Reproductive strategies and early development of three freshwater gobies

Abstract

Three species of gobiid fish inhabit the freshwater Lake Trichonis of western Greece. Two of these species, Economidichthys pygmaeus and E. trichonis are endemic, and the third is the widespread Knipowitschia caucasica. There are habitat separations between the three species, E. pygmaeus and E. trichonis prefer vegetated areas, the first being fully demersal at all stages of development and the second being semi‐demersal. Knipowitschia caucasica prefers sandy bottoms and is distributed in shallower waters. Female E. pygmaeus and E. trichonis spawn in nests prepared by the males in the cavities of broken reeds. The males subsequently guard the eggs until they hatch, with females playing no role in parental care. Economidichthys trichonis is probably the smallest freshwater European species. Its eggs are ovoid, measuring about 0.64 × 0.58 mm, from which tiny, unpigmented and incompletely developed pelagic larvae hatch out after an incubation period lasting less than 1 day at a water temperature of 19.5° C. The eggs of E. pygmaeus are cylindrical and larger, measuring about 2.38 × 0.89 mm, from which relatively large, strongly pigmented and ontogenetically more advanced larvae hatch out after a longer incubation period. Both species reproduce only once in their lifetime, at the age of 1 year, and die shortly after spawning, but the breeding season involves several spawnings by each individual fish. These biological, developmental and reproductive characteristics are discussed in relation to current theories on evolution of life‐historics.

Reproductive biology ofAwaous guamensis, an amphidromous Hawaiian goby

“…Miller (1984) notes that nearly all gobies practice repeat spawning. Even gobies which are essentially 'annuals', dying after their first breeding season, produce more than a single clutch (Daoulas et al 1993). Our results indicated that A. guamensis females probably produce only a single clutch each season.…”

Fish predation in the proximity of purse seine fishing lights: The case of Atherina boyeri (Actinopterygii: Atheriniformes: Atherinidae) in a Greek Lake

“…Although there are no estimates of the current population size of E. trichonis in Lake Trichonis, the predation of its larvae by another fish species due to the use of fishing lights may pose a conservation issue. However, from August onward, the contribution of E. trichonis larvae in the diet of A. boyeri decreased considerably, probably due to the maturation of the former in autumn and the alteration of their distribution pattern from the planktonic to the benthic state (Daoulas et al 1993). Considering also that the purse seine fishing of A. boyeri is prohibited for nearly a summer month (15 of June to 20 of July) in order to protect its breeding, the impact of fisheries to E. trichonis larvae could be insignificant.…”

“…All prey items within the stomach contents of each specimen containing food were identified under a stereoscope to the lowest taxonomic level possible, given the degree of digestion. Identification of the fish larvae recovered from the stomach contents and being in fairly good condition (not showing pronounced digestion) was based on the morphological descriptions provided by Daoulas et al (1993).…”

Life cycle of the pelagic goby Aphia minuta (Pisces: Gobiidae)

“…The disappearance of A. minuta inside the bays suggests either that they had migrated elsewhere after spawning, or that a high proportion had died. Mortality after the first and only period of spawning occurs in several gobies (Bouchereau et al, 1989;Daoulas et al, 1993).…”