Birth-date selection in early life stages of plaice Pleuronectes platessa in the eastern Irish Sea (British Isles)

Abstract

For species with extended spawning seasons, short periods of beneficial conditions often lead to disproportionate survival of sub-sets of the offspring. This has been demonstrated for freshwater fish and for marine pelagic species, but has been less frequently tested for other teleost groups. Using offshore plankton surveys, we constructed egg production curves for plaice Pleuronectes platessa L. in the eastern Irish Sea. Data from 5 yr showed that spawning began sometime before January and was completed by the end of April. Over these years the timing of peak spawning varied between mid-February and mid-March. In 2001, 2002 and 2003, we also sampled postsettlement plaice from inshore nursery grounds. Otolith micro-increment analyses and temperaturedependent egg development rates were used to back-calculate the birth dates of the settled fish. By June, immigration to the nursery grounds was largely completed and the shape of the reconstructed birth-date distributions corresponded closely to the relevant egg production curves. In contrast to many other studies, there was little evidence for significantly disproportionate survival of specific portions of the egg production curve between spawning and the recently post-settled stages. Such a survival pattern could be generated by a gradual switch from starvation to predation as the principal cause of larval mortality as the spawning season progressed.

Patterns of variability in early-life traits of fishes depend on spatial scale of analysis

“…Defining variability in spawning date and PLD at multiple scales (both temporal and spatial), therefore, can be pivotal to proper delineate connectivity patterns at larval stages and provide effective clues for management (i.e. design of marine reserve networks, [11]). Spatial variability in early-life traits A.…”

“…The identification of spawning dates has been the subject of a number of studies that have seldom assessed variability in time (i.e. interannual variability, [11]) and space [2], but, as far as we know, no study has assessed variability over multiple scales.…”

Variability in transport of fish eggs and larvae. IV. Interannual variability in larval stage duration of immigrating plaice in the Dutch Wadden Sea

“…Preparation of the otoliths was carried out according to standard techniques as described in (2000b). Series of light micrographs at magnifications between 100× and 2500× were used for increment analysis covering the area from the hatch ring to the metamorphosis ring, representing the pelagic period (Ryland 1966, Fox et al 2007. At least 4 counts of the number of daily increments were made along various radial lines from the first visible increment.…”

“…In North Sea plaice, an inverse relationship has been found between the number of settling larvae in the western Wadden Sea and the median water temperature during the pelagic period, both within and between years (van der Veer & Witte 1999), whereas for Irish Sea plaice no birth-date selection in early life stages has been observed (Fox et al 2007). The synchrony in plaice recruitment around the United Kingdom and its negative relationship with seawater temperature is consistent with the hypothesis that temperature affects predation processes during the larval planktonic stage (Fox et al 2000).…”

Identification of marine fish egg predators using molecular probes

“…In addition, we assume that consumption of adult plaice by the suite of potential predators that we assayed would not occur, or would be obvious during dissection of predator stomachs. Because plaice spawning occurs offshore, but nursery grounds are inshore (Fox et al 2007), we also assume that small, juvenile plaice were not present in the study area. Although remains of plaice eggs can be visually identified in teleost stomachs (Ellis & Nash 1997), we wanted to test the molecular approach as an alternative meth od for rapid screening of large numbers of potential predators and to identify any non-teleost predators consuming plaice eggs/larvae in the study area.…”