Critical timing for reproductive allocation in a capital breeder: evidence from sandeels

Abstract

Life-history theory predicts a tradeoff in resource allocation between early maturation and growth in species which exhibit indeterminate growth. However, since life-history models assume that the fitness payoff of each developmental strategy at completion is known, they are unable to encapsulate the mechanics by which maturation is controlled under natural conditions. To determine the proximate conditions which influence variation in reproductive investment, we recorded somatic growth, sexual maturation and fecundity in individually marked first-time maturing lesser sandeels Ammodytes marinus. Cytological investigation revealed that the transition in gonad development from primary to secondary stages occurred between June and August in both sexes. Using logistical regression, variation in maturation could be attributed to both initial weight and observed differences in resource accrual during this period, suggesting that if growth prior to this period is inadequate in smaller fish then maturation remains inhibited. For those females that did mature, potential fecundity positively correlated with final body size. Our findings indicate that small changes in the timing of the availability of their zooplankton prey could explain the large regional variability in maturity at age exhibited by sandeels in the field.

Effects of copepod size on fish growth: a model based on data for North Sea sandeel

“…Further details about model parameters are summarized in Table 1. Energy intake was predicted for different sizes of sandeel, ranging from newly metamorphosed sandeels of 5 cm (Wright & Bailey 1996) all the way to 17 cm, which is the maximum attainable length of lesser sandeels in the central North Sea (Boulcott & Wright 2008, Jensen et al 2011). Our analysis focused on 2 distinct size groups of copepods, viz.…”

Reproductive strategy of forkbeard, Phycis phycis, from the Portuguese coast

“…Atlantic cod [72]; black scabbardfish Aphanopus carbo Lowe, 1839 [14,50]; and European seabass Dicentrarchus labrax (Linnaeus, 1758) [43]), and it is assumed that species with determinate fecundity are strongly associated with capital breeding behaviour [44]. In determinate species, the reproductive investment is heavily dependent on the feeding season prior to the major yolk production that takes place during vitellogenesis [5]; however, batch spawning can reduce the energy initially required for spawning [44]. The forkbeard seems to have a mixedbreeding strategy, since feeding is common during late vitellogenesis but may also take place during parts of the spawning season (Ana R. Vieira 2012, personal observation).…”

Confusion Reigns? A Review of Marine Megafauna Interactions with Tidal- Stream Environments

“…Individuals show significant weight loss during this period (Boulcott et al 2007, Boulcott & Wright 2008, and it is speculated that increased temperature will increase this rate of loss due to elevated metabolism. The energy reserves required to sustain the animals through the winter fast must be accumulated the previous summer, so unless warming is accompanied by increased scope for summer feeding, which does not appear to be the case , Boulcott et al 2007, then the net effect is likely to be reduced overwinter survival (Van Deurs et al 2011).…”