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Diversity in coral reef fishes is not evenly distributed and tends to accumulate in the Indo-Malay-Philippines Archipelago (IMPA). The comprehension of the mechanisms that initiated this pattern is in its infancy despite its importance for the conservation of coral reefs. Considering the IMPA either as an area of overlap or a cradle of marine biodiversity, the hypotheses proposed to account for this pattern rely on extant knowledge about taxonomy and species range distribution. The recent large-scale use of standard molecular data (DNA barcoding), however, has revealed the importance of taking into account cryptic diversity when assessing tropical biodiversity. We DNA barcoded 2276 specimens belonging to 668 coral reef fish species through a collaborative effort conducted concomitantly in both Indian and Pacific oceans to appraise the importance of cryptic diversity in species with an Indo-Pacific distribution range. Of the 141 species sampled on each side of the IMPA, 62 presented no spatial structure whereas 67 exhibited divergent lineages on each side of the IMPA with K2P distances ranging between 1% and 12%, and 12 presented several lineages with K2P distances ranging between 3% and 22%. Thus, from this initial pool of 141 nominal species with Indo-Pacific distribution, 79 dissolved into 165 biological units among which 162 were found in a single ocean. This result is consistent with the view that the IMPA accumulates diversity as a consequence of its geological history, its location on the junction between the two main tropical oceans and the presence of a land bridge during glacial times in the IMPA that fostered allopatric divergence and secondary contacts between the Indian and Pacific oceans.

Whale sharks, Rhincodon typus, are often perceived as solitary behemoths that live and feed in the open ocean. To the contrary, evidence is accumulating that they are gregarious and form seasonal aggregations in some coastal waters. One such aggregation occurs annually north of Cabo Catoche, off Isla Holbox on the Yucatán Peninsula of Mexico. Here we report a second, much denser aggregation of whale sharks (dubbed \"the Afuera\") that occurs east of the tip of the Yucatán Peninsula in the Caribbean Sea. The 2009 Afuera event comprised the largest aggregation of whale sharks ever reported, with up to 420 whale sharks observed in a single aerial survey, all gathered in an elliptical patch of ocean approximately 18 km(2). Plankton studies indicated that the sharks were feeding on dense homogenous patches of fish eggs, which DNA barcoding analysis identified as belonging to little tunny, Euthynnus alletteratus. This contrasts with the annual Cabo Catoche aggregation nearby, where prey consists mostly of copepods and sergestid shrimp. Increased sightings at the Afuera coincide with decreased sightings at Cabo Catoche, and both groups have the same sex ratio, implying that the same animals are likely involved in both aggregations; tagging data support this idea. With two whale shark aggregation areas, high coastal productivity and a previously-unknown scombrid spawning ground, the northeastern Yucatán marine region is a critical habitat that deserves more concerted conservation efforts.

Length-weight ( LWR ), length-length ( LLR ) relationships and relative condition factor ( K n ) were determined for the conchfish Astrapogon stellatus (Cope, 1867) in the Mesoamerican Reef System, Mexico. A total of 26 specimens were collected between 2016 and 2018. The LWR for A. stellatus was W = 0.0159* TL 2.972 . LLR was highly significant ( r 2 = 0.989) and the range of K n was 0.85–1.26. These findings have not been previously reported in the literature, such data is valuable for understanding population dynamics for this a poorly known species that could be within some endangered category.

Examination of the mantle cavity of 310 penshells Pinna carnea , collected from seagrass beds in southwestern Dominican Republic, revealed the presence of four species from three phyla as potential symbionts. The shrimp Pontonia sp. was found in 178 penshells, the cardinalfish Astrapogon stellatus in 18, an anemone (order Actiniaria) in two, and a pea crab (family Pinnotheridae) in one. The penshell likely provides these organisms with a refuge from predators. It also provides nutrition for shrimp as they consumed food trapped in the mucus secreted by the penshell host. All of the cardinalfish, and 91% of the shrimp, were found in penshells measuring >150 mm in hinge length. At approximately 150 mm, the shells of P. carnea thicken and so flatten less when the valves are closed. As a result, larger penshells provide more mantle-cavity space for accommodating organisms. Shrimp and cardinalfish size increased with the size of the host penshell. The positive relationship between shrimp size and penshell size, a prevalence of male-female pairs of shrimp and other field observations, suggest that a long-term association exists between shrimp and penshells, and that the mating system of the shrimp involves social monogamy.

Spatial and temporal patterns of larval replenishment to the San Blas Archipelago were measured using 3 light traps in each of 3 habitats (exposed, lagoon and back-reef) over 18 lunar months from December 1996 to June 1998. Traps were sampled for 19 consecutive nights centred on the new moon in each month. The effects of environmental variables (wind speed and wind direction, tidal range, rainfall, solar radiation and water temperature) on catches were examined both in the days immediately prior to settlement and during the entire larval phase using 2 approaches. Firstly, time-series analyses were used to compare night-to-night patterns in light trap catches of 11 species (Astrapogon puncticulatus, Eucinostomus melanopterus, Lutjanus apodus, L. mahogani, Ophioblennius atlanticus, Stegastes dorsopunicans, S. partitus, S. planifronsSynodontidae spp.,Thalassoma bifasciatumand an unidentified blenny) with environmental variables. Secondly, modified correlation analysis was used to examine the relationships between environmental variables, averaged over larval durations, and light trap catches of 6 of these species. Time-series analysis detected significant correlations between catches of 8 species and wind direction; however, correlations were often weak and variable in direction. Similarly, there were weak correlations between day-to-day catches of all but 3 species and water temperature. Modified correlation analysis also found that water temperature was correlated with catches of 4 species (Lutjanus mahogani, Stegastes dorsopunicans, S. partitusandS. planifrons). Catches of the remaining species,Ophioblennius atlanticusandThalassoma bifasciatum, were not correlated with environmental variables in these analyses. Multiple-regression analysis could not detect any combined effects of environmental variables on patterns of light trap catches, although this analysis also identified weak correlations (R² = 0.08 to 0.29) between catches ofLutjanus mahogani, Ophioblennius atlanticus, Stegastes dorsopunicans, S. partitus, S. planifronsandThalassoma bifasciatumand water temperature.