Michael Nemeth

Recent Region-wide Declines in Caribbean Reef Fish Abundance

Profound ecological changes are occurring on coral reefs throughout the tropics, with marked coral cover losses and concomitant algal increases, particularly in the Caribbean region. Historical declines in the abundance of large Caribbean reef fishes likely reflect centuries of overexploitation. However, effects of drastic recent degradation of reef habitats on reef fish assemblages have yet to be established. By using meta-analysis, we analyzed time series of reef fish density obtained from 48 studies that include 318 reefs across the Caribbean and span the time period 1955-2007. Our analyses show that overall reef fish density has been declining significantly for more than a decade, at rates that are consistent across all subregions of the Caribbean basin (2.7% to 6.0% loss per year) and in three of six trophic groups. Changes in fish density over the past half-century are modest relative to concurrent changes in benthic cover on Caribbean reefs. However, the recent significant decline in overall fish abundance and its consistency across several trophic groups and among both fished and nonfished species indicate that Caribbean fishes have begun to respond negatively to habitat degradation.

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.

The Distribution of Herbivorous Coral Reef Fishes within Fore-reef Habitats: the Role of Depth, Light and Rugosity

Abstract. Examining the relationship between habitat characteristics and utilization patterns by herbivorous fishes on coral reefs will add to our understanding of the factors that influence the abundance and distribution of this important group. The abundances of parrotfishes (Scaridae) and surgeonfishes (Acanthuridae) on fore-reef habitats were sampled along an inshore-offshore gradient to provide for within reef and cross-shelf comparisons in relation to the environmental parameters of depth and topographic relief. Temporally replicated visual surveys were conducted along permanent belt transects (100m2) at three depth intervals (3, 10, 15 m) to obtain data on fish species density and lengths, which were used to calculate biomass. The roving herbivorous fish assemblage was dominated by three species of parrotfishes (Scarus iseri, Sparisoma aurofrenatum and S. viride) and three surgeonfishes (Acanthurus bahianus, A. chirurgus and A. coerulus). Overall the biomass of both families was highest at 3m compared to 10 or 15m (p<0.05). However, the relative decrease in biomass across depths for both families was greatest at inshore reefs where water transparency is lowest. The mean biomass for both families differed between inner and mid-shelf reefs at 10 and 15 m (p<0.05) but not at 3m. Fish biomass was correlated to reef topographic relief at 3m for parrotfishes (p<0.05) and at all three depth intervals for surgeonfishes (p<0.05). Overall patterns of herbivore biomass across the shelf reflect differences in light penetration, suggesting that fish may be responding to algal productivity. Thus, within fore-reef habitats along a cross-shelf gradient water transparency and topographic relief may interact to structure biomass patterns.

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,

Marine Managed Areas and Associated Fisheries in the US Caribbean

The marine managed areas (MMAs) of the U.S. Caribbean are summarized and specific data-rich cases are examined to determine their impact upon fisheries management in the region. In this region, the productivity and connectivity of benthic habitats such as mangroves, seagrass and coral reefs is essential for many species targeted by fisheries. A minority of the 39 MMAs covering over 4000km(2) serve any detectable management or conservation function due to deficiencies in the design, objectives, compliance or enforcement. Fifty percent of the area within MMA boundaries had no-take regulations in the U.S. Virgin Islands, while Puerto Rico only had 3%. Six case studies are compared and contrasted to better understand the potential of these MMAs for fisheries management. Signs of success were associated with including sufficient areas of essential fish habitat (nursery, spawning and migration corridors), year-round no-take regulations, enforcement and isolation. These criteria have been identified as important in the conservation of marine resources, but little has been done to modify the way MMAs are designated and implemented in the region. Site-specific monitoring to measure the effects of these MMAs is needed to demonstrate the benefits to fisheries and gain local support for a greater use as a fisheries management tool.

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.