Selective mortality during the larval and juvenile stages of snappers (Lutjanidae) and great barracuda Sphyraena barracuda 

Abstract

Selective mortality during the early life stages in marine organisms can affect the magnitude and composition of recruitment, yet these processes have not been examined in economically important predatory coral reef fishes. Utilizing 3 different stage-specific sampling techniques (shipboard plankton tows, larval light traps, juvenile surveys/seines), we repeatedly sampled multiple cohorts of 3 lutjanid (Ocyurus chrysurus, Lutjanus synagris, and L. griseus) and 1 sphyraenid (Sphyraena barracuda) species through time in the Florida Keys (USA). Comparisons of daily growth and size-at-age (from otolith microstructure analysis) for early-and late-stage larvae and young and older juveniles revealed that size-and growth-selective processes operate during the larval stage, while after settlement, growth-selective mortality occurred in the absence of significant size differences. In all 3 lutjanid species, larvae and juveniles that were larger at hatch preferentially survived. In O. chrysurus and L. synagris, selective mortality of smaller, slowergrowing individuals during the larval stage reduced variability in these traits such that larvae were of similar sizes at settlement. Following settlement, patterns of growth-selective mortality were initially opposite (favoring faster juvenile growth in L. synagris, and slower growth in O. chrysurus), but ultimately survivors of both species grew faster, leading eventually to a size advantage. In contrast, patterns of selective mortality were not evident until settlement in L. griseus and S. barracuda, and favored larger and smaller sizes-at-settlement, respectively. Overall, our results reveal important patterns of selective mortality and variability between even closely related species.

Larval traits show temporally consistent constraints, but are decoupled from postsettlement juvenile growth, in an intertidal fish

“…for small larvae (Gaines & Roughgarden, 1987;Paradis et al, 1996); therefore, reducing the larval duration might have fitness benefits (Pechenik, 1999;Pepin & Myers, 1991). Other marine studies have reported the importance of hatch size on postsettlement mortality (D'Alessandro et al, 2013;Raventós & Macpherson, 2005), suggesting potential carry-over effects of maternal investment. However, in this study, path analyses revealed no effect of hatch size on postsettlement growth (Figures 2 and 3); size-at-settlement and size-4-days-postsettlement were also uncorrelated with hatch size, despite their measurements containing hatch size variation (Supporting Information Figure S2), indicating that variable growth mitigates later size consequences of maternal investment.…”

“…Studies of life-history trait distributions between life stages have revealed that fitness after metamorphosis can depend on trait variation and developmental environments in the larval phase (Allen & Marshall, 2010;Marshall & Keough, 2003;Raventós & Macpherson, 2005;Shima & Swearer, 2010), which is contrary to predictions of independent fitness consequences in complex life cycles. Therefore, the demographic properties of marine populations might be strongly governed by early developmental processes (Bergenius, Meekan, Robertson, & McCormick, 2002;D'Alessandro, Sponaugle, & Cowen, 2013;Hamilton, Regetz, & Warner, 2008;Searcy & Sponaugle, 2001;Shima & Swearer, 2010;Torres et al, 2016). For example, Gagliano, McCormick, and Meekan (2007) showed that selective mortality in a damselfish-occurring weeks to months after settlement-can be traced back to variation in hatch size or pelagic growth.…”

“…(Allen & Marshall, 2010;Holmes & McCormick, 2006), and hence, the ability to rapidly compensate for poor larval growth may be important if there is strong size-dependent postsettlement selection. Nonetheless, there can be costs associated with compensation mechanisms (Campero et al, 2008a), and conflicting selection across multiple paths to fitness (Crean et al, 2011; Marshall & Morgan, 2011) may govern their presence or absence.…”

“…Understanding how early developmental and environmental experiences shape life-history trait variation, and influence population dynamics, has been the focus of a large number of studies, particularly in marine systems (Allen & Marshall, 2010;Hamilton et al, 2008;Pechenik, 2006;Shima, Noonburg, & Swearer, 2015;Shima & Swearer, 2009;Sponaugle, Grorud-Colvert, & Pinkard, 2006;Torres et al, 2016). Such studies have been concerned with changes in population trait means over life stages and less well studied is the extent to which traits expressed at different life stages share variation (covary), the fitness consequences of covariance across stages and processes that modulate these relationships (Aguirre et al, 2014;Crean et al, 2011;Marshall & Morgan, 2011).…”

“…Furthermore, traits expressed at one life stage can have opposing effects on fitness in subsequent life stages (Miles & Wayne, 2009;Schluter, Price, & Rowe, 1991). For example, Crean, Monro, and Marshall (2011) identified conflicting selection with regard to larval growth rates in an ascidian. Larvae with slower growth rates had greater survival to reproduction, but these individuals attained smaller average size at reproduction (which was expected to influence fecundity) relative to those individuals that grew more rapidly as larvae.…”