Abstract
The availability of suitable prey during the early life of fish may determine recruitment to the adult population. Since larval and juvenile feeding can be highly selective, their preferences for certain prey species and sizes should be considered when estimating the availability of prey. In this study, diet composition (and prey preferences) of 4984 (1366) Faroe Plateau cod (Gadus morhua) larvae and juveniles between 3 and 63 mm sampled on the central Faroe shelf (62°N, 6.8°W) over an 8-year period was investigated. Cod preyed on successively larger food items as they grew. Yolk-sac larvae consumed phytoplankton, copepod eggs and nauplii before the yolk sac was exhausted. Copepod eggs followed by calanoid nauplii were the predominant and preferred food items in the early larval stage. In the late larval stage these were replaced by small to medium sized (0.6–1.2 mm) copepod species mainly Pseudocalanus sp., Acartia sp. and early stage Calanus finmarchicus, of which the two former species appeared most preferred. Temora longicornis was highly abundant in juvenile cod, but the preference for this species was neutral. Positive selection and high abundance of late stage (≥ 1.5 mm) C. finmarchicus was observed in early juveniles, but C. finmarchicus was replaced by decapod larvae in late juveniles. Other abundant prey species such as Oithona sp. and barnacle larvae occurred in varying numbers in the guts, but were generally not positively selected at any stage. Late larval and early juvenile cod appeared to suffer from unfavourable feeding conditions as they fed on smaller prey than what they prefer potentially indicating bottle necks in the feeding at these development stages.
Highlights
Changes in fish populations are largely driven by variability in recruitment, and fluctuations in recruitment are widely believed to be determined during the early life stages
The study showed that during the pelagic period cod larvae and juveniles successively feed on copepod eggs → calanoid nauplii → copepods → malacostraca (Fig. 6), and that the shifts in diet roughly correspond to major shifts in cod development (Fig. 1)
Copepod eggs are important for early stage larvae followed by calanoid nauplii
Summary
Changes in fish populations are largely driven by variability in recruitment, and fluctuations in recruitment are widely believed to be determined during the early life stages. Recruitment may be affected by many factors during the early life stages, food availability is often considered to be a key factor affecting growth and survival of fish larvae (Hjort 1914; Anderson 1988; Cushing 1990; Leggett and Deblois 1994). Faroe Marine Research Institute, Nóatún 1, PO Box 3051, 100 Tórshavn, Faroe Islands
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
