Gray's Reef Fish Monitoring Likely places of aggregation for local recreation and commercial fish species include the 'hard bottom,' limestone outcroppings which sporadically interrupt the sandy sea floor found off the coast of Georgia. "Georgia lacks a program to monitor overall fish assemblages on a seasonal and annual basis to detect relative changes in species abundance and composition," according to Lt. Dave Score, Assistant Manager at Gray's Reef National Marine Sanctuary and coordinator of a pilot fish monitoring study. "In general, few underwater studies have been performed on hard bottom reefs due to the wide and discontinuous distribution of these habitats, deep depths, and limited visibility." Gray's Reef National Marine Sanctuary is in its second year of a new reef fish monitoring program. The program monitors reef fish to 1) identify species abundance and diversity, 2) determine relative changes and annual stability of reef fish assemblages, 3) identify seasonal characteristics and trends, 4) establish methods for long term sampling, and 5) build baseline data for future and historical comparisons. The Gray's Reef reef fish monitoring program is a seasonal fish census performed at 32 locations along a representative ledge community located within the sanctuary. For the first year of the study 3 different monitoring methods have been employed to assess the best technique with which to continue the long term monitoring program. Many of the methods previously developed for fish censusing utilized surface deployment techniques (i.e. trawls and traps.) The few studies utilizing in situ or underwater methods were created for shallow coral reefs found in areas of high visibility, conditions rarely encountered off the coast of Georgia. In order to create a successful monitoring and sampling program for an isolated reef found 60 feet underwater, methods must be tested for applicability and accuracy. The three methods utilized in the reef fish monitoring program include point counts, diver transects, and video transects. To obtain a point count, fish located within an imaginary cylinder radiating 5 meters from a scuba diver are identified and counted. The diver transect method is accomplished with a scuba diver swimming along a permanent line or transect located on the hard bottom reef. Similarly, the video transect method is performed with a diver swimming the same transect line, but instead of visually identifying the animals, video footage is captured for later analysis. Preliminary results indicate that fish are more prevalent and diverse in the Fall rather than the Spring at Gray's Reef. Exceptions included the longspine porgy, the cowfish, and the gag grouper, all of which occurred in larger numbers in Spring than Fall. Species found only in the Spring season included the leopard toadfish, the red porgy, and the checkered blenny. Of the species found during both seasons at Gray's Reef, only five species were found to occur in similar densities in both the Spring and the Fall. These include the red goatfish, slippery dick, spottail pinfish, belted sand fish, and the black sea bass. Results comparing the three methods indicate that the point count method identifies almost twice as many species and over three times as many individuals over an equal area. For example, the point count method censused a total of 11, 097 individuals from 45 different species at Gray's Reef in the fall of 1995 while over a similar area the transect method measured only 3, 613 individuals from 25 different species. Lt. Score suggests that the variability in values between the two methods is a result of the longer time needed to perform the point counts, allowing the observer to more accurately record the number of individuals present. Although the point count method provides more data, there is inherent variation between observers. The analysis of the first year data set will quantify the significance of the observer variation as well as the significance of observed changes in species abundance during subsequent seasons and years. The year long effort has proven valuable in comparing diver sampling techniques. Score added, "just as not all bait is good for catching every fish, no one technique effectively samples all fish species." Gray's Reef will continue fish monitoring efforts using a combination of the techniques. Point counts will be used to sample cryptic, secretive, and grazing mid-water species; visual transects will be used to sample predators such as grouper and porgy; and video transects will be performed to provide an overall picture of reef condition for historical comparison. Individual fish studies are also being performed on a year-round inhabitant of Gray's Reef, the Black Sea Bass. Since 1995, Gray's Reef has been collaborating with South Carolina Marine Resources on a tag and recapture initiative to study the distribution, relative abundance, and critical habitat of this economical and ecologically important fish species. According to Reed Bohne, Director of Gray's Reef National Marine Sanctuary, "monitoring is vital to sanctuary management. It allows us to identify trends of reef fish populations over time while helping us to understand associations of fish populations with live bottom habitat." "By distinguishing between natural variation in populations and the variations caused by human activities we will be able to gain a better understanding of the balance between nature's impact and human use of the natural resource. Snap shot studies involve too much variability to separate population responses to nature verses human impact. So the only way to do that is through long term monitoring." top