Lab

FWCE 110 Introduction to Natural Resources

Laboratory Assignment – Fisheries Ecology

In this lab students will learn how to sample minnow populations using baited minnow traps and how to calculate a Shannon-Wiener Diversity Index to evaluate biological diversity of samples taken in the field. Students will learn the importance of species richness and evenness in contributing to this calculation. Students will also be able to relate the fish population to water quality parameters. The initial data collection will be conducted at Knox Pond. In week two students will receive a second data set from the Mesilla Valley Bosque State Park pond.

Due Date: Individual laboratory report is due in lab on the week of November 11th.

Please refer to handout on writing scientific lab reports when writing your individual report.

Learning Objectives:

When you finish this lab you will:

1. Reinforce use of water quality parameters learned at the beginning of the semester (pH, salinity, water temperature, and water turbidity. Know how these parameters relate to fish populations.

2. Understand what a Shannon-Wiener Diversity Index is and identify factors that contribute to this index, including species richness and species evenness.

3. Understand what a Shannon-Wiener Diversity Index is used for and why it is valuable in ecological studies.

4. Learn to identify some common minnow and fish species.

Equipment

Baited minnow traps set prior to lab to capture minnows.

Data sheets for recording the number of each species caught per trap.

Buckets for holding each sample

Water sampler

Salinity meter

pH meter

Water Temperature meter

Secchi disk

Background Information

Water Quality Parameters

In most ecological studies, it is a common practice to collect data on habitat characteristics where the species occurs. In this case, we will focus on collecting water quality parameters to have an idea of the quality of the water where the fish are living in, and also allows us to provide some descriptions that could later on be used to assess other biological factors.

Water Temperature

Water temperature (°C) has a strong influence on aquatic communities. Temperature influences what organisms can live in our rivers, lakes, and other aquatic environments. Temperature can also have a strong influence on water chemistry, for example, water with higher temperature can dissolve more minerals from rocks. Temperature also influences the amount of dissolved oxygen water is able to hold with less dissolved oxygen at higher temperatures. In deep lakes, there is typically a temperature stratification in the water: The warmer water is on top (epilimnion) and the cold water on the bottom (hypolimnion).

Secchi depth

Secchi depth (m) measures water transparency. Secchi depth is dependent on particles present in the water (e.g., algae), which is also measured by turbidity as well as water color. Brown water (as opposed to clear or blue water) indicates high dissolved organic carbon (DOC) in the water. DOC gets into water bodies when water leaches dead organic material (e.g., leaves and twigs) – it is basically the same mechanism when you brew tea. We will measure water transparency using a Secchi disk. This is a metal disk attached to a metered cord that measures the water depth at which the disk is no longer visible.

pH

pH is the concentration of hydrogen ions in water and is determined by environments surrounding the water body. Changes in pH can be attributed to natural or human-caused phenomena. Changes in pH can disrupt or even kill organisms within the water body. pH measures the acidity or alkalinity of a solution on a logarithmic scale with 7 being neutral, lower values being more acidic and higher values more alkaline.

Salinity

Salinity is the dissolved salt content of a body of water and is measured in Practical Salinity Units (PSU), this measurement is similar to parts per thousand (PPS). Ocean water has around 35 PSU and everything below 3 PSU is considered freshwater. Salts that are dissolved in water include compounds such as sodium chloride, magnesium sulfate, potassium nitrate, and sodium bicarbonate. Salinity has a large influence on organisms that inhabit a particular body of water and the plants that grow in and around that body of water. Plants that are adapted to saline conditions are referred to as halophytes. Salts enter water naturally through dissolution of soil, rock, and organic material. Human activities also influence salinity levels through the application of fertilizers, manure, wastewater treatment facilities, etc. In some cases, freshwater systems have turned brackish through human activities.

Fish Communities

One important way to compare aquatic systems is to measure biological diversity in the different bodies of water by comparing diversity values for different groups of taxa. For example, comparing groups such as diversity of aquatic insects, comparing minnows, comparing predatory fish, etc. In order to do this, you must learn what the valuable components of a diversity index are, including species richness, species evenness and how these two components combine to arrive at an estimate of diversity. Normally you would compare diversity among two or more sites(bodies of water). As a lab, we will be working in Knox Pond so you will compare diversity of minnows caught in traps in three different areas of the pond compared to Mesilla Valley Bosque State Park pond data that has already been collected. We are doing it this way as many of you have not sampled fish before and we have limited time for lab.

Important Definitions related to Fish Communities

Species Richness – the number of individual species that occur in a sample. The more species present the “richer” the sample.

Species Evenness – this is a measure of the relative abundance of each species in a sample. For example, you may have a sample with 3 species present but “Species One” may make up 90% of all species within the sample indicating although 3 species are present, 2 may be relatively rare. Alternatively, your sample could be more robust with each species represented close to equally in each sample.

Shannon-Wiener Diversity Index – this is a measure of species diversity that takes into account both species richness and species evenness. The equation for this index is

s

H = - ∑ (Pi * ln Pi)

i=1

H = the Shannon Wiener Diversity Index

Pi i= the proportion of each species in the sample

S = the number of species

= the sum from species 1 to S

** Shannon-Wiener Diversity Index is calculated on Excel Worksheet – please see Canvas

Higher values of H represent more diverse communities (or samples). A value near 0 would indicate that only one species was present. If species are evenly distributed than the H value would be high as H is indicative of not only the number of species but also how species are distributed in a sample.

Lab Procedures

1. Assessing water quality – Sample three locations – each in the general vicinity of the minnow traps.

a. Secchi Disk – Performed by two individuals so not to disturb the water surface.

i. Lower the Secchi Disk into the water (usually done from a boat) until it disappears, (note the depth on the cord).

ii. Slowly pull disk up until you see it again (note the depth on the cord)

iii. Average the two depths and record on data sheet

b. Water temperature, pH and salinity – Use the respective meters to collect readings for each of these parameters, follow the procedure explained in part a.

2. Assessing fish community

In this lab we will use the Shannon-Wiener Diversity index to compare the contents of three minnow traps set in different areas of Knox Pond and the Mesilla Valley Bosque State Park Pond. This will be done separately for each lab. Since the Knox pond is small you should expect that you will have similar species diversity (due to similar richness and evenness) in the three areas (i.e. three traps) of the pond. However, the Mesilla Valley Bosque State Park, we may have more diversity based on size of the pond and proximity to the Rio Grande and irrigation ditches.

Minnow traps will be baited with dog food the morning prior to the lab. Traps will be set at different areas (simulated habitat types) of the pond. Students will retrieve traps and empty contents into a large bucket. All minnows within each trap will be identified and counted. Data will be recorded on your data sheets. Minnows from that sample will be immediately released and contents of the next sample (trap) will be evaluated.

Week 1

Baited traps set out by TA’s

Water quality measurements taken at all sites before traps collected

Traps collected – one at a time by FWCE 110 students

Contents of trap 1 is emptied into a bucket where minnows are counted, identified, numbers entered on to data sheet and released.

Same procedure is used for traps 2 and 3.

Week 2

Students review Shannon Wiener Diversity index in class and collectively calculate a diversity index for your class.

1. Create a table that illustrates the species caught & amount by class for each pond and the Shannon Wiener Diversity index for each class at each pond. Please also show in your text how you calculated this index.

2. Create a bar graph that shows the number of species caught for each class for each pond.

3. Create two pie charts that show the percentage of each species caught as a portion of the entire sample (i.e. all species caught for all classes) for each pond. These graphs should provide the reader with a summary of all the species caught and their respective proportions in each pond.

4. Create a bar graph presenting the mean water quality parameters for each class in the Knox pond compared to the Mesilla Bosque State Park.

*Note: Some of the information needed to answer these questions is not readily available on the data sheet and will require you to make calculations using data found on several sheets.