Time course of oocyte development in winter flounder Pseudopleuronectes americanus and spawning seasonality for the Gulf of Maine, Georges Bank and southern New England stocks

Abstract

Winter flounder Pseudopleuronectes americanus were collected at monthly intervals from December 2009 to May 2011, to describe the pattern and seasonality of oocyte development, including: (1) the group-synchronous transition from primary to secondary oocytes that initiates immediately after spawning, (2) the slow (months) development of vitellogenic oocytes followed by the rapid (weeks) maturation of oocytes, (3) the synchronous nature of mature oocytes ovulating, but the discrete releases of benthic eggs in batches, (4) the protracted (months) degradation of postovulatory follicles and (5) the occurrence of follicular atresia. Although fish were collected across only c. 2° latitudinal range, the spawning season was c. 1 month later in the Gulf of Maine (GOM) than on Georges Bank and in southern New England. This is probably due to lower temperatures in the GOM. These stock-specific data regarding the time course of oogenesis are of practical value. This information is discussed in relation to measuring and interpreting elements of reproductive potential such as maturation, skipped spawning and fecundity, the response of reproductive traits by this widely distributed species to changing climate and the response by this common, marine-estuarine species to urbanization, particularly environmental pollutants and dredging.

Investigating spatial variation and temperature effects on maturity of female winter flounder (Pseudopleuronectes americanus) using generalized additive models

“…Fixed ovarian tissue was prepared following a standard paraffin embedding protocol and stained using Schiffs-Mallory trichrome or hematoxylin-eosin (Press et al 2014). Prepared sections were viewed using a compound microscope (40×-100×) and staged following McBride et al (2013).…”

“…Prepared sections were viewed using a compound microscope (40×-100×) and staged following McBride et al (2013). Given that fish were sampled in close proximity to the peak spawning period, first-time maturing fish would not spawn until the following year because of the (approximate) 1-year time course of oocyte development (Press et al 2014). Therefore, we reduced the 10 maturity classes of McBride et al (2013) to two functional classes: immature (stages 1 and 2; Table 1) and mature (stages 3-10).…”

“…Fish at the southern end of the species' exploitable US range tend to grow faster and mature at earlier ages (estimated median age at maturity of 2.4 years) than those in the northern GOM (4.7 years; McBride et al 2013). The timing of spawning follows a similar gradient, with fish in SNE and GB stock areas spawning earlier in the species' winter-to-spring spawning season (November-April) than those in the GOM (April-June; Pereira et al 1999;Press et al 2014). These latitudinal trends continue into Canadian waters, where the median estimated age-at-maturity increases to 7.0 years for female flounder off of Newfoundland (Kennedy and Steele 1971).…”

Goosefish Lophius americanus fecundity and spawning frequency, with implications for population reproductive potential

“…The degradation rate of POFs is not known for L . americanus , but could range from as short as 1 day, which seems unlikely, to several weeks, which is more likely at winter–spring temperatures (Ganias, ; Press et al ., ). As a rough estimate, a 2 month period to create an egg veil would yield a maximum of four veils per year for an individual.…”

“…Collecting depths and latitudes varied between years (Table ), confounding these variables as main effects. Also, although a variety of fishes have lower fecundity at more northern latitudes (Press et al ., ; McBride et al ., ; McElroy et al ., ), L . americanus gonads in the northern management unit have not been examined and samples for both areas in the same year are probably needed to rigorously test for latitudinal effects.…”