# Presentation: 591907

## Predicted occurrence of coldwater fish assemblages in New Hampshire wadeable streams

**Predicted occurrence of coldwater fish assemblages in New Hampshire wadeable streams**

- By
- David Neils

*Hellgate, Dead Diamond River*

## Purpose

- DES maintains separate dissolved oxygen criteria for “coldwater” streams from Oct. 1 – May 14 (to June 30 for late spawners)
- Strict coldwater fish assemblages are geographically defined; but doesn’t include all streams where more diverse coldwater fish assemblages occur
- Assists in defining where warmwater communities are expected
- Useful for establishing instream water temperature criteria

## Objectives

- To determine if a model could be built that predicts where cold water fish communities are expected occur
- Decide what variables are important in determining the presence or absence of cold water fish communities
- Assess the practicality of applying the model’s results statewide

**Notes:**
Project Objectives

Can a model be built that accurately predicts where coldwater fish communities should or do occur

What are the important environmental variables that determine the presence or absence of coldwater and non-coldwater fish communities

Is the model practical – can it be applied statewide on a consistent basis and improve upon the current application of the DO criteria specific to this community type

## Dataset

- NH DES biomonitoring fish collections 1997 – 2006
- Limited to 1st – 4th order streams sampled from June – August
- 163 stations included in analysis (eliminated sites known to have significant human disturbance
- Broken in calibration (115 sites) and validation (48 sites) datasets
- Analysis based on presence / absence occurrence
- A minimum of 2 individuals collected at site to be considered “present”

## Approach

_**Basic premise:**_ biological assemblages are, in part, structured by the physical and chemical  environmental conditions in which they live.  If distinct biological assemblages can be identified, then the variables that define them can be determined.

_**Approach**_

_**Identification of assemblage types**_

- Species composition indicated these are coldwater

## Identification of target species

**Requirements for target species: **
- Coldwater “specialists”
-  >30 occurrences
- known to have statewide distribution
- native to NH

## Defining the Variables that Structure Coldwater Fish Assemblages

**Latitude** – dd.dddd
**Longitude** – dd.dddd
**Elevation** – feet
**Watershed Area** – square miles
**Gradient** - % slope
**Major River Basin** – Merrimack, Piscataqua, Saco, Connecticut, Androscoggin
**Ecological Drainage Unit (EDU)** – Androscoggin, Upper CT, Lower CT, Merrimack/Coastal

_**Candidate Variables**_

## Independent Consideration of Variables

**Independent Consideration of Variables**

_**Results**_

| Variable | Significance |
| --- | --- |
| Continuous |  |
| Latitude | <0.001 |
| Longitude | 0.396 |
| Drainage Area | <0.001 |
| Elevation | <0.001 |
| Gradient | <0.001 |
| Categorical |  |
| River Basin | <0.005 |
| EDU | <0.005 |

## Distribution of calibration dataset cold and non-cold water fish 

- More frequent in north
- More frequent in smaller watersheds
- Less frequent in Merrimack and Coastal areas
- More frequent in steeper gradients
- More frequent at higher elevations

**Distribution of calibration dataset cold and non-cold water fish **
**assemblages sampled by NH DES biomonitoring unit 1997 – 2006.**

## Simultaneous Variable Consideration

***We need another analysis tool...***
**Logistic Regression: ****yes, I’ll spare you the details**
**What you need to know:**
**Each variable is examined for its relative importance (similar to step-wise linear regression)**
**Regression equation assigns each site a probability (0 – 1) of being a cold (1) or non-cold (0) water fish community based on important variables**
**Predictive accuracy (i.e. # correct predictions) of model as measure of success**

## Slide 11

## Model Results

| Model # | Variables | Overall Predictive Accuracy |
| --- | --- | --- |
| 1 | Elevation | 75.7% |
| 2 | Elevation, Drainage Area | 82.6% |
| 3 | Elevation, Drainage Area, Latitude | 83.5% |
| 4 | Elevation, Drainage Area, Latitude, Longitude | 84.3% |
| 5 | Latitude1, Drainage Area2, Longitude3 | 89.9% (92% present; 86% absent) |

## Environmental Gradient

**Environmental Gradient**

**Increasing probability of occurrence as move from **
**SE to NW and decreasing drainage area**

- South
- East
- Large

- North
- West
- Small

## Small

- Big

## Exploring Predictive Errors (No Model is Perfect!)

**ERRORS**

- Observed Absent

- P(occur) > 0.50; Predict Present

**Type I –** 	Reject null hypothesis when it is true
**For model** – predicting CW present when observed absent
- (6%-cal; 10%-val)

- Observed Present

- P(occur) < 0.50; Predict Absent

**Type II -** 	Do not reject null hypothesis when false
**For model** – predicting CW absent when observed present (5%-cal;6%-val)

- 50% Prob. Is a balanced approach

## Expected Drainages Supporting Coldwater Fish Species

**Expected Drainages Supporting Coldwater Fish Species**

- Small drainages most dominant
-  Larger drainages in north
-  Warmwater streams in white
- Provides definition of streams where coldwater dissolved oxygen criteria should be applied

## Use in Defining Fish Assemblage Types

- DES has defined 3 fish assemblage types: Strict Coldwater, Coolwater, Warmwater

- Is stream expected to supported coldwater fish species
***Use predictive model***

- Yes (_>_0.50)

- No (<0.50)

- Strict coldwater or Coolwater

_**Warmwater**_

_**Strict coldwater**_
- 1) >43.75o latitude & <15mi2
- 2) Ct river basin & 15mi2
- 3) Rest of state >775’ elevation & 15mi2

- Remaining streams

_**Coolwater**_

## Expected Fish Assemblage Types by Drainage

## Correspondence With Water Temperature

- (Lets not forget what we’re talking about)

_**2006/07 Data**_

- Weekly mean
- Clear separation throughout summer
- Cold and cool below thermal thresholds (BT - 22.3oC, Eaton 1995)
- Coolwater ~1o warmer
- Warmwater ~3o warmer

- BT threshold

## 2007 Field Data Verification

**2007 field data:** 18 sites sampled; 15 sites followed modeled predictions (83%) for
-                             fish community type
**Why not perfection?** Model predictions are based on undisturbed sites (lack of
- 	predicted fish community type may indicate “impact”)

## Summary

- Model provides a-priori “tool” for determining ability to support coldwater fish assemblage (~85% accuracy)
- Latitude, drainage area, and longitude most effective unchanging environmental variables for predicting ability to support coldwater fish assemblages; latitude strongest predictor
- Model establishes southeast to northwest gradient for expected presence; tempered by drainage area
- 50% probability of occurrence minimizes predictive errors; balances Type I and Type II (model is neither too conservative nor liberal)
- Identification of drainages where coldwater DO criteria should be implemented
- Model allows for identification of expected fish assemblage types for development / application of appropriate of biological indices
- Recent water temperature data and fish sampling results provide confirmation of model predictions
- Future work should include continued model verification and determination of the utility of additional predictive variables (i.e. groundwater)

## David Neils

- Biomonitoring Program
- NH Dept. Env. Services
- 29 Hazen Dr.
- Concord, NH
- _[dneils@des.state.nh.us](mailto:dneils@des.state.nh.us)_
- 603.271.8865