title: Species co-occurrence affects the trophic interactions of two juvenile reef shark species in tropical lagoon nurseries in Moorea (French Polynesia).
abstract: Food web structure is shaped by interactions within and across trophic levels. As such, understanding how the presence and absence of predators, prey, and competitors affect species foraging patterns is important for predicting the consequences of changes in species abundances, distributions, and behaviors. Here, we used plasma δ13C and δ15N values from juvenile blacktip reef sharks (Carcharhinus melanopterus) and juvenile sicklefin lemon sharks (Negaprion acutidens) to investigate how species co-occurrence affects their trophic interactions in littoral waters of Moorea, French Polynesia. Co-occurrence led to isotopic niche partitioning among sharks within nurseries, with significant increases in δ15N values among sicklefin lemon sharks, and significant decreases in δ15N among blacktip reef sharks. Niche segregation likely promotes coexistence of these two predators during early years of growth and development, but data do not suggest coexistence affects life history traits, such as body size, body condition, and ontogenetic niche shifts. Plasticity in trophic niches among juvenile blacktip reef sharks and sicklefin lemon sharks also suggests these predators are able to account for changes in community structure, resource availability, and intra-guild competition, and may fill similar functional roles in the absence of the other species, which is important as environmental change and human impacts persist in coral reef ecosystems.
authors.affiliation: Marine Sciences Program, Florida International University, 3000 NE 151st, North Miami, FL 33181, USA; Sam Houston State University, Texas Research Institute for Environmental Studies, 2424 Sam Houston Avenue, Huntsville, TX 77341, USA. Electronic address: matich.philip@gmail.com.
authors.forename: Philip
authors.initials: P
authors.lastname: Matich
authors.affiliation: Marine Sciences Program, Florida International University, 3000 NE 151st, North Miami, FL 33181, USA.
authors.forename: Jeremy J
authors.initials: JJ
authors.lastname: Kiszka
authors.affiliation: PSL Research University, EPHE-UPVD-CNRS, USR 3278 CRIOBE, CBETM, Université de Perpignan, 58 Avenue Paul Alduy, 66860 Perpignan Cedex, France; Laboratoire d'Excellence « CORAIL », France.
authors.forename: Johann
authors.initials: J
authors.lastname: Mourier
authors.affiliation: PSL Research University, EPHE-UPVD-CNRS, USR 3278 CRIOBE, CBETM, Université de Perpignan, 58 Avenue Paul Alduy, 66860 Perpignan Cedex, France; Laboratoire d'Excellence « CORAIL », France.
authors.forename: Serge
authors.initials: S
authors.lastname: Planes
authors.affiliation: Marine Sciences Program, Florida International University, 3000 NE 151st, North Miami, FL 33181, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Heithaus
mesh_terms: D000818:Animals; D057894:Coral Reefs; D017753:Ecosystem; D004784:Environmental Monitoring; D020387:Food Chain; D011114:Polynesia; D012754:Sharks / Q000502:physiology*; D014329:Tropical Climate
keywords: Coastal waters; Marine ecology; Niche separation hypothesis; Pacific; Shark nursery; Stable isotopes; Trophic shift