Investigating the use of underwater video for the determination of size, stock density, and temporal patterns of habitat usage of grouper on hard-bottom habitats Project Number 08-FEG-12 Erin J. Burge1, Jim Atack2, Craig Andrews3 Report Date: 10 November 2009 1Corresponding author. Coastal Carolina University, Department of Marine Science, PO Box 261954, Conway, SC 29526, phone: (843) 349-6491, e-mail: [email protected] 2In Sea State Inc., 111 SW 20th St., Oak Island, NC 28465 3Over & Under Adventures Inc., 4956 Longbeach Rd # 14-149 Southport, NC 28461 Final Report 08-FEG-12 ABSTRACT Accurate assessments of economically and ecologically important finfish populations are critical to single- and multi-species fishery management. As such, a diversity of data collection methodologies are advantageous for species of high economic value, both from a scientific desire to ensure the most sound population assessments, and from the perspective of public acceptance of scientific and management recommendations for the use of fishery resources. In this pilot project we investigated the use of a non-traditional and relatively inexpensive, collaborative method for enhancing fishery-independent datasets by collecting underwater video of grouper habitats. To our knowledge, a stationary video supplemental stock assessment for gag grouper (Mycteroperca microlepis) has not previously been attempted. Underwater video techniques were used to document the presence/absence, estimated size, density, behavioral patterns, and temporal habitat usage of gag grouper on shallow water, hard-bottom habitats on the continental shelf of North Carolina. A comparison between video findings and diver visual surveys of groupers at the same locations was also made. Survey dives (n = 57) were conducted from June 2008 – January 2009 and resulted in observations of 1813 scamp (M. phenax), 305 gag, 97 yellowmouth grouper (M. interstitialis) and 118 individuals of other serranid species in the total standard definition (SD) video footage analyzed (24.6 h). Comparing equal segments of each video (15 minute) resulted in observations of 760 scamp, 115 gag, 33 yellowmouth, 27 graysby (Cephalopholis cruentatus), 13 red grouper (Epinephelus morio), nine rock hind (E. adscensionis), two goliath grouper (E. itajara), and six unidentified serranids in 8.5 hours of video observation. Comparisons were made at multiple locations, using baited and unbaited camera deployments on ledge and live-bottom habitats. There were no significant differences in the numbers of gag and scamp detected for surveys in which bait was not used, nor were differences detected for scamp between the two habitat types. Gag grouper were more frequently observed on live-bottom habitats. With the necessity of accurate assessments for resource managers becoming more important, non-extractive survey techniques, similar to those employed in this program, should be considered for future applications. These video survey techniques were also valuable for observations of fish community structure and some behavioral traits, suggesting that the addition of similar video observation protocols to MARMAP (or similar) fishery-independent data collections would be very valuable for immediate assessments on critical species, and for long- term monitoring of trends in community structure. 2 INTRODUCTION Accurate assessments of economically and ecologically important finfish populations are critical to single- and multi-species fishery management. As such, a diversity of data collection methodologies are advantageous for species of high economic value, both from a scientific desire to ensure the most sound population assessments, and from the perspective of public acceptance of scientific and management recommendations for the use of fishery resources. The latest gag grouper assessment and recommendations (SEDAR10, 2006) utilized data from both fishery- dependent and fishery-independent indices of abundance. These fishery-dependent datasets included commercial handline and longline fisheries, recreational headboat landings and MRFSS data from the recreational charter and private boat sectors. Fishery-independent data were developed from the SEAMAP reef fish video survey in the Gulf of Mexico and MARMAP cruises in North and South Carolina. Groupers (Family Serranidae, Subfamily Epinephilinae) play an important global role in hard-bottom ecosystems as high trophic level predators, and also support valuable commercial and recreational fisheries (Parrish, 1987). Groupers primarily live in habitats of complex topography and hard substrates (Chiappone et al., 2000; Smith, 1961) over a range of depths (1 to 300 m), and eat mainly fishes and crustaceans (Parrish, 1987). Certain characteristics of moderate to large species within the group that potentially negatively affect fisheries include slow growth, delayed reproduction, long life span, reduced spawning period, and commonly, protogynous sex reversal (reviewed in Coleman et al., 2000). Along the continental shelf of North Carolina gag and scamp grouper were the most commonly recorded moderate to large serranids from hard-bottom visual diver surveys in the 1970s (1975-80) and the early 1990s (1990-92) (Parker Jr. and Dixon, 1998), although they share space with other members of the snapper-grouper complex in this region (Grimes et al., 1982; Parker Jr., 1990; Quattrini and Ross, 2006; Quattrini et al., 2004). Both gag and scamp display reproductive aggregation behavior (Coleman et al., 1996) and appear to have limited home ranges (Heinisch and Fable Jr., 1999; Kiel, 2004). Kiel (2004) reported a tendency of gag to be site specific and to utilize a central core site as a result of numerous relocations of tagged gag on or near specific patch reefs. In this project we investigated the use of non-traditional and relatively inexpensive, collaborative methods for enhancing fishery-independent datasets by collecting underwater video data of gag grouper habitats without fish extraction. Underwater video techniques are useful for quantifying and observing fishes and were used in this study to estimate grouper sizes, densities, behavior, and temporal patterns of habitat usage on hard-bottom habitats near Cape Fear, North Carolina. Numerous previous studies have examined the use and efficacy of underwater video techniques (e. g.: Cappo et al., 2004; Gledhill et al., 1996; Harvey et al., 2007; Harvey et al., 2003; Pfister and Goulet, 1999). Underwater video techniques are practical because the recordings are a less intrusive, non-extractive method of data collection that reduces diver affects and observer bias that can arise with other collection methods (reviewed in Harvey et al., 2004). Video recordings are also valuable because they represent data on a permanent record that allows the opportunity to measure more variables from a given data set (Cappo et al., 2007) and to revisit historical data. The collection of video data also, to a large degree, removes the need for field deployment of scientific specialists, and provides an exciting “product” for use in communicating science to stakeholders and the general public (see attached video summary). Final Report 08-FEG-12 The biology and behavior of fish species of interest are important for determining the underwater video techniques most appropriate for the survey methodology (Willis et al., 2000). This is especially true for baited underwater video techniques which are needed to offset biases introduced by changes in fish behavior (Willis et al., 2000). Baited video observation has been successfully used to document large, mobile species, including members of the snapper-grouper complex (Langlois, 2006; Rand et al., 2006) in the past. In contrast, Posey and Ambrose (1994) found that non-baited cameras may be less intrusive than baited camera systems since the absence of bait ensures that there will be no effective change in fish behavior regarding feeding. There are trade-offs to using non-baited video techniques including greater field time and more expensive equipment to ensure that statistically testable data is collected (Posey and Ambrose, 1994). This pilot project was designed to use underwater video data collection to document the presence/absence, estimated size, density, and temporal habitat usage of gag grouper (Mycteroperca microlepis) on shallow water, hard-bottom habitats on the continental shelf of North Carolina, and to compare the video findings to diver visual surveys of groupers at the same locations. Additional information was collected on other species of observed groupers, including primarily scamp (M. phenax) and yellowmouth grouper (M. interstitialis). Recent stock assessments for the Atlantic gag grouper indicated that the species is experiencing overfishing and noted that there is lack of fishery-independent abundance data for southern North Atlantic gag (SEDAR10 Review Workshop, 2007), indicating a need for additional monitoring of this species for future stock assessments and management recommendations. MATERIALS AND METHODS Study sites Video locations were chosen from a private database of known hard-bottom locations (J. Atack and C. Andrews, personal communication) and also included established MARMAP sampling sites in the depth range of 23 – 35 m (Figure 1). Sampling sites included previously visited and unvisited locations by the study authors. Factors used to select sites for each field day included recent local conditions, such as prevailing wind and wave forecasts, recent reports of bottom visibility,