The physical and intellectual work of biomonitoring is viewed as a tool for educating locally, enhancing local awareness of and involvement in conservation issues, and as a springboard for stream restoration and other hands-on conservation activities. It is also making a significant contribution to scientific knowledge of the aquatic communities of our region. A typical day in the field involves application of 3 indices - one each based on fish, benthic macroinvertebrates and physical habitat. Once results from all three are tabulated, the ANAI team and other participants combine results, using a consensus method to arrive at an overall Bioclass Rating - Excellent, Good, Fair, Poor or Very Poor.
Combining results from these methods enables us to calculate numerical indices of stream health, identify trends and suggest solutions to problems. The emphasis here on technical methodology should not obscure the fact that actual monitoring is merely a tool. The effectiveness of the Stream Biomonitoring Program depends on applying biomonitoring information in diverse, flexible and adaptive efforts best categorized under “outreach”. These methods are neither rigidly defined nor described in this section, but examples of their application are highlighted elsewhere in this web page.
DESCRIPTION OF FIELD METHODOLOGY
At each site we apply one of two fish-based sampling methodologies - IBI (Index of Biotic Integrity), based on capture sampling of fish or IBIVI (Visual Index of Biotic Integrity), based on in-stream surveys with face mask and snorkel.
IBI is a widely used index of ecosystem health in aquatic systems (and occasionally elsewhere), which compares the actual composition of an assemblage of organisms (commonly, fish) against a reference condition, based on the least impacted sites in the ecoregion being studied. First developed in the early 1980's it has been adapted for use in all 50 of the United States, Canada, Japan and many European countries. The only tropical country which makes extensive use of IBI is Mexico.
Our program is the first to consistently apply IBI methodology over a period of years in a humid tropical environment. In the early years of the program this necessitated carrying out multiple samples at a great variety of sites in order to derive reference values and formulate an index suitable for our area. Our current indices, adapted to various sizes and gradients of streams, rate stream conditions based on 8 to 11 "metrics" (measurable aspects of a representative sample of fish), then sum the metric scores to arrive at an index value on a scale from 12 (drastically impacted) to 60 (unimpacted natural condition) and assign the corresponding bioclass.
Samples are taken using electrofishers (which stun fish, permitting capture, without causing mortality) and a variety of nets. Provisional results are calculated and interpreted in the field as an educational experience for local volunteer participants.
Our IBIVI is, so far as we know, the first non-capture based method for evaluating the health of fish assemblages in fresh water (although similar methods have been developed for coral reef fish assemblages). It was initially developed to provide an alternative for bioeducators in remote communities who lack access to costly gear and would in any event be unlikely to be able to acquire permits for its use. We subsequently determined that at some sites, particularly larger and deeper clear water streams, it gives better results than capture-based methods. IBIVI was initially developed based on approximations of visually observable aspects of the fish assemblage as compared with counts made using electrofishing gear.
“Benthic macroinvertebrates” comprise all those animals large enough to see with the naked eye which inhabit the bottom of water bodies, comprising insects, crustaceans, worms, mollusks, etc. We sample them with simple nets, applying standard methods used throughout the world in flowing streams, then calculating the BMWP-CR index officially recognized by the government of Costa Rica. One disadvantage of macroinvertebrate work is that it requires preservation of specimens for later identification using microscopes. We are able, however, to arrive at an approximation in the field based on observations made while sampling. This step is extremely important to us since we prioritize sharing results in the field with all participants. Approximation in the field usually errs on the low side, due to non-detection of rare forms.
Some participants are surprised when at times the BMWP and IBI indices give widely varying results. This is not unexpected and reflects the fact that benthic macroinvertebrates are more sensitive to water quality impacts than to all but the most severe alterations of physical habitat. Fish, on the other hand, tend to be more sensitive to habitat disturbances. So the combination of methods helps us paint a more complete picture.
Assessment of physical habitat involves an adaptation of the Stream Visual Assessment Protocol (SVAP) initially developed by the U.S. Department of Agriculture, then adapted for use in Belize by Peter Esselman, and subsequently for the La Amistad Caribe area by ANAI. It is based on observations which can be made during the course of fish and macroinvertebrate sampling, combined with local knowledge provided by participants or streamside residents. In practice the process involves responding to 15 questions about the habitat, followed by discussion among team members.
Use of results:
Typically we are able to carry out one complete biomonitoring site per day. With a full professional crew, we could do up to 3 sites in a day. However, part and parcel of our methodology is the involvement of local people and students not only in the physical work of sampling, but in learning about different species and discussing index results.
Biomonitoring results and index values become increasingly valuable over time, as multi-year data sets permit the identification of trends, and aid in defining problems and problem sources. Results can then be applied in ways which are preventive (e.g. strengthening arguments against dam construction), conservative (creating protections for existing good conditions), corrective (identifying and controlling environmental impacts such as pollution sources) or restorative (reforesting stream banks). Future biomonitoring results can then be used to evaluate the effectiveness of conservation measures. But the most important application of biomonitoring results is undoubtedly in educating and increasing awareness of aquatic biodiversity.
From time to time we incorporate other methods and approaches. One example is our ongoing effort to more fully incorporate the omnipresent freshwater shrimp in our biomonitoring efforts. Shrimp, which physically and behaviorally fall somewhere between fish and benthic macroinvertebrates turn up in most of our samples, and are counted as macroinvertebrates. We are convinced that they represent important information which is not being interpreted, but our efforts to incorporate them are handicapped by lack of knowledge about many aspects of their biology and by the extreme difficulty of differentiating between species in any but the most advanced life stages. For now, shrimp are a matter of internal concern to the Program.
If we are able to obtain necessary permits, in 2018 we hope to initiate collection of American eel tissue samples (fin clips, taken without endangering the life of the animal) to be exported for DNA analysis aimed at improving conservation strategies for this Endangered species. This will involve developing and sharing a variety of new techniques.
If ANAI were an agency concerned only with getting technical results, discussion of “methodology” could end there. However, we view data collection and analysis as only one step in a participatory conservation process which also involves multiple outreach activities. Whereas in the actual work of biomonitoring, as described above, we follow strict methodological protocols, in our non-technical work we strive to be adaptive and at times improvisatory. Here we could offer a multi-page description of methodology used in the non-technical parts of our work. We think it will be more edifying to exemplify those methodologies in other sections of this web page.
Biological Species Guides
Samples of illustrative materials distributed to participants.