Reef fish species tend to reside over high relief habitat which makes them difficult to sample with traditional gears such as nets and trawls. Therefore, implementing and understanding the strengths and weaknesses of new approaches which incorporate acoustic and optical methods has become a priority for reef fish stock assessment. Beginning in June of 2013, a towed camera system known as the Camera-Based Assessment Survey System (C-BASS) has been used to visualize over 500 kilometers of transect and record more than 80 hours of video over several habitats in the Gulf of Mexico. Surveys have been completed on the West Florida Shelf in the Florida Middle Grounds (FMG), Madison-Swanson (MS) and Steamboat Lumps (SL) closed areas. High resolution multibeam bathymetry is available for these areas and was important for the deployment of C-BASS which is towed just above the seafloor (2-3 meters above the bottom). This system can facilitate regular surveys of fishes which inhabit untrawlable bottom types (e.g. reefs, pinnacles, boulders) and within habitats where lethal, extractive techniques are prohibited such as in protected areas. To address potential biases resulting from fish reactions towards C-BASS, observed reactive behavior was analyzed in addition to far-field reactive behavior towards C-BASS using stationary camera pods. Most fish observed on C-BASS imagery exhibited weak negative or neutral behavior at proportions of 49% and 38%, respectively. Of those fish which did negatively react to C-BASS, almost all movement was in the 180° and 0° directions (right and left) relative to the tow body's movement. Preliminary results from the direct observation (far-field) experiments also demonstrated a general lack of reactive behavior as C-BASS was towed nearby with no significant decreases in mean abundance of fishes between the periods before, during and after C-BASS was towed over an area (95% confidence level). Although behavioral reactions are species-specific, results indicate that the system may not greatly deter the species of interest (i.e. snappers, groupers, porgies, lionfish, and amberjacks) in this study. Density estimates and subsequent first-order total abundance estimates were also developed for stratified habitat types in the FMG and MS. Overall abundance estimates were greater in 2014 than in 2013 which likely were a result of increased illumination, improvements to video quality, and lower chlorophyll and turbidity levels in 2014. With minor improvements and further behavior analysis, it is expected C-BASS can provide accurate, precise abundance estimates of target reef fish species for management purposes.

This study examined the effects of the January 2010 cold spell on mangrove utilizing coral reef fishes off the southeast coast of Florida, USA, in the vicinity of Biscayne National Park (BNP). An ongoing, fishery-independent mangrove visual survey documenting fish assemblages in BNP provided data from the years 1998 to 2014 for examination. Of particular interest were the presence, abundance, and size structure for five mangrove utilizing coral reef fishes: sergeant major (Abudefduf saxatilis), yellowfin mojarra (Gerres cinereus), schoolmaster snapper (Lutjanus apodus), gray snapper (Lutjanus griseus), and great barracuda (Sphyraena barracuda). These species were selected for analysis due to their economic and ecologic importance, their potential as environmental indicators, their connectedness to multiple habitats, and their abundance within the available data set. Data were collected using a modified visual ‘belt transect’ method, consisting of 60 m2 transects running parallel to the mangrove shorelines. Data for average length of fish were reconstructed to form standard normal distributions and the resulting lengths were assigned to various age-classes to create species-specific length-frequency distributions. Variations in presence and abundance were examined across three time periods (1998-2009; 2010-2011; 2012-2014), as well as comparisons of length-frequency distributions. Following the January 2010 cold spell, the presence and abundance values for the two years immediately following the event were significantly decreased compared to the years prior to the cold spell for most of the five species at either mainland (ML) or leeward key (LK) locations. Additionally, the presence and abundance estimates typically remained statistically decreased when compared against the remaining years in the available data set. The size structures for the majority of the five species at either location, however, were not consistently significantly different between the three time periods, as was hypothesized. Instead, the analyses showed mixed results, with the size structure typically shifting towards smaller individuals immediately following the event. These findings suggest that drops in water temperature resulting from cold spells are capable of directly impacting mangrove utilizing reef fish species, albeit to varying degrees depending on various factors, such as physiological tolerances, ecological life history strategies, and habitat requirements.

No description available.

The objective of this project was to determine if the electromagnetic field (EMF) emissions from undersea power cables impacted the local and transient marine life, with an emphasis on reef fishes. The work was done at South Florida Ocean Measurement Facility of Naval Surface Warfare Center, Carderock Division, Broward County, Florida. This facility functions as the hub for a range of active undersea detection and data transmission cables. It has multiple active submarine power cables that extend several miles offshore and which can deliver power and enable data transmission to and from a range of acoustic and EMF sensors. The cables lie directly on the seabed, are buried in the sand, or are suspended in the water column. EMF emissions from a selected cable were created during SCUBA fish surveys. During the surveys the transmission of either alternating current (AC) or Direct Current (DC) was randomly intiated by the facility with no transmitted current (OFF) provided a control. The surveys were conducted using standardized transect and stationary point count methods to acquire reef fish abundances prior to and immediately after a change in transmission frequency (the divers were aware of the time of frequency change but not the specific frequencies). The divers were also tasked to note the reaction of the reef fishes to the immediate change in the EMFs emitting from the cable during a power switch. The surveys were conducted on a quarterly basis at three sampling sites offshore on the same cable. These sites were in water depths of approximately 5, 10, and 15 m, respectively and were selected based on their robust reef fish community and are representative of each of the three primary hardbottom coral reef habitats in the local offshore environment: the Inner (Shallow), Middle, and Outer (Deep) reef tracts. A total of 263 surveys were conducted: 132 transect-counts and 131 point-counts over 15 months. There were 24,473 fishes counted during transect-count surveys and with point-counts, 36,115 fishes were counted. With count types and sites combine a total of 151 species representing 35 families were recorded. An analysis of the data primarily did not find statistical differences among power states and any variables. However, this may be a Type II error as there are strong indications of a potential difference of a higher abundance of reef fishes at the sites when the power was off. There are a number of caveats to consider with this finding: the data set needs to be larger in terms of numbers of: counts, sites and eletro-sensitive species to allow for rigorous statistical analysis; also a longer time between frequency changes to allow for slower, but nonetheless important, reactions to differing EMFs might lead to differing conclusions. Obviously, more research is required to confirm the results of this study.