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

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Atlantic blue marlin (Makaira nigricans) and sailfish (Istiophorus platypterus) larvae were collected from 10monthly cruises (June–October 2003 and 2004) across the Straits of Florida to test (1) whether growth differed between the more productive western region near the Florida shelf, and the less productive eastern region toward the Bahamas, and (2) whether growth was related to prey consumption. Examination of larval sagittal otoliths revealed that instantaneous growth and daily growth during the first 2–3weeks of life did not vary significantly between the two regions for either species. However, recent growth during the last two full days prior to collection was greater in the west for blue marlin larvae. Recent growth of blue marlin larvae<9mm SL (primarily zooplanktivorous) was significantly related to prey composition (faster growth when higher proportions of Farranula copepods were consumed). Western larvae grew faster and had higher proportions of Farranula in their guts. Trends for sailfish larvae were not significant. In both species, comparison of early growth between<9 and≥9mm SL size groups indicated that growth trajectories diverged around 5–8mm SL, the time when billfish larvae become capable of piscivory. Significantly faster growth of larger (older) larvae suggests that mortality was selective for fast growers and that the transition to piscivory may be a critical point in the early life of billfish.
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... Beyond total carbon ingested, a proxy for energy intake, feeding success is also modulated by the capacity of ingested prey taxa to provide the suite of essential nutrients, such as amino acids and fatty acids, that are necessary for proper larval development (Rønnestad et al., 1999;Sargent et al., 1999). The larval prey field is composed of various taxa characterized by differences in potential to fulfill requirements relative to energy and essential nutrient intake, which likely explains why several larval fish species have been shown to selectively consume prey taxa that result in their optimal growth (Robert et al., 2009;Sponaugle et al., 2010;Murphy et al., 2013). These considerations make it important to identify larval fish prey to the lowest taxonomic resolution possible. ...
... While relatively few studies have empirically demonstrated a relationship between feeding success and growth in larval fishes (Dower et al., 2009;Robert et al., 2014b;and Pepin et al., 2015), even fewer studies have investigated the relationship between growth and the contribution of preferred prey to feeding success (Robert et al., 2009;Sponaugle et al., 2010;Murphy et al., 2013). The paucity of knowledge of larval prey preferences from highly resolved taxonomical information, and how this absence of data may be affecting our capacity to predict recruitment, has been increasingly acknowledged in recent years (St. ...
... John et al., 2001;Robert et al., 2014a). A positive relationship between consumption of a larva's preferred prey and recent growth has been documented for fish species inhabiting various environments (Atlantic mackerel, Robert et al., 2009; Atlantic blue marlin [Makaira nigricans], Sponaugle et al., 2010;snapper [Chrysophrys auratus], Murphy et al., 2012). In both Atlantic mackerel and blue marlin, consumption of the preferred prey during early larval development, before the onset of piscivory, determined whether an individual would be characterized by fast or slow growth trajectory during the next stages of development (Robert et al., 2009;Sponaugle et al., 2010). ...
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... A distinctive feature of this species was the occurrence of two microstructural zones in otoliths: a first zone where primary increments were more homogeneous and easy to identify, in contrast with a second zone where ring's alignment and other perturbations predominated. Microstructural zones in sagittal otoliths of YOY have been reported in several teleost fish (Wellington and Victor 1989;Beldade et al. 2007;Sponaugle et al. 2010;Garcia-Seoane et al. 2015), particularly in demersal and reef-associated fish (Victor 1986;Wilson and McCormick 1997;Sponaugle et al. 2010). These features have been linked roughly with the larval stage, the transition from larval to juvenile stages or habitat transitions, and later juvenile stages where juveniles occur in nursery areas or deeper habitats (Jenkins and May 1994;Raventos and Macpherson 2001;Plaza et al. 2001;Mansur et al. 2014). ...
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... There is increasing evidence that many fish species exhibit strong prey preference and selectivity during the larval stage (Robert et al., 2008). In selective species, larvae that feed successfully on preferred prey are characterized by faster growth, which increases their probability of survival (Robert et al., 2009;Sponaugle et al., 2010;Murphy et al., 2013). Various potential consumable prey taxa occur within a given zooplankton assemblage, but in order to optimize growth and survival, larvae should preferentially feed on taxa that are abundant, easily captured, and provide the highest net gain of energy and essential nutrients (Schoener, 1971;Werner and Hall, 1974). ...
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Spatiotemporal overlap between fish larvae and their planktonic prey is an important source of recruitment variability. Over the past decade, one species of redfish, Sebastes mentella, from the Gulf of St. Lawrence (GSL) produced multiple strong cohorts following decades of low recruitment, which has generated strong interest in identifying potential drivers of larval survival. The present study provides the first detailed, multi-year assessment of larval redfish (Sebastes spp.) trophodynamics. Interannual variability in larval redfish diet composition and prey selectivity was assessed using high-resolution prey identification of larval gut contents and in situ prey fields. Eggs from the calanoid copepod Calanus finmarchicus represented the most frequently consumed prey in 3 of the 4 collection years, and contributed the largest proportion of carbon ingested by redfish larvae in all years. The high consumption of C. finmarchicus eggs by larvae, combined with evidence of positive selection for this taxon in some years, supports the hypothesis of a strong trophic link between larval redfish and a key calanoid copepod in the GSL ecosystem. Our results indicate that future efforts investigating GSL redfish recruitment processes should consider environment-driven variability in the reproductive phenology and abundance of C. finmarchicus.
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... A low nutrient concentration from clean water discharge from the dam, working interactively with a low water temperature from hypolimnetic discharge, may induce low productivity and a shortage of food availability for fish (Garnier et al. 2002;Sponaugle et al. 2010). No research had been conducted investigating impacts of dam release on primary productivity and plankton downstream the TGD. ...
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Presentation
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... Within a population, larval growth can vary spatially (e.g. Suthers et al., 1989;Sponaugle et al., 2010) and interannually (e.g. Olafsdottir and Anderson, 2010;Murphy et al., 2013;Rodríguez-Valentino et al., 2015;Takahashi et al., 2016). ...
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Monthly plankton sampling across the Straits of Florida (SOF) allowed for a thorough investigation of the feeding ecologies of four taxa of larval tunas (family Scombridae, tribe Thunnini) and the horizontal and vertical distributions of tuna larvae and their dominant prey. Before piscivory, Thunnus spp. larvae had a mixed diet of crustaceans and appendicularians, whereas skipjack tuna (Katsuwonus pelamis), little tunny (Euthynnus alletteratus), and Auxis spp. displayed highly selective and nearly exclusive feeding on appendicularians. The availability of both appendicularians and larval fish prey declined from west to east across the SOF, and appendicularians were notably patchy. In the western SOF where prey was more abundant, all taxa of tuna larvae co-occurred, indicating the sharing of resources by the larvae, in addition to the adults of these taxa using similar spawning habitat upstream in the Florida Current. In the central and eastern SOF, where prey was less abundant, only Thunnus spp. and skipjack tuna co-occurred, and these two taxa exhibited significantly different vertical distributions. Prey removal rates (estimated from gut evacuation rates and daily rations) occurring in the western SOF where tuna taxa co-occurred are likely to be sustainable by appendicularian levels within this region but would potentially not be by levels in the east. The spatial and trophic characteristics of these four abundant larval taxa highlight the potential influence of feeding-related processes on larval and adult behavior, while also illustrating a critical trophic link to the microbial food web provided by appendicularians in this oligotrophic environment.
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Scombrid fishes are considered to have adopted a survival strategy characterized by fast growth and the ability to consume large prey at an early age. Variability in feeding condition can significantly affect larval growth as early as the post first-feeding stage and may control growth-related survival during the early larval stage. Through otolith microstructure analysis, growth-selective survival was demonstrated for post first-feeding larvae of Japanese Spanish mackerel Scomberomorus niphonius, which exhibit exclusive piscivory, a high growth rate, and low tolerance to starvation. Larvae and juveniles were repeatedly collected in the Seto Inland Sea in June and July from 1997 to 1999. Growth trajectory back-calculated using otolith microanalysis was compared between the survivors (SV) captured in July and the presumed original population (OP) captured in June. Selection for fast-growing larvae was evident during the 5 d after first feeding (Days 5 to 10). More than 90% of the SV had a mean growth rate during Days 5 to 10 (G(5-10)) > 0.8 mm d(-1), and those with G5-10 < 0.8 mm. d(-1) rarely survived the period. Intensity of selection differed among 3 years. A less intense selection was observed in 1999 when the larval cohort experienced higher prey concentrations and G(5-10). Laboratory experiments demonstrated that 1 to 2 d starvation retarded the larval growth during the following larval period, and supported the conclusion that fluctuation in ichthyoplankton prey abundance alters larval survival probability by affecting the larval growth rate within a short period subsequent to first feeding.