in changes to the Sr:Ca ratios (Townsend et al 1989;Townsend et al 1995). However, the magnitude of the changes in Sr:Ca ratios when fish migrate from freshwater to seawater are so much greater than variations due to physiology change or temperature.…”