How are they doing this?
First of all, juvenile lemon sharks will be tagged, measured and sampled for DNA analysis to add to the collection of nearly 2000 lemon sharks already tagged and sampled from the three sites. The additional samples collected over the next three years will provide long-term data regarding the reproductive patterns and use of different nurseries by female lemon sharks.

The data will also be used to assess and compare the early life history parameters of juvenile lemon sharks in three quite different nursery habitats. The collections at Bimini will also provide the basis for an independent but complementary study on the trophic-dynamics of shark nurseries.
DNA microsatellite genotypes and mitochondrial DNA control region haplotypes will be used to explore genetic relationships among juvenile lemon sharks at a nursery and to look for maternally and paternally related siblings within and across age cohorts. This will allow characterization of breeding patterns and the mating systems of lemon sharks.

At a larger spatial scale, their preliminary data on population genetic structure and gene flows based on microsatellites indicates that the western Atlantic represents a single lemon shark stock, with relatively high levels of gene flow occurring throughout this portion of the species range. The population level analysis will be extended to include samples from disjunct portions of the lemon shark range, the eastern Pacific (coastal Mexico) and the eastern Atlantic (coastal Africa). Both microsatellites and mtDNA sequences will be used to investigate the species-wide population genetic structure.

Data obtained from both types of genetic markers will also be used to investigate the mutational process and rates and patterns of molecular evolution in sharks, utilizing in particular the transisthmian samples separated for approximately 3 million years. Together, the results of this project will characterize the population of biology of a large coastal shark at several spatial scales with a level of detail unprecedented for sharks and indeed most vertebrate species.

Secondly, very little is known about the role of the nursery in the development of the lemon shark. In the absence of parental care, the nursery must provide several fundamental requirements to enable juvenile sharks to survive long enough and grow to a size at which they can leave the nursery. Jacobsen (1987) completed a preliminary energy-flow model of the North Sound based mostly on values from the literature. She suggested that the nursery could support 191 2 kg lemon sharks. We now know the number averages less than 100 at the height of the season. We intend to construct a similar model of the North Sound ecosytem, based on data collected in the field. By doing so, we will have an accurate estimate of the maximum production it can sustain.

In addition, a mass-balanced Ecopath (from Christensen & Pauly, 1992) model will be constructed to ascertain many whole ecosystem properties. The North Sound is a highly enclosed lagoon, making it particularly suitable for mathematical modeling, due to the restricted rate of emigration and immigration and low energy flux to and from the system. This makes it possible to survey the biota with a high degree of certainty. By assessing the standing stocks and primary production rates of mangroves, seagrasses, algae and phytoplankton, we will have an estimate of the total energy available to the system, and a detailed picture of the relative importance of these components to the total primary production. The flow and loss of energy through the food chain is to be measured by surveying the biomass, diet and conversion efficiency of the major consumer groups. This will yield an estimate of the amount of food available to the sharks and show the base upon which it is sustained. Using known values for lemon shark dietary requirements, foraging and conversion efficiencies an estimate of the total sustainable shark production will be calculated.

For the Ecopath model, growth data on the consumer groups is also to be collected. This will provide a detailed description of the dynamics of the ecosystem itself, and enable us to ascertain how it functions with respect to the individual groups and to the stability and robustness of the system. Here, the most useful aspect of Ecopath is that it will provide us with a multiple histogram, showing the impact each group has on each other group.

It is expected that it will show the mangroves, and seagrasses to a lesser extent, as having a large positive impact on virtually every group, and the sharks having a positive impact on the majority of groups. If this expectation is confirmed, it will provide strong evidence that mangroves are of the utmost importance for the survival of almost all the species in the North Sound, and that sharks are highly beneficial to the functioning of mangrove/seagrass communities, adding weight to the argument that sharks are important as regulators of ecosystems.

Ecopath also provides estimates of the level of recycling of energy (through Finn's cycling index), by quantifying the amount of detritus in the system, and how much is transferred to higher trophic levels. This, coupled with the system overhead, will give a useful measure of the stability of the system, because detritus acts as a store of energy. The ability to rebound from perturbation depends to a large extent on these two parameters,
and if they are found to be low, it will have strong implications for local conservation.

How much does this cost?
Approximately $50k a year

What is the next step?
Raise funds, give lectures, get the word out.

What does this all mean?
It will provide evidence that sharks are highly beneficial to the functioning of mangrove/seagrass communities, adding weight to the argument that sharks are vital as regulators of certain ocean ecosystems.