Site Characterization for Biscayne National Park: Assessment of Fisheries Resources and Habitats
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NOAA Technical Memorandum NMFS-SEFSC-468 Site Characterization for Biscayne National Park: Assessment of Fisheries Resources and Habitats Jerald S. Ault, Steven G. Smith, Geoffrey A. Meester, Jiangang Luo, and James A. Bohnsack U.S. Department of Commerce National Oceanic and Atmospheric Administration National Marine Fisheries Service Southeast Fisheries Science Center 75 Virginia Beach Drive Miami, Florida 33149 October 2001 NOAA Technical Memorandum NMFS-SEFSC-468 Site Characterization for Biscayne National Park: Assessment of Fisheries Resources and Habitats Jerald S. Ault 1, Steven G. Smith 1, Geoffrey A. Meester 1, Jiangang Luo 1, and James A. Bohnsack 2 U.S. DEPARTMENT OF COMMERCE Donald L. Evans, Secretary National Oceanic and Atmospheric Administration Scott B. Gudes, Acting Under Secretary for Oceans and Atmosphere National Marine Fisheries Service William T. Hogarth, Assistant Administrator for Fisheries October 2001 This technical memorandum series is used for documentation and timely communication of preliminary results, interim reports, or special purpose information. Although the memoranda are not subject to complete formal review, editorial control, or detailed editing, they are expected to reflect sound professional work. 1 University of Miami, Rosenstiel School of Marine and Atmospheric Sciences, Miami, FL 2 NOAA/NMFS Southeast Fisheries Science Center, Miami, FL NOTICE The National Marine Fisheries Service (NMFS) does not approve, recommend, or endorse any proprietary product or material mentioned in this publication. No reference shall be made to the NMFS, or to this publication furnished by NMFS, in any advertising or sales promotion which would indicate or imply that NMFS approves, recommends, or endorses any proprietary product or proprietary material mentioned herein or which has as its purpose any intent to cause directly or indirectly the advertised product to be used or purchased because of NMFS publication. This report should be cited as follows: Ault, J.S., S.G. Smith, G.A. Meester, J Juo, and J.A. Bohnsack. 2001. Site Characterization for Biscayne National Park: Assessment of Fisheries Resources and Habitats. NOAA Technical Memorandum NMFS-SEFSC-468. 156 pp. This report will be posted on the NMFS Southeast Fisheries Science Center website at URL – http://www.sefsc.noaa.gov/ Copies may be obtained by writing: National Marine Fisheries Service Southeast Fisheries Science Center 75 Virginia Beach Drive Miami, Florida 33149 or National Technical Information Service 5258 Port Royal Road Springfield, Virginia 22161 (800) 553-6847 or (703) 605-6000 <http://www.ntis.gov/numbers.htm> ii Executive Summary Biscayne National Park (BNP) in southeastern Florida is a unique tropical marine environment of national significance, renown for its productive coral reef ecosystem, diverse natural resources, important fishing opportunities, and spectacular scenic beauty. BNP’s coastal bay and coral reef habitats play a critical role in the function and dynamics of the larger Florida Keys coral reef ecosystem and contribute substantially to the multibillion dollar tourism and fishing industry. Park waters provide critical nursery habitats and food web links for many important commercial and recreational fishery resources including: bonefish, snook, tarpon, permit, pink shrimp, spotted seatrout, oysters, clams, blue crabs and stone crabs, baitfishes; and, numerous coral reef fishes that include snappers, groupers, grunts, barracuda, spadefish, spiny lobster, parrotfish, surgeonfish and triggerfish. The production dynamics of these valuable natural resources are inextricably linked not only to fishing and rates of exploitation but also to the spatial distribution and quality of bay waters and habitats, themselves greatly affected by growing human uses and management practices. Since BNP’s natural resources are intimately related to the broader regional ecosystem through water movements and animal migrations, any Park degradation will have consequences well beyond its boundaries. Fishery management strategies now being proposed for BNP require precise spatial data and estimates of resource distribution and status prior to implementation of any spatial management policy. These data will facilitate concise and unambiguous baseline estimation of the Park resource status, provide critical inputs for models used to forecast potential impacts of policy changes, and enable design of an efficient sampling program to monitor future performance of a given management policy. In a proactive movement towards development of strategic planning, this report takes the first steps in establishing the quantitative characterization and assessment of fisheries resources and habitats in BNP. The site characterization was based on an extensive overview and analysis of pertinent scientific and technical literature and biological, fishery, and physical databases relevant to the status and dynamics of fishery resources in Biscayne National Park, Florida. The estimation and simulation modeling “process” involved database assimilation, visualization and mapping of fish-habitat linkages, and multispecies assessments. In the process, we developed a new approach to stock assessment of multispecies coral reef fisheries that compare status of stocks relative to Federal fishery management guidelines. Our assessment research focused on 3 data sets containing more than 25 years of fishery-dependent (1976-1999 via BNP recreational creel survey) and fishery-independent (1979-2000 via SCUBA diver visual census and rollerframe trawls) survey sampling in BNP. Digital maps were created for a variety of spatial “habitats” including bathymetry, benthic substrates, salinity and other water quality parameters that relate to fishery resource distributions and abundances. Biological data were separated into 4 life-stage phases in terms of length for analysis: juveniles; pre-exploited; mature; and, exploited. Habitat data were co-plotted with species life-stage abundance and community diversity distributions to assess the spatial distribution and dynamics of fisheries and their dependence on habitats found in BNP. We noted: C Biscayne Bay plays an important role as primary nursery area for many coastal bay and coral reef fishes and macroinvertebrates (i.e., gray, mutton, lane, schoolmaster and yellowtail snappers; bonefish, tarpon, permit, sharks, molluscs, sponges, snook, seatrout, and pink shrimp, blue crabs, and spiny lobsters). Therefore, we conducted our analyses with respect to the relevant life stages of each species partitioned into four phases: iii juvenile (from length of recruitment to size of sexual maturity); pre-exploited (recruitment length to minimum legal harvest size); mature (length of sexual maturity to maximum size); and, exploited (minimum legal to maximum size). We found that thirty- five (35) species of fish (about 11% of total BNP fishes) were present in all three survey types (TRAWL, CREEL, RVC), suggesting that there is use of habitats amongst lifestage phases. Fish diversity was lowest on the western fringe of Biscayne Bay (particularly at areas proximal to SFWMD canal outfalls and attendant freshwater influxes), increased moving seaward, and was highest in eastern BNP (areas on the barrier coral reef system open towards the Straits of Florida). The diverse spatial patterning of many species distributions reflects specialized ontogenetic use of certain habitats across the seascape. This suggests that a critical mosaic of interconnected habitats may be essential for sustaining fishery resources and ecosystem productivity. We used a systems science approach to conduct a new multispecies assessment on exploited fishery resources found in BNP. The analyses used both fishery-independent and fishery- dependent data sources. We also acquired extensive biological and fishery information on population dynamics including age-growth, age (size) class distribution, and natural mortality rates. We estimated new fishery indicator variables developed from fishery-independent diver visual census data and fishery-dependent creel survey for 91 exploited species to assess the current status of the stocks. However, the reliability of population dynamic parameter datasets for a number of these species were suspect, or unavailable. As a result, this study focused on 35 important reef fish species that reflected the predominance of species and reliable population dynamics data. Commercial fisheries data were also acquired, but were deemed generally unreliable. Combining population-dynamic parameters and estimates of fisheries indices with the LBAR and REEFS assessment models facilitated evaluation of a series of fishery management benchmarks and estimated exploitation levels. We compared these estimates of current stock biomass and fishing mortality levels to the Federal standards. The following points summarize our findings: C For all of the harvested species analyzed, the average sized fish within the exploited phase of these populations for the last 25 years has remained relatively constant and is very close to minimum harvest sizes, not natural historical unfished population size. Many species with extremely low average length in the past have had very little change in average length even though new minimum size limits were imposed. The average size of black grouper is now 40% of what it was in 1940 and the spawning stock is now less than 5% of its historical unfished maximum. C Overall, 77% of the 35 individual stocks that could be analyzed are overfished.