Michelle T. Schärer

Sound Production and Reproductive Behavior of Yellowfin Grouper, Mycteroperca venenosa (Serranidae) at a Spawning Aggregation

Reproductive behaviors and sound production of the Yellowfin grouper (Mycteroperca venenosa) are described from in-situ observations by divers as well as synchronous underwater audio-video recordings at a spawning aggregation off Mona Island, Puerto Rico. The highest abundances of M. venenosa estimated from underwater visual surveys were detected in March and April, five to nine days after the full moon (DAFM). Four distinct color phases were observed for M. venenosa; two of these were unique to the spawning aggregation and one, the white-headed phase, was exhibited during interactions with other conspecifics corresponding to courtship displays. Variations in color phases during fish interactions and group formation coupled with sounds preceded spawning, which occurred near sunset. Low-frequency (<150 Hz) sounds produced by M. venenosa were variable yet they were classified into two types, pulsed and tonal. Both types of sounds were associated with reproductive behaviors although not linked to spawning rushes. These sounds were most frequent between 1800 and 2100 h, peaked the eighth DAFM, and ceased between 11–13 DAFM. Temporal patterns in sound production suggest that peak reproduction occurred in April followed by a smaller aggregation in May of 2010. The association of passive acoustics with reproductive behaviors for M. venenosa provides a tool to help identify spawning aggregation sites and monitor spawning stock abundance to evaluate the effectiveness of management and conservation efforts for this Near Threatened grouper.

Population Structure and Phylogeography in Nassau Grouper (Epinephelus striatus), a Mass-Aggregating Marine Fish

To address patterns of genetic connectivity in a mass-aggregating marine fish, we analyzed genetic variation in mitochondrial DNA (mtDNA), microsatellites, and single nucleotide polymorphisms (SNPs) for Nassau grouper (Epinephelus striatus). We expected Nassau grouper to exhibit genetic differentiation among its subpopulations due to its reproductive behavior and retentive oceanographic conditions experienced across the Caribbean basin. All samples were genotyped for two mitochondrial markers and 9 microsatellite loci, and a subset of samples were genotyped for 4,234 SNPs. We found evidence of genetic differentiation in a Caribbean-wide study of this mass-aggregating marine fish using mtDNA (FST = 0.206, p<0.001), microsatellites (FST = 0.002, p = 0.004) and SNPs (FST = 0.002, p = 0.014), and identified three potential barriers to larval dispersal. Genetically isolated regions identified in our work mirror those seen for other invertebrate and fish species in the Caribbean basin. Oceanographic regimes in the Caribbean may largely explain patterns of genetic differentiation among Nassau grouper subpopulations. Regional patterns observed warrant standardization of fisheries management and conservation initiatives among countries within genetically isolated regions.

Distribution, Prevalence, and Genetic Analysis of Panulirus Argus Virus 1 (Pav1) from the Caribbean Sea

The pathogenic virus Panulirus argus virus 1 (PaV1) was first discovered in Caribbean spiny lobsters Panulirus argus from the Florida Keys (USA) in 1999 and has since been reported in Belize, Mexico, and Cuba; its distribution in the wider Caribbean is unknown. We collected tissue samples from adult spiny lobsters from 30 locations in 14 countries bordering the Caribbean Sea and used molecular diagnostics to assay for the presence of PaV1. PaV1 occurred primarily in the northern areas of the Caribbean, where its prevalence was highest. The virus was not found in lobsters from the southeastern Caribbean, and its prevalence was lowest in the southwestern Caribbean. DNA sequence analysis was performed on a fragment of the viral DNA to examine the genetic diversity of PaV1 on a Caribbean-wide scale. Sequence variation in the viral DNA fragment was high, with 61 unique alleles identified from 9 areas. The sharing of viral alleles in lobsters from distant locations supports the hypothesis of a strong genetic connectivity among lobsters within the Caribbean, and further supports the hypothesis that postlarvae infected with PaV1 may serve to disperse the virus over long distances.

In situ Tagging of Nassau Grouper Epinephelus striatus Using Closed-Circuit Rebreathers at a Spawning Aggregation in Puerto Rico

Acoustictelemetryisawidelyusedtechniqueemployedtobetterunderstandfish movement patterns across seascapes. Traditionally, surgical acoustic transmitter implantation is conducted at the surface, resulting in a high degree of uncertainty as to the post-release survival of the fish and the validity of the results attained from these experiments. Few studieshave conductedin situtagging, where thecapture,tagging,andreleasearecompletedentirelyatthedepthinwhichthefishoccurs naturally. Through the use of closed-circuit rebreather (CCR) technology, this study outlines the first known practical application of the methodology performed at mesophoticdepths.Insixdivesconductedatdepthsbetween40and50m,atotalof10 Nassau grouper were tagged at a spawning aggregation off the west coast of Puerto Rico. The total time (time divers arrived at the trap to time of release) for each procedure was approximately 12 min, after which all fish were released and observed without indication of stress or physiological impairment. Short-term tracking of tagged fish revealed a 100% post-surgery survival rate with maximum detection of 347 days post-surgery. Survival rates of this nature have not been quantified or reported from other tagging studies, allowing the researchers to conclude that this methodology, coupled with the efficiency provided by CCR at these depths,

Passive acoustic detection of grouper sound production

Passive acoustic recordings were used to study the behavior of red hind (Epinephelus guttatus) at spawning aggregation sites off of Puerto Rico and Mona Island, and goliath grouper (Epinephelus itajara) and red grouper (Epinephelus morio) on the West Florida Shelf. The sounds produced by each species were unique, low‐frequency pulsed sounds and associated with reproductive‐related behavior. Male red hind produced sounds composed of a series of pulses that graded into a tonal‐like sound, mostly during territorial patrolling. Long‐term acoustic recorder (LARS) data from the west coast of Puerto Rico and Mona Island showed similar diel periodicities of sound production of red hind, but had different monthly peaks in sound production. Goliath grouper sounds consisted of low‐frequency individual pulses (50‐100 Hz) that are consistent with sounds produced by a large fish, and showed lunar periodicity in sound production. Peaks in sound production occurred nightly after midnight, but sounds were also produced throughout the day. Sound production and spawning by red grouper was recorded using a remotely operated vehicle (ROV) at depths of 80‐100 m. Passive acoustic techniques can provide synoptic, long‐term time series of sound production associated with reproductive activities of soniferous species at widely spaced sites.