Assessment of Effects of UV Radiation on Marine Fish Larvae

Abstract

Uncertainties in estimating the biologically effective UV dose for northern anchovy larvae, Engraulis mordax are discussed including action spectrum used to weight UV dose, dose reciprocity, photorepair, relative sensitivity of life stages, and biological criteria for measuring UV effects. A preliminary estimate of UV induced losses to larval anchovy standing stock is presented. This calculation takes into account seasonal changes in larval abundance, UV radiation and average cloud cover, vertical distribution, and penetration of UV radiation into the habitat. The possible effects of ozone diminution on other populations of larval fish and the uncertainties in making an impact assessment on natural marine populations are discussed. Present evidence indicates that anchovy and other larval fish populations may be under some UV stress today but predicted levels of ozone diminution will probably not have a major effect on larval populations. Imprecisely defined habitat characteristics and the unknown effect of a small augmentation on high natural mortality rates are major barriers to accurate assessment of ozone decline on marine fish populations.