Food web constraints on larval growth in subtropical coral reef and pelagic fishes

• Published in: Marine ecology. Progress series (Halstenbek) 2020-09, Vol.650, p.19-36
• Main Authors: Gleiber, Miram R., Sponaugle, Su, Robinson, Kelly L., Cowen, Robert K.
• Format: Article
• Language: English
• Subjects: Additives; Aquatic crustaceans; Coral reefs; Density; Environmental effects; Fish; Food chains; Food webs; Growth rate; Interspecific relationships; Katsuwonus pelamis; Larvae; Larval development; Measuring instruments; Pelagic fish; Plankton; Predation; Predator-prey interactions; Predators; Prey; Sampling; Sampling methods; Subtropical zones; Survival; Taxa; Temperature effects; THEME SECTION: Latest advances in research on fish early life stages
• ISSN: 0171-8630; 1616-1599
• DOI: 10.3354/meps13217

Prey availability and predation pressure are thought to be key constraints on larval growth, especially in low-productivity, subtropical environments. Yet, measuring their effects on larval fishes has been challenging, given the dynamic biophysical drivers of plankton distributions and small scales of interactions. We integrated fine-scale net tows (10s of meters) with in situ imaging to explore how predator–prey interactions influence larval fish growth in the Straits of Florida. Otolith-derived recent growth was analyzed for 3 ecologically important fishes: 2 coral reef labrids (Thalassoma bifasciatum and Xyrichtys novacula) and 1 tuna (Katsuwonus pelamis), with differing mean growth rates (labrids 0.25 mm d−1, K. pelamis 0.44 mm d−1) and prey (labrids–copepods; tuna–appendicularians). We used generalized additive models to examine the interactive effect of background density and frequency of elevated (>2 SD above background) prey and predators on recent (last 3 d) larval growth. For all taxa, recent growth increased with prey background density. Recent growth of labrids was also higher when copepod densities were more often elevated (14% of transect >20 ind. m−3) above otherwise low background densities (2 ind. m−3). Predators (chaetognaths and hydromedusae) had a growth-selective effect: stronger selection in transects with high-density predator patches, although the direction of the effect was species-specific. The effect of temperature was taxa-specific: growth increased with temperature for the labrids and peaked at an optimum (28°C) for the rapidly growing tuna. Integration of these fine-scale sampling methods improves our understanding of the variable influence of prey and predators on larval growth and, consequently, larval survival.