Dear all,
One of my projects is to evaluate fish biodiversity in a large catchment. In order to do that, we have collected all previous sampling records (coordinates), and the next step is to identify areas (sub-catchments) that require more sampling sites/efforts for future sampling purposes.
I'd like to know what would be the minimum (or appropriate) number of sampling sites within a sub-catchment (e.g. HydroBasin Lv8 or Lv7) for fish biodiversity sampling purposes. For my previous studies, we usually set at least six sampling sites within a sub-catchment. But I'm not sure if there is a widely used standard when designing fish sampling approaches.
It would be great if anyone is aware of any literature on this topic.
Thank you in advance for your help.
Rui
almost completely depends on what exactly you're trying to find out about the assemblages, the comparisons you're trying to make, and how diverse they truly are. from these papers it sounds like seasonal variability, and maybe reach-scale spatial variability are important to capture in your sample design as well.
Article Estimating local stream fish assemblage attributes: Sampling...
Article Temporal Variability in Stream Fish Assemblage Metrics and I...
It depends on the sanzonality of the capture area and the abundance and variations of the species in the habitat, so you can assume a total of n=20
The answer by "Henry Hershey" is more useful and trustworthy than the other answers, especially the two that rely on Central Limit Theory.
When I was doing my PhD in Fisheries Management and Accounting Systems, the most authoritative book in this area was:
Hilborn, R. and Walters, C.J. 1992. Quantitative Fisheries Stock Assessment:
Choice, Dynamics and Uncertainty. Chapman & Hall of International Thomson Publishing, Toronto, Ontario, Canada.
Right. If you want the statistically most correct sample size then you should keep n=100 but as it can be a bit hectic or against ethics, so n=30 is best and most acceptable. choice of sampling sites will be best on the basis of the variability of the water quality aspects at different locations in your water body.
In order to collect fish sample for fish diversity and the selection of sites the following things should be keep in mind.
Firstly calculate the total length of study area and then divide the study sites on the basis of distance between each site (must be distance of more than 30km). Also know coordinates of the study sites.
Secondly sites can be differentied on the basis of topography of the sites and type of aquatic habitat (pool, riffle and cascade etc)
Thirdly on the basis of human interference, pollution loads, vegetations, and type of surrounding area for the selection of the study sites.
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