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The State of the Bay Galveston Bay Area Project

About the Data

Data Source:
The Texas Parks and Wildlife Department (TPWD) Coastal Fisheries Division regularly samples species of finfish, shellfish, and other vertebrates and invertebrates that inhabit the bays and estuaries of the Texas Coast. The resulting coastal fisheries resource database is one of the most extensive along the US Gulf Coast.

The TPWD coastal fisheries resource database is independent of the commercial and recreational fisheries databases maintained by the agency. The coastal fisheries resource database extends from 1976 to the present and is based on a randomized sampling method (sampling locations are not fixed, but are chosen randomly). The database includes information on a host of aquatic plants and animals collected by the agency using a variety of sampling techniques.

The Galveston Bay Status and Trends Project obtains the coastal fisheries resource data from the TPWD on an annual basis to analyze population trends for fish species collected in bag seine, shrimp trawl, gill net, and oyster dredge collections.

Gear Types:
TPWD fisheries data collected with four sampling gear types can be accessed via the Galveston Bay Fisheries Data Portal:


Bag Seine: Bag seines are used to monitor small adult and juvenile species in shallow, shoreline habitats. Bag seines consist of an 18.3 meter long, 1.8 meter deep, net extended between two poles. In the center of the seine is a bag consisting of small mesh (13 mm) where the catch accumulates. The bag is flanked on both sides by wings of a slightly larger mesh net that sweeps or directs the catch into the bag. Each wing of larger mesh net is connected to a pole at either end of the bag seine. The poles are held by two persons who pull the bag seine parallel to the shoreline for a distance of 15.2 meters (50 feet).

Gill Net: Gill nets are used to monitor large adult species of finfish that move along a shoreline. Gill nets are deployed perpendicular to the shore and are typically left overnight for nine hours or more. Gill nets are 182.9 meters long, 1.2 meters deep, and consist of four 45.7 meter panels of varying mesh size (76 cm, 102 cm, 127cm and 152 cm). The end of the gill net with the smallest mesh is set closest to the shoreline. Gill nets are made of clear monofilament line that is difficult to see in the water. A fish is caught when it tries to swim through the gill net and becomes entangled.

Shrimp Trawl: Shrimp trawls are used to monitor species of finfish and invertebrates that inhabit the open bay bottom. Shrimp trawls are towed behind a boat at 3 miles per hour for a ten-minute time period (trawls deployed before 1986 were towed for 15 minutes). The 6.1 meter trawl net has a mesh size of 38 mm. Heavy wooden doors are attached to each end of the shrimp trawl. Panels of netting, or the wings of the trawl, extend from the doors to the center. In the center of the trawl net is the cod-end, or the bag in which the catch accumulates. As the trawl is pulled through the water, the wooden doors spread the trawl net open and drag it along the bay bottom. Finfish and invertebrates such as shrimp and crabs are caught by the trawl’s wings and swept into the cod-end.

Oyster Dredge: Oyster dredges are used to monitor species of shellfish and associated organisms found on oyster reefs. Oyster dredges are made of a 76 mm mesh net basket attached to a toothed metal bar. The oyster dredge is deployed from a boat for a one-minute time period. Oysters and other species living on the oyster reef are scraped into the net as the toothed bar is pulled across the top of the oyster reef.


Sampling Locations

Fisheries data are available for the following Galveston Bay subbays (use the map to select your area of interest): Christmas Bay, West Bay, Upper and Lower Galveston Bay, East Bay, and Trinity Bay. To view information describing specific sampling locations, download the raw data, which include the site’s latitude and longitude.


Catch Per Unit Effort (CPUE)

Rather than analyzing and reporting data as actual number of fish caught, fisheries data are typically reported as Catch Per Unit Effort (CPUE). Because sampling effort may differ from area to area, month to month, or year to year; the number of fish captured must be analyzed in such a way as to standardize the effort that was exerted.

CPUE standardizes catch data based on the amount of the effort (total time or area sampled) exerted.

Bag seine CPUE is reported as number of individuals captured per area sampled (units are in hectares; one hectare is equivalent to 2.47 acres).

Shrimp trawl, gill net, and oyster dredge are reported as number of individuals captured per hour sampled.


How to Cite the Data

All data in the Fisheries Data Portal are publicly available via request from TPWD Coastal Fisheries Division. Graphs and figures generated by this website are available for public use with the following citation:

[HARC] Houston Advanced Research Center. 2010. Galveston Bay Status and Trends Website: Fisheries Data Portal. Funded by the Galveston Bay Estuary Program. Houston, Texas.

Original data source: Texas Parks and Wildlife Department, Coastal Fisheries Division.


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