Regional variation in larval retention and dispersal drives recruitment patterns in a temperate reef fish

Abstract

Although there is wide appreciation for the influence of variable larval transport on recruitment, few studies have investigated the relationship between recruitment intensity and the origin(s) of recruits. We evaluate this relationship for the common triplefin Forsterygion lapillum in Wellington Harbour (a semi-enclosed bay) and the adjacent open coast of North Island, New Zealand. As the harbour is productive, with many F. lapillum adults, we predicted the harbour would be an important source of recruitment for both regions. We estimated larval origins and dispersal histories using embryonic and larval otolith chemistry, respectively, with differences in otolith elemental composition consistent with birth and/or development in either harbour or open ocean waters. In the harbour, recruitment was greatest when locally spawned larvae were retained. Although large recruitment pulses to the open coast were comprised mostly of larvae originating from the open coast, 72% of all recruits to the south coast were actually spawned in the harbour. Dispersal of larvae from the harbour was frequent, but in low numbers, and was unrelated to opportunities for transport from the harbour. Given recent evidence for differences in larval growth between regions, we suggest that (1) faster larval growth combined with nearshore larval distributions result in high recruitment to the harbour and moderate, but demographically important, dispersal from the harbour to the open coast. In contrast, we suggest that (2) the combination of strong tidal currents in Cook Strait and slower larval growth result in lower recruitment and greater transport of larvae among open coast populations. The mechanisms that underlie such contextdependent dispersal have important implications for patterns of connectivity.KEY WORDS: Recruitment variability · Larval dispersal · Natal origin · Self-recruitment · Connectivity · Member-vagrant hypothesis · Drift -retention dichotomy · Reef fish Resale or republication not permitted without written consent of the publisher

Discordance between nuclear and mitochondrial DNA analyses of population structure in closely related triplefin fishes (Forsterygion lapillum and F. capito, F. Tripterygiidae) supports speciation with gene flow

“…Other studies on fishes have found variation in levels of differentiation across loci, with high gene flow overall but geographic structure at markers under selection, often termed 'islands of speciation' (Hemmer-Hansen et al 2013;Gaither et al 2015). In the present study, the differences in body morphometrics observed between individuals from exposed compared to sheltered locations within the Gulf (Croq 2009) are however more likely to be attributable to phenotypic plasticity (Sharpe et al 2008), or differential larval nutrition (Swearer and Shima 2010). Considering phenotypic plasticity, the trend towards a greater robustness in body shape in F. lapillum individuals at more exposed sites could suggest adaptive plasticity, analogous to coral reef fish populations across an exposure gradient (Fulton et al 2013).…”

Subtle genetic structure reveals restricted connectivity among populations of a coral reef fish inhabiting remote atolls

“…Although these larval characteristics may promote long‐distance dispersal, fish larvae are clearly not passive particles; they can orientate themselves vertically in the water column, sustain swimming speeds that are faster than average current speeds, and can sense and swim toward reefs (Leis 2010). Considerable evidence is accumulating that these behaviors contribute to self‐recruitment in many tropical (e.g., Doherty et al 1995; Almany et al 2007; Gerlach et al 2007; Paris et al 2007) and temperate fish species (e.g., Carreras–Carbonell et al 2007; Galarza et al 2009; Swearer and Shima 2011).…”

Evidence and population consequences of shared larval dispersal histories in a marine fish

“…). Our own work on a small reef fish, the common triplefin ( Forsterygion lapillum ), suggests that variation in larval dispersal histories can have significant demographic consequences by affecting the number (Shima and Swearer , Swearer and Shima ) and phenotypes (Shima and Swearer ) of fish that replenish local populations, with flow‐on effects to juvenile growth and condition (Shima et al. ), survival to adulthood (Shima and Swearer ), population stability (Noonburg et al.…”