Feeding ecology of American sand lance Ammodytes americanus larvae from Long Island Sound

Abstract

Sand lance larvae consumed phytoplankton and various developmental stages of the copepods Ternora longicornis, Acartia hudsonica and Pseudocalanus sp. Their diet changed with ontogeny: small larvae consumed phytoplankton and larger larvae ate copepods of increasingly older developmental stages. Samples taken during daylight indicated that the larvae have a gut capacity of approximately 0.56 % of their body dry weight. Laboratory studles conducted with live larvae indicated non-selective feeding on copepod n a u p h , but in the field, Ivlev indlces indicated selection for T 1ong1corni.s nauplii and against A. hudsonjca n a u p h . Larger larvae selected for T longicornjs copepodites and against A. hudsonica copepodites and females, but as they approach metan~orphosis, they began to select for A. hudsonica females. The feeding behavior of small larvae is passive, but becomes more aggressive as the larvae mature. Biomass consumed Increased with Increased prey density and water temperature. Clearance rates for larvae at 7OC In the laboratory were 0.02, 0.05, 0.48 and 3.2 1 d' for 4.5 to 5.0, 6 to 7.0, 10 to 11.0, and 21 mm ldrvae, respectively. Calculations of the predatory impact of sand lance larvae on copepod nauplii ind~calu that they are lnslgnificant consumers taking a maximum of 13.4 % of the copepod production per ddy.