Abstract. --- Specimens of the four study species were collected during cruises to outer-continental shelf reefs of the northeastern Gulf of Mexico. Age was estimated for all serranid species using whole otoliths and C. enchrysurus ages were determined from transverse sections of sagittal otoliths. Ring structure observed on otoliths was validated as having an annual periodicity for P. martinicensis using marginal increment analysis. Ring structure on remaining species was assumed to correspond to age (years). Pronotogrammus martinicensis, H. vivanus, S. phoebe, and C. enchrysurus exhibited maximum ages of 9, 8, 5, and 11, respectively.  Spatial variations in size-at-age were observed in P. martinicensis populations.  Individuals inhabiting reefs in the Madison-Swanson Reserve area on the West Florida Shelf edge exhibited the fastest growth rates, while the slowest growing P. martinicensis were collected from the Alabama Alps Reef, the farthest west study reef.

         Pronotogrammus martinicensis and H. vivanus are both protogynous hermaphrodites.  Evidence of active spawning was observed in the months from February through July for P. martinicensis, and March and May for H. vivanus.  Serranus phoebe was observed to be a simultaneous hermaphroditic capable of spawning year-round.  Batch fecundity estimates for P. martinicensis ranged from 149-394 oocytes per fish.

         Size selectivity was evident in our primary sampling method, hook and line using small tandem bait hooks. Smaller size-classes of all species examined were under-represented in our samples, hindering accurate growth modeling.  Due to the protogynous nature of P. martinicensis and H. vivanus, hook and line sampling also tended to select for males. Future descriptions of the reproductive biology of both protogynous species would be more complete if less selective sampling methods could be successfully employed.

         The data presented here contribute to a better assessment of the fish community of the northeastern Gulf of Mexico. Little information on age and reproduction was previously available for the serranid and pomacentrid species investigated in the present study.  These species are important links between both planktonic or benthic food resources and economically-valuable groupers, snappers, and amberjacks.  If a catastrophic natural or anthropogenic event occurred in these outer continental shelf reef habitats, the resultant loss of these forage species would immediately impact regional fish production via the food chain.  This would be particularly true for reef-resident commercial and recreational fish species that depend extensively upon a diet of small forage fish species.  Recovery to a stable community, fully repopulated with small forage fish species, would require at least a decade, possibly longer if the habitat had been substantially degraded during the initial disturbance.

Introduction

         Over the period of 1997-2002, the U.S. Geological Survey (USGS) undertook a program of investigations to develop knowledge of outer continental shelf (OCS) fish community structure. This program of investigations was conducted by the Coastal Ecology and Conservation (CEC) Research Group, Center for Aquatic Resource Studies, Florida Integrated Science Center, Gainesville, Florida under the auspices of the USGS Outer Continental Shelf Studies Office. This research program responded to the living resource information needs of the Minerals Management Service (MMS) in relation to its ecological stewardship role on the OCS. Investigations conducted by USGS from 1997-1999 emphasized knowledge of sensitive hard-bottom and deep reef ecosystems in areas of hydrocarbon exploration and development. Beginning in 2000, the USGS CEC Research Group began placing increased emphasis on integrated oceanographic and comparative biological studies of total ecosystem structure and function.  Additional research partners with abiding specialized expertise in this regard were solicited to address specific topics requiring a broad oceanographic perspective, or a pre-existing extended time-series of sampling data.

         The outer-continental shelf reefs of the NEGOM are home to many large and well-known species, particularly seabasses [i.e., groupers (Serranidae), amberjacks (Carangidae), and snappers (Lutjanidae)]. However, lesser-known small serranids and species of several other families are numerically dominant on NEGOM deep-reef biotopes (Weaver et al 2002). Of the small serranids inhabiting NEGOM shelf-edge deep reefs (60-120 m), two anthiine planktivores, the roughtongue bass, Pronotogrammus martinicensis (Guichenot 1868) (Plate I), and the red barbier, Hemanthias vivanus (Jordan and Swain 1885) (Plate I), are dominant (Koenig et al. 2000; Weaver et al. 2002).  A third serranid, the tattler, Serranus phoebe (Poey 1852), and a damselfish (Pomacentridae), the yellowtail reef-fish, Chromis enchrysurus, (Jordan and Gilbert 1882) are also abundant on NEGOM OCS reefs (Koenig et al. 2000, Weaver et al. 2002).  Together, these four species are of great ecological importance to the deep reef ecosystem, consuming much of the available biomass of plankton and small mobile epibenthos, and in turn forming a substantial portion of the forage base of larger piscivores.

         Pronotogrammus martinicensis, H. vivanus, and C. enchrysurus feed mostly on small zooplankton such as copepods and amphipods (Bullock and Smith 1991, Weaver et al. 2002). In contrast, S. phoebe feeds on a variety of small epibenthic crustaceans and small fishes (Bullock and Smith 1991, Robins and Starck 1961, Weaver et al. 2002).

         All four species are important prey items for larger reef and pelagic predators. Stomach content analyses have revealed that P. martinicensis and H. vivanus are preyed upon by commercially important species, including red snapper (Lutjanus campechanus) and grouper (Mycteroperca spp. and Epinephelus spp.) (Bullock and Smith 1991, Weaver et al. 2002). In addition to their ecological importance, P. martinicensis, H. vivanus, and other small deep-reef species are collected by a small but profitable deep-water marine ornamental fishery. These fish are brightly colored (Plate I) and extremely difficult to collect alive, making them valuable to many aquarists.  Individual specimens may sell for more than $100 each in the overseas aquarium market (Chris Cole, Chris's Marine, LLC, personal communication; Forrest Young, Dynasty Marine Associates, personal communication).

         Knowledge of the life history of these forage species is not only crucial to ensuring healthy populations of the individual prey species, but is also important to the multi-species management of the larger, more economically-important fishery species (e.g., groupers, snappers, amberjacks).  Currently, most fisheries are managed from a single-species approach based solely on abundance and age/size structure. Trophic interactions and fluctuations in prey density are not included in management analyses. However, recent studies indicate a multi-species approach may better explain population dynamics and spatial shifts in abundance (Read and Brownstein 2003).  For example, when herring stocks in the Gulf of Maine collapsed during the 1970's, humpback whale numbers also diminished locally as these predators relocated to areas of higher prey abundance (Payne et al. 1990, Weinrich et al. 1997). Some reef-associated predators, however, may exhibit little emigration from their home reefs (Collins et al. 1996) making them less likely to relocate in the event of prey shortage. As a result, knowledge of the biology of prey populations such as P. martinicensis, H. vivanus, and S. phoebe, as well as the factors influencing abundance and distribution of these species, is useful to the successful management of the larger predators.

         Despite the ecological and economic importance of small serranid forage species, comprehensive information concerning their life history remains scarce. Individuals of P. martinicensis and H. vivanus begin their life as a female, then change into a male at the onset of some biological or sociological cue (Coleman 1981, Hastings 1981). This sequence of sexual change is termed protogynous hermaphrodism. Serranus phoebe has been identified as a simultaneous hermaphrodite, with gonads containing simultaneously active male and female gonad tissue (Smith 1959).  In each of these three species, however, a detailed description of reproductive biology has not been generated. Neither has the age-structure or size-structure for any of these species been described. In the present study, we report on these aspects of life history (age and reproduction) for P. martinicensis, S. phoebe, and H. vivanus.  Data for the fourth study species, C. enchrysurus, are limited, but sufficient to provide a preliminary report on longevity at this time.  New life history information for these ecologically key species is discussed in relation to the roles these species play in the NEGOM deep-reef ecosystem.

         The present investigation is the result of Florida Marine Research Institute (FMRI) collaboration with the USGS in holistic research on fish communities on the OCS in the Northeastern Gulf of Mexico (NEGOM). The St. Petersburg Laboratory of the FMRI has contributed its special expertise in terms of a long-standing program of life history research on resource and forage fish species of the Gulf of Mexico (GOM).  Support to the FMRI from the USGS OCS Ecosystem Studies Program enabled particular attention to determination of key life history parameters (age and reproduction) of three small, highly-abundant fishes of OCS deep reefs.  These fishes form a substantial portion of the forage base of economically important resource species, including snappers and groupers. Thus, knowledge of their longevity, age structure, and age at first reproduction is critically important to understanding the ecology, productivity, and repopulation potential of the food base of deep reef ecosystems in the NEGOM.  This knowledge may prove valuable in assessing current and future anthropogenic impacts upon deep reef ecosystems due to harvest of both forage base species and their larger predators, and/or due to habitat disturbance from hydrocarbon exploration and development, or other human enterprises.