Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico
description
Transcript of Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico
![Page 1: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/1.jpg)
Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico
Jeff ResterCapstone Project
Master’s of Geographic Information SystemsPennsylvania State University
September 20, 2011Advisor: Dr. Frank Hardisty
![Page 2: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/2.jpg)
The U.S. shrimp fishery targets shrimp across a large portion of the continental shelf in the northern Gulf of Mexico. The fishery is one of the largest and most valuable in the U.S. with approximately 249 million pounds of shrimp caught in the Gulf of Mexico in 2009 with a dockside value of over $325 million.
![Page 3: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/3.jpg)
Shrimp FisheryShrimp are captured using otter trawls towed on the bottom. These trawls capture other demersal organisms and approximately 4.5 kg of bycatch are caught for every 1 kg of shrimp.
Otter Trawl
![Page 4: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/4.jpg)
BycatchBycatch are the unintended fish, invertebrates, and other organisms that are caught along with the targeted shrimp. Much of the bycatch caught in the shrimp fishery is usually returned to the water dead.
Four fish species compose approximately 75% of the shrimp trawl bycatch.
![Page 5: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/5.jpg)
Groundfish Species
![Page 6: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/6.jpg)
Groundfish Fishery
![Page 7: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/7.jpg)
Bycatch Reduction Devices
![Page 8: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/8.jpg)
19811983
19851987
19891991
19931995
19971999
20012003
20052007
20090
50,000
100,000
150,000
200,000
250,000
300,000 Shrimping Effort 1981-2009
Shrimping Effort
Days
Fis
hed
![Page 9: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/9.jpg)
ObjectivesExamine catch per unit effort (number per hour) data from a fishery independent survey from 1987 to 1998 and 1999 to 2009 to determine if abundance levels have changed since the implementation of bycatch reduction devices.
Examine the spatial variation between the periods to determine if and where changes have occurred.
Use species length data to compare average sizes in various areas between the two periods to see if the fish are larger or smaller.
![Page 10: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/10.jpg)
SEAMAP Station Locations
![Page 11: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/11.jpg)
MethodsStandardized the catch rates (number per hour) at each station to allow comparisons between stations.
Analyzed the data distribution and global trends using the Exploratory Spatial Data Analysis tools within ArcMap.
Log transformed (natural log of the catch rate + 1) the data to approach a more normal distribution. Examined various interpolation methods.
Ordinary kriging with a spherical model provided the most robust interpolation method.
![Page 12: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/12.jpg)
MethodsCompared the highly skewed catch data between the time periods using a Mann Whitney U test.
Compared fish lengths between the time periods using a t-test.
![Page 13: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/13.jpg)
![Page 14: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/14.jpg)
![Page 15: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/15.jpg)
![Page 16: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/16.jpg)
![Page 17: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/17.jpg)
![Page 18: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/18.jpg)
![Page 19: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/19.jpg)
![Page 20: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/20.jpg)
![Page 21: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/21.jpg)
![Page 22: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/22.jpg)
![Page 23: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/23.jpg)
![Page 24: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/24.jpg)
![Page 25: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/25.jpg)
![Page 26: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/26.jpg)
![Page 27: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/27.jpg)
![Page 28: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/28.jpg)
![Page 29: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/29.jpg)
![Page 30: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/30.jpg)
![Page 31: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/31.jpg)
![Page 32: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/32.jpg)
![Page 33: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/33.jpg)
![Page 34: Changes in Abundance of Groundfish Species in the Northern Gulf of Mexico](https://reader030.fdocuments.in/reader030/viewer/2022012908/568163a8550346895dd4b7ce/html5/thumbnails/34.jpg)
Remaining WorkExamine possible reasons why some species seem to be increasing in some areas, but not others.
Investigate density dependence to see how it could affect the size distribution of fish.
Examine the weight per hour of fish caught to determine if biomass has increased or decreased.
Multiple regression analysis.