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The Mesoamerican Barrier Reef System (MBRS) is of high ecological and economic importance to the western Caribbean region, and contains spawning sites for a number of reef fish species. Despite this, little is known of the distribution and transport of pelagic fish larvae in the area, and basic in situ information on larval fish assemblages is lacking. Here we describe the results of two biological oceanography research cruises conducted in winter‐spring of 2006 and 2007, focusing on larval fish assemblages. We use multivariate assemblage analyses to examine vertical and horizontal distribution characteristics of larval fish assemblages, to highlight key distinguishing taxa, and to relate these to the observed oceanographic structure. Our results showed a general separation between the Gulf of Honduras region, which was characterized by weaker currents and high abundances of inshore and estuarine taxa (Eleotridae, Priacanthidae), and the northern MBRS, which was subject to strong northward flow and contained a mixture of mesopelagic and reef‐associated taxa (Myctophidae, Sparidae). Although distinct patterns of vertical distribution were observed among taxa, both shallow and deep living larvae were broadly distributed throughout the study area. Analysis of historical drifter tracks highlighted the strong northward flow and low retention conditions typically present along the northern MBRS, as well as potential connectivity between the western Caribbean Sea, the Gulf of Mexico and the Atlantic Ocean.

The cryptlc and shelter-seeklng behav~our of spiny lobsters Panulirus argus Latrellle prompted the use of artlflclal shelters to examine the juvenlle population structure at Cayos-Contoy. Quintana Roo, Mexlco We tested the hypothesis that habltat type had no influence on shelter occupancy T h e arhflcial shelters used were concrete structures w~t h a PVC frame ( m m -s l z e casltas) Macrofauna a n d potential predators associated wlth the mm-casltas were also quantified The size of the lobsters harbored by these structures emphasized the Importance of the Cayos-Contoy as a nursery habltat for P argus Differences in mini-casita occupancy by luvendes and the assoclatlon between habltat and lobster size groups suggest that availab~llty of natural habitats had an influence on casita occupancy The penodlc removal ot all lobsters from the mini-casitas resulted in the vacancies being occupled mostly by a size-spec~flc group oi juveniles Trans~tional (16 to 25 m m carapace length, CL) and postalgal (26 to 35 mm CL) luvenile stages recruited malnly to vegetated habitats with larger lobsters occupylng patch reef habitats Mlni-caslta occupancy was dominated by transitional and post-algal early juvenlle stages (41 1 and 34 6% respectlvely) The fact that the highest percentage of minl-caslta occupancy is by transitional juvenlle P argusls considered to represent a 'population bottleneck effect

The Mesoamerican Barrier Reef System (MBRS) contains a diverse array of coastal habitats that are critical for the survival of the early stages of reef fish; however, the knowledge on the abundance and distribution of the early stages of coastal fishes is still limited in this region. This study investigated the species richness of larval and juvenile fishes using a combination of a sled net, standard plankton net, and a nightlight lift-net; these were deployed simultaneously at Bacalar Chico, a site on the MBRS within the protected ''Parque Nacional Arrecifes de Xcalak'' (PNAX). We collected 53 families and 118 species of larval and juvenile fishes in a small area of about 3 km 2 . This species diversity of early life-history stages is greater than previously found in surveys on the MBRS. Each gear caught a number of species exclusively, so combined sampling with the three methods provided a much fuller picture of the local larval and juvenile fish assemblage. A species-accumulation model estimated that the samples likely represented 84% of the total assemblage. Many species caught were represented predominantly by newly settled juveniles, underscoring the importance of this coastal habitat for settlement of many ecologically and economically important fish species. This information is expected to improve the conservation and management strategies in the fragile PNAX coastal zones by providing additional information based on original field data to raise awareness among managers about the ecological relevance of these coastal habitats. This study provides encouraging evidence that the PNAX is a well-suited natural protected area to preserve a critical fish habitat in a hotspot of marine biodiversity.

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