Fecundity of Sebastes mentella and Sebastes norvegicus in the Irminger Sea and Icelandic waters

Abstract

Fecundity of redfish Sebastes mentella and Sebastes norvegicus in the Irminger Sea and Icelandic waters was analyzed in relation to several maternal features and oocyte developmental stages. The mean potential fecundity in S. norvegicus was estimated to be 123,300 oocytes and relative fecundity averaged 116 oocytes g-1. Mean potential fecundity in S. mentella was 50,013 oocytes and relative fecundity was 64 oocytes g-1. Strong fecundity down-regulation (50% on average) was observed during oocyte development estimated from September to November, when oocytes reached the advanced stage of vitellogenesis. This result implies that fecundity can only be comparable between individuals presenting the same stage of oocyte development. However, the development rates differed between species and between stocks, and therefore the same stage is reached at a different time of the year. Fecundity varied significantly with female weight and length, while condition had little influence on fecundity variation.

Intra- and interannual variation in fecundity and egg size of lumpfish (Cyclopterus lumpus) in Iceland

“…Carcass weight was the best predictor of fecundity and notably outperformed length. This result is consistent with findings from other studies of fish fecundity that indicate that body weight is generally a better predictor of fecundity than length (Koops et al, 2004;Rideout and Morgan, 2010;Tanaka et al, 2017). The addition of liver weight explained only a small percentage of the variation in fecundity.…”

“…The addition of liver weight explained only a small percentage of the variation in fecundity. This finding corresponds with those of previous studies in which characteristics intended to measure "condition," or energy reserves, added little in comparison to the factors reflecting body size (Alonso-Fernández et al, 2009;Rideout and Morgan, 2010;Rogers et al, 2019). The reason that such indices of energy reserves have a minor effect on explained variance is likely that, when sampling fish close to spawning, the energy to be used for ovary development has already been transferred from storage to the gonads.…”

“…However, greater lifetime fecundity may not translate into greater numbers of surviving offspring because mortality of lumpfish in early life stages may not be equal through the spawning season as a result of differing environmental conditions, prey availability, or predation (Methot, 1983;Narimatsu and Munehara, 1999;Voss et al, 2006). Although there was interannual variability in the fecundity of lumpfish, the variability during 2009-2019 was low in comparison with the variability observed in other long-term studies of fish fecundity (Kjesbu et al, 1998;Kennedy et al, 2007;Rideout and Morgan, 2007). The extent to which fecundity varies between years in fish species is poorly understood because of a limited number of multiyear studies.…”

“…Because fecundity is not routinely estimated, fecundity estimates from a single year, or a small number of years, may be used to estimate annual changes in total egg production (Gundersen et al, 2000;Blanchard et al, 2003;Mehault et al, 2010). This use of temporally limited fecundity data may be problematic because of potential variability in fecundity between years (Rideout and Morgan, 2007). The lumpfish (Cyclopterus lumpus) ( Fig.…”

New insights in oocyte dynamics shed light on the complexities associated with fish reproductive strategies

“…Down-regulation of the more advanced oocytes is often seen as a process of matching the available energy 49 . Intense atretic activity was observed both in this and earlier studies on hake 24,50 , but only after the spawning season ceases, with the possible exception of summer time where atresia coincided with the spawning peak.…”