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SynopsisA further occurrence of Atherina boyeri in British waters is recorded. This species has a distribution which can be broadly defined as Mediterranean but has been occasionally recorded in waters which are beyond the northerly limits of its normal range. These records have usually been associated with localised thermal pollution but, at Oldbury-upon-Severn, England, this is probably not so. Morphometric and meristic data are presented which show clearly that this is a genuine record of A. boyeri. The existence of this species in waters with minimal, if any, thermal enrichment raises interesting questions regarding its distribution.This example and the other abnormal records of A. boyeri are, therefore, considered in relation to a number of environmental parameters. The parameters discussed, namely increased water temperature, decreased salinity and lagoon conditions have all been implicated in previous records.The conclusion tentatively reached is that A. boyeri is capable of surviving under a cooler temperature regime than that with which it is normally associated. Normally its range is restricted by inter-specific competition. In conditions of calmer water, however, in which there is also reduced salinity it is able to compete and maintain itself successfully.

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Gravid sandsmelt, Atherinu presbyter, were captured from Langstone Harbour, Hampshire, during 1978. They were maintained under laboratory conditions where spawning took place. The egg and its embryonic development are described. From fertilization to hatching took 26-27 days at 15" C and 13-1 5 days at 20" C. The newly hatched postlarvae were 6.5 to 7.2 mm long. Postlarvae 10.7, 13.4, 15.4 and 19.0 mm taken from the same locality are described and compared with previous descriptions. Their occurrence confirms successful spawning in the central English Channel.