A reassessment of the fecundity type of Atlantic horse mackerel (Trachurus trachurus) in Atlantic Iberian waters (ICES division IXa) shows that indeterminate spawners can cease recruiting oocytes during their spawning season

Abstract

Following the classic lines of evidence of Hunter et al. (Hunter, J. R., Macewicz, B., Lo, N. C. H., and Kimbrell, A. 1992. Fecundity, spawning, and maturity of female Dover sole Microstomus pacificus, with an evaluation of assumptions and precision. Fishery Bulletin US, 90: 101–128.) on the fecundity type of fishes (determinate vs. indeterminate), the stock of horse mackerel (Trachurus trachurus) in Atlantic Iberian waters (ICES Division IXa) was shown to exhibit a mixed picture. Total fecundity, the total number of secondary growth (SG) oocytes dropped during the spawning season and there were reproductively active individuals with a distinct size hiatus between primary growth (PG) oocytes and SG oocytes, while no massive atresia was observed in late-season spawners. All of these characteristics matched with evidence for determinate fecundity. However, daily decrease rate of total fecundity was lower than daily specific fecundity (i.e. the number of eggs produced daily per unit weight) by orders of magnitude which suggested that the stock of SG oocytes was replenished during the spawning period through de novo oocyte recruitment. In addition, the maximum number of batches in reproductively active females was lower than the predicted annual number of spawnings, while total fecundity in recent spawners—those containing post-ovulatory follicles—was not lower than the fecundity of the remaining reproductively active females. All of these results suggest that, despite the aforementioned mixed lines of evidence, the fecundity of horse mackerel is clearly indeterminate. We attribute these mixed characteristics to the fact that, unlike most typical indeterminate spawners, horse mackerel ceases to recruit new SG oocytes during the latter part of its spawning season.

Ovarian dynamics and fecundity regulation in blueback herring, Alosa aestivalis , from the Connecticut River, US

“…Mopping‐up will only recover a portion of the energy that was invested in oocytes, representing a potentially expensive inefficiency. Some species, such as the Atlantic horse mackerel (Ganias et al., 2017) and the Gulf menhaden (Brown‐Peterson et al., 2017) modulate or avoid mopping‐up through a cessation of SG recruitment well before the end of spawning. In contrast, BBH in the Connecticut River, even though they continue to recruit SG oocytes throughout the spawning period, avoid massive atresia by reducing the intensity of SG recruitment as spawning progresses.…”

“…Ganias et al . (2017) report for the Atlantic horse mackerel ( Trachurus trachurus ) a cessation of SG recruitment and lack of massive atresia in late‐season spawners. A similar pattern has been suggested in Gulf menhaden, Brevoortia patronus (Brown‐Peterson et al., 2017).…”

Oocyte recruitment and fecundity type in fishes: Refining terms to reflect underlying processes and drivers

“…One such case is the Atlantic horse mackerel which additionally displays a seasonal drop in total fecundity without major resorption of oocytes (i.e. mass atresia) in late season spawners (Ganias et al., ). However, the maximum number of batches in spawning capable fish is much lower than the predicted annual number of spawnings (Ganias et al., ) which clearly suggests indeterminate fecundity type.…”

“…In addition, there is growing research on batch spawners showing the interactions between oocyte recruitment events, the oocyte growth period (the time it takes for SG oocytes to develop and complete vitellogenesis), and the duration of the spawning period [e.g. the Atlantic mackerel, Scomber scombrus, Scombridae (Greer‐Walker, Witthames, De Los, & Santos, ), the sole, Solea solea , Soleidae (Witthames & Greer‐Walker, ), and the Atlantic horse mackerel, Trachurus trachurus , Carangidae (Ganias, Mouchlianitis, Nunes, Costa, & Angélico, )]. Thus, to understand oocyte recruitment and its effect on fecundity type in batch spawners, it is important to understand drivers of spawning intervals, effects of temperature on oocyte growth, and the duration of spawning or spawning period at the individual scale.…”

“…As fisheries applied reproductive biology has become more process-oriented, and more in-captivity studies have been conducted, we are gaining a better understanding of the timing of events in oogenesis. Specifically, there is growing evidence that oocyte recruitment events are mediated by internal energetics and endogenous and exogenous cues, as well as species-specific feedback loops and environmental thresholds (Lowerre-Barbieri, Brown-Peterson et al, 2011 (Ganias, Mouchlianitis, Nunes, Costa, & Angélico, 2017)]. Thus, to understand oocyte recruitment and its effect on fecundity type in batch spawners, it is important to understand drivers of spawning intervals, effects of temperature on oocyte growth, and the duration of spawning or spawning period at the individual scale.…”