Abstract
Many coral reef fishes undergo ontogenetic migrations from inshore nurseries to offshore reefs. Quantifying cross-habitat connectivity is important for understanding reef fish spatio-temporal dynamics, essential habitat and spatial planning. Past studies show connectivity is mediated by distance and habitat arrangement. Few studies have documented the pathways linking juveniles and adults, nor suggested underlying orientation/navigation processes important for a more generalized understanding of ontogenetic habitat use. Ontogenetic movements of juvenile grunts, primarily Haemulon flavolineatum, in Puerto Rico were studied using mark-recapture. Small juveniles were tagged at a back-reef site designed to determine their potential movement through a series of size-specific daytime resting schools and posing a choice of direction in migration. Larger juveniles were tagged at mid-shelf reefs to capture off-reef migration to adult locations, including a proposed marine reserve. Small juveniles moved toward more exposed areas, accomplished by progressively shifting locations through existing resting schools. Movement was size-related and alongshore, but direction was primarily parallel to the coast, leading fish away from adjacent areas more directly offshore. Direction may have resulted from the potential mechanism of fish transfer between resting schools rather than by orientation cues. Larger juveniles were tracked from back-reef to fore-reef sites, but no fish were recaptured off-reef. Slower growth than predicted may have contributed to the perceived lack of movement. Localized behavior and habitat distribution appear important in determining the initial pathways of ontogenetic migration, and these may fix later directional movements to unexpected areas.
Highlights
Published: 26 February 2022Many coral reef fishes show characteristic habitat shifts during ontogeny [1–6]
This study aims to ascertain the direction taken by juvenile grunts, mainly H. flavolineatum, and the potential cues used during ontogenetic migration through a mark and recapture program
Over the 4-month period from October 2004 to January 2005, a total of 10,712 fish were sampled for recaptures (Table 2), with 1288 H. plumierii (13%) and
Summary
Many coral reef fishes show characteristic habitat shifts during ontogeny [1–6]. Such ontogenetic migrations are thought to minimize the ratio of mortality over growth [7], which has been supported empirically [3,8–10]. Ontogentic migrations are well-defined in grunts (Haemulidae) and evidenced by the shift to larger size distributions with progressive offshore locations [1,2,5,6,11]. Juvenile grunts undergo a series of migrations between habitats (and associated resting schools) [2,5,6,11,12]. These migrations are associated with changes in diet and behavior [2,10,13,14] and appear to be strongly correlated with fish length [10,15]. There are six eco-behavioral stages of development reported for Haemulon flavolineatum and
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