# Presentation: 491008

## Relationship of Shrimp Trawl Bycatch 

- Derived Red Snapper F-values to
- Effort and Catch, and the
- Number of Samples (trawl tows) Required
- to Estimate Red Snapper Bycatch
- Rick A. Hart and James M. Nance
- NOAA Fisheries Service
- SEFSC
- Galveston Laboratory

## Shrimp trawl bycatch F- values (red snapper) vs. 

**Shrimp trawl bycatch **
**F-value (red snapper)**

- Shrimp trawl bycatch F- values (red snapper) vs.
- offshore effort, 1960 – 2005.

## Shrimp trawl bycatch F- values (red snapper) vs. 

**Shrimp trawl bycatch **
**F-value (red snapper)**

- Shrimp trawl bycatch F- values (red snapper) vs.
- brown shrimp catch, 1960 – 2005.

## Shrimp trawl bycatch F- values (red snapper) vs. 

**Shrimp trawl bycatch **
**F-value (red snapper)**

- Shrimp trawl bycatch F- values (red snapper) vs.
- red snapper bycatch estimates, 1972 – 2003.

## Shrimp trawl bycatch F- values (red snapper) vs. 

**Shrimp trawl bycatch **
**F-value (red snapper)**

- Shrimp trawl bycatch F- values (red snapper) vs.
- total finfish bycatch estimates, 1972 – 2004.

## Shrimp trawl offshore effort vs. year, 1960 – 2005.

**Effort (24 hour days fished)**

## Gulf of Mexico number of observer sampled tows required at the 

**Sample Size (n)**

- Gulf of Mexico number of observer sampled tows required at the
- 0.05 and 0.01 alpha levels with varying precision levels to
- estimate the number of red snappers.

## Eastern Gulf of Mexico number of observer sampled 

**Sample Size (n)**

- Eastern Gulf of Mexico number of observer sampled
- tows required at the 0.05 and 0.01 alpha levels with
- varying precision levels to estimate the number of red snappers.

## Western Gulf of Mexico number of observer sampled 

**Sample Size (n)**

- Western Gulf of Mexico number of observer sampled
- tows required at the 0.05 and 0.01 alpha levels with
- varying precision levels to estimate the number of red snappers.

## Gulf of Mexico number of observer sampled 

**Sample Size (n)**

- Gulf of Mexico number of observer sampled
- tows required at the 0.05 and 0.01 alpha levels with
- varying precision levels to estimate the weight of red snappers.

## Eastern Gulf of Mexico number of observer sampled 

**Sample Size (n)**

- Eastern Gulf of Mexico number of observer sampled
- tows required at the 0.05 and 0.01 alpha levels with
- varying precision levels to estimate the weight of red snappers.

## Western Gulf of Mexico number of observer sampled 

**Sample Size (n)**

- Western Gulf of Mexico number of observer sampled
- tows required at the 0.05 and 0.01 alpha levels with
- varying precision levels to estimate the weight of red snappers.

## Estimation of Sample Sizes (trawl tows) under Varying Levels of Precision Based on the Mean Number of Red Snappers

| Sample Size (n) 99% Confidence Level
 | Sample Size (n) 95% Confidence Level | Within plus or minus the X |
| --- | --- | --- |
| 23,345 | 14,349 | 5% |
| 5,836 | 3,587 | 10% |
| 1,459 | 897 | 20% |
| 365 | 224 | 40% |
| 162 | 100 | 60% |

## Eastern Gulf of Mexico Estimation of Sample Sizes (trawl tows) under Varying Levels of Precision Based on the Mean Number of Red Snappers

| Sample Size (n) 99% Confidence Level
 | Sample Size (n) 95% Confidence Level | Within plus or minus the X |
| --- | --- | --- |
| 29,011 | 17,832 | 5% |
| 7,253 | 4,458 | 10% |
| 1,813 | 1,114 | 20% |
| 453 | 279 | 40% |
| 201 | 124 | 60% |

## Western Gulf of Mexico Estimation of Sample Sizes (trawl tows) under Varying Levels of Precision Based on the Mean Number of Red Snappers

| Sample Size (n) 99% Confidence Level
 | Sample Size (n) 95% Confidence Level | Within plus or minus the X |
| --- | --- | --- |
| 18,442 | 11,336 | 5% |
| 4,611 | 2,833 | 10% |
| 1,153 | 708 | 20% |
| 288 | 177 | 40% |
| 128 | 79 | 60% |