I am intending to study fish species diversity in a Ugandan lake, in order to determine fish species which may be threatened and recommend conservation actions.
A species becomes threatened due to a number of factors including predators, effects to the food chain among others. Therefore it is equally important to advise me about the methods I can use in biodiversity survey and analysis of the whole lake ecosystem.
What methods can be used to study threatened fish species in a lake/species diversity of a lake?
This is a seemingly simple question – until it is unpacked into its components.
1) Threatened Species:
IUCN defines this in various categories, Information below from: IUCN. (2012). IUCN Red List Categories and Criteria: Version 3.1. Second edition. Gland, Switzerland and Cambridge, UK: IUCN. iv + 32pp.
Depending on which of the categories that you think you have, the methods used will differ. A responsible scientist will err on the side of caution and use the least intrusive and the damaging (both to the fish and to the habitat). Your basic premise is that as few as possible, if any fish should be killed in the study with less as you move from VU to EN to CR.
2) What is a lake?
Limnologists in the past have attempted to define this based on thermal stratification as shallow lakes differ in ‘physiology’ from deep lakes. We have shallow water bodies of 2 metres called lakes and we have water bodies of several 100s of hectares called ponds. The areas of the lake, depth of the water, the amount of rooted vegetation in the littoral areas and the circulation pattern of internal currents are some criteria that would determine the type of methods used.
3) The type of fish
If you have some knowledge of the target fish species and you are interested in just that population, you can select a sampling method that would be appropriate to the fish and habitat. For example, if you threatened species is known to be a bottom feeder, then use of near surface gill nets would probably be a waste of time. If you are looking at the entire fish community, you would have to use a suite of methods.
There are several documents which give options and toolkits that are readily available on the internet. I suggest that you visit the following websites:
http://www.michigandnr.com/PUBLICATIONS/PDFS/ifr/Manual/Manual_intra.htm
http://www.env.gov.bc.ca/fish/methods/toolkits/toolkits.html
For a DNA based approach see paper below and their reference list:
Hänfling B1, Lawson Handley L1, Read DS2, Hahn C1, Li J1, Nichols P1, Blackman RC1, Oliver A2, Winfield IJ3
Environmental DNA metabarcoding of lake fish communities reflects long-term data from established survey methods. . Mol Ecol. 2016 Jul;25(13):3101-19. doi: 10.1111/mec.13660. Epub 2016 Jun 1.
1Evolutionary and Environmental Genomics Group (@EvoHull), School of Biological, Biomedical and Environmental Sciences, University of Hull (UoH), Cottingham Road, Hull, HU6 7RX, UK.
2Centre for Ecology & Hydrology (CEH), Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire, OX10 8BB, UK.
3Lake Ecosystems Group, Centre for Ecology & Hydrology (CEH), Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster, LA1 4AP, UK.
4. Species Diversity
Species diversity is usually measured using indices – it is a good idea to go back to basics and consult Whitttaker (1972) to find out which of the many available is best for you.
Whittaker R.H. 1972 Evolution and Measurement of Species Diversity. Taxon
Vol. 21, No. 2/3, pp. 213-251
Published by: International Association for Plant Taxonomy (IAPT) DOI: 10.2307/1218190
Stable URL: http://www.jstor.org/stable/1218190
5) What type of Diversity ? below from https://www.reference.com/
Alpha diversity is the first part of a three-tiered scale for measuring the biodiversity of an area. An area's alpha diversity is a measure of the diversity of species within an ecosystem. Obtaining this measurement usually entails walking the ground and counting or collecting representatives of each species encountered. Alpha diversity is subtly different from the other two measurements, known as beta and gamma. Alpha diversity deals with species in a single area, while beta diversity is a measure of the difference in diversity between ecosystems in a given area. Gamma diversity is an expression of the overall diversity of an area regardless of the ecosystems where the species are found.
Dear Sadat,
Christopher described the complexity of the question very good! Should note only that threatened status means that abundance of species decline day by day. So, do not confuse with rare and sporadic species. So, investigations should be enough permanent. As well, the threatened status can be given for the endemial or relic species. If appear decline of local population of widespread species - hardly ever necessary to give!
Anyway better to protect the area!
Andrey
Thank you so much Christopher Gordon for thoughtfully answering my question, the links you provided are indeed helping me to make my study a reality.
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