Large annual variation in the amount of skipped spawning for female Northeast Arctic haddock Melanogrammus aeglefinus

Øystein Langangen,Jon E. Skjæraasen,Anders Frugård Opdal,Gjert Endre Dingsør,Christian Jørgensen,Knut Korsbrekke

doi:10.1016/j.fishres.2020.105670

Abstract

Although the phenomenon of skipped spawning has been described in numerous fishes, time-series are scarce. We used the presence of post-ovulatory follicles in histological gonad slides from females not developing oocytes for Northeast Arctic (NEA) haddock Melanogrammus aeglefinus from 2009 to 2012 to construct a length-based statistical model giving the probability that a non - developing female was skipping spawning, as opposed to not being sexually mature. This model was then applied on demographic winter survey data from the Barents Sea from 1989 to 2014. This indicated large annual variation in skipping numbers. Comparing these survey estimates to the total annual ICES stock numbers, we found that skipping peaked in the years 1994–1996 and 2009–2014, when the median yearly estimate of skipped spawners was 20–45 % of all females aged ≥ 3 years. In contrast, only ∼ 3 % of females at age ≥ 3 years skipped spawning in 2007. The proportional representation of skipped spawners at the stock level appeared linked to stock energy reserves with more skipping occurring when energy levels were low. Skipping also became more frequent with increasing population age, i.e. when immatures were less abundant, although the very largest/oldest fish tended to spawn. Because the proportion of NEA haddock that skips spawning is variable and can be high, understanding variation in this phenomenon and its drivers may improve population dynamic models.

Highlights

Skipped spawning, i.e. the phenomenon that animals do to not take advantage of every spawning opportunity following initial maturation, has received attention in marine fish in recent years (e.g. Jørgensen et al, 2006; Rideout et al, 2006; Rideout and Tomkiewicz, 2011; Skjæraasen et al, 2012)
We evaluated the relative role of stock energy reserves and demography in influencing the annual value estimated for skipped spawning by constructing two yearly proxies representing each of these facets and regression them against our yearly median estimates of females skipping spawning
By using demographic data and a detailed dataset on gonad histology, we infer the temporal dynamics of skipped spawning in female Northeast Arctic (NEA) haddock

Summary

Introduction

I.e. the phenomenon that animals do to not take advantage of every spawning opportunity following initial maturation (sensu Rideout et al, 2005), has received attention in marine fish in recent years (e.g. Jørgensen et al, 2006; Rideout et al, 2006; Rideout and Tomkiewicz, 2011; Skjæraasen et al, 2012). The first argues that individuals have insufficient energy reserves to complete maturation and spawning, and skip spawning to build reserves for the reproductive opportunity, typically the year in seasonal environments (Rideout et al, 2005). The second theory argues that skipped spawning represents an adaptive strategy for allocating energy towards length growth, which enhances fecundity later in life as well as individual lifetime reproductive success, it comes at a cost in terms of current reproduction (Jørgensen et al, 2006; Folkvord et al, 2014). For some cold-water teleosts these can Present address: Fiskebåt (The Norwegian Fishing Vessel Owners Association), Slottsgaten 3, N-5003, Bergen, Norway

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