Variation in pelagic larval growth of Atlantic billfishes: the role of prey composition and selective mortality

Larval ecology of a suite of snappers (family: Lutjanidae) in the Straits of Florida, western Atlantic Ocean

“…The idea of horizontal distributions of larvae reflecting adult distributions is not novel for snappers and was suggested by Powles (1977). Our data are consistent with this concept, suggesting that larval distributions mirror adult distributions in both horizontal and vertical dimensions.171 Mar Ecol Prog Ser 410Instantaneous larval growth rates (K ) were similar among species and regions in this study, but were markedly lower than larval growth rates of Atlantic blue marlin Makaira nigricans (K = 0.110; age range: 1 to 20 d) and sailfish Istiophorus platypterus (K = 0.134; age range: 2 to 18 d) from the same ichthyoplankton samples (Sponaugle et al 2010), or Rhomboplites aurorubens larvae (K range: 0.087 to 0.115; age range: 5 to 14 d) collected in the Gulf of Mexico (Comyns et al 2003). However, these differences are probably species-specific as growth rates presented here were similar to larval growth rates of laboratory-reared larvae of Lutjanus analis (K = 0.071, Clarke et al 1997), L. synagris (K = 0.064, Clarke et al 1997) and Ocyurus chrysurus (K = 0.036, Riley et al 1995; K = 0.0618, Clarke et al 1997) that were held at temperatures of 27.0 to 28.5°C, similar to those our larvae experienced.…”

“…In addition, temperature variability in the upper 50 m of the water column between east and west SOF was low (~2°C) during the truncated spawning season of the study species and tended to be ~0.2°C lower in the west during the 2 yr study (west: 26.97 ± 0.08°C; east: 27.24 ± 0.08°C), a difference that would have caused reduced, rather than increased larval growth. Higher mortality rates in conjunction with selection for slowgrowing larvae in the west may have contributed to faster growth rates; however, mortality rates were equivalent between regions, precluding this scenario.Growth of bluehead wrasse Thalassoma bifasciatum larvae and small (< 9 mm SL) zooplanktivorous Makaira nigricans larvae was also higher in the western SOF (Sponaugle et al , 2010. Faster growth was correlated with fuller guts and higher abundances of primary prey items (Farranula, harpacticoid and Oncaea copepods) in the west SOF for T. bifasciatum ) and with a higher proportion of Farranula relative to Evadne copepods in M. nigricans (Sponaugle et al 2010).…”

“…The strong unidirectional nature of the FC results in larvae of different ages captured along the transect at the same time potentially having different origins and early growth environments (older larvae may have originated farther upstream). To minimize this potentially confounding effect, a mean of the 3 d of growth before capture was calculated for each larva (excluding the marginal increment) and these data were tested for differences between eastern and western stations by means of ANCOVA with water temperature and larval age included as covariates to account for their effect on larval growth (Sponaugle et al 2010).…”

“…The strong unidirectional nature of the FC results in larvae of different ages captured along the transect at the same time potentially having different origins and early growth environments (older larvae may have originated farther upstream). To minimize this potentially confounding effect, a mean of the 3 d of growth before capture was calculated for each larva (excluding the marginal increment) and these data were tested for differences between eastern and western stations by means of ANCOVA with water temperature and larval age included as covariates to account for their effect on larval growth (Sponaugle et al 2010).Overall larval growth of the analyzed species was modeled with length-at-age data and the Laird-Gompertz growth equation (Nielsen & Munk 2004):where L t is length at time t, L 0 is length at hatching, g 0 is specific growth rate at hatch, and α is the rate of exponential decay of the specific growth rate. Due to a lack of newly hatched (age 0 d) and very young larvae (ages 1 to 7 d) in the samples, size-at-age data were not used to calculate L 0 .…”

A comprehensive view of the early life of the great barracuda: editorial comment on the feature article by D’Alessandro et al.

“…1). Their study was part of a larger, 2-year field sampling program examining monthly changes in the abundance, distribution, and diets of ichthyoplankton along a transect spanning the Gulf Stream in the Straits of Florida (Western Atlantic) (Richardson et al 2010;Sponaugle et al 2010). What makes the present study stand apart from many others dealing with ichthyoplankton ecology is the broad scope of information that it provides including seasonal changes in horizontal and vertical distribution, ontogenetic changes in diets, and rates of growth and mortality of larvae.…”