Delaware Bay NJDEP finfish trawl survey
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http://www.njfishandwildlife.com/artdelstudy09.htm
Another of New Jersey's Priceless Resources - Studying the Delaware Bay
By Jennifer Pyle
Assistant Biologist
July 24, 2009
INTRODUCTION - HISTORY OF FISHERIES SURVEYS
The Delaware Estuary is New Jersey's largest estuary system. The Delaware estuary is a semi-enclosed body of water where freshwater from the Delaware River mixes with salt water from the Delaware Bay. It serves as nursery areas, spawning and feeding grounds, and migratory routes for many recreational and commercial fish.
Bureau of Marine Fisheries biologists within the New Jersey DEP's Division of Fish & Wildlife conduct several surveys each year to study the status of species populations within the estuary. One of these surveys is the Delaware Bay Finfish Trawl Survey.
In 1991, the Division began a Delaware Bay finfish trawl survey of juvenile finfish species to develop indices for comparing the relative annual abundance of selected stocks. The survey was designed to complement a similar effort being conducted on the western side of Delaware Bay by the State of Delaware's Division of Fish and Wildlife and sampling stations were set up within the shallow, near shore waters on the New Jersey side of the bay. Data collected allows biologists to develop relative abundance estimates and length frequencies of estuarine dependent finfish necessary for predicting future fishery trends and harvest potential. (See New Jersey's Priceless Resource - Studying the Delaware River for the report on a related survey.)
Click on the links below for more Delaware Bay Finfish Trawl Survey information:
SURVEY LOCATIONS
EQUIPMENT/METHODOLOGY
CATCH HISTORY
WATER QUALITY
THE FUTURE OF DELAWARE BAY FISHERIES SURVEY LOCATIONS
The number of stations and their locations have varied over the course of the survey. Currently, there are eleven sampling stations located on shoals near the shoreline, extending from Villas in Cape May to the Cohansey River of Cumberland County. These near-shore stations have typically provided greater yields and more species diversity than sampling attempts in deeper waters. Return to top
EQUIPMENT/METHODOLOGY
http://www.njfishandwildlife.com/ima...el09_netsm.jpg
http://www.njfishandwildlife.com/ima...09_trawlsm.jpg
Click images to enlarge Sampling is performed with a 42-foot research vessel, the R/V Zephyrus. As was the case with the number of stations, the months sampled have also varied. During the survey, samples are collected at each location once a month from April to October. Single ten-minute tows are conducted against the tide at each station. All species collected are identified, counted and measured. If counts are high, 50 individual lengths are randomly selected and recorded. For finfish, from 1991 to 1999, total lengths (tip of nose to end of tail) were measured. Since 2000, fork lengths (tip of nose to inside fork of tail) have been recorded for all species with a forked tail. For species with no forked tail, such as Atlantic croaker, a total length is measured.
CATCH HISTORY
The Division has hauled 1,322 tows and caught 349,873 fish for an average of 264 fish per tow since the survey's inception in 1991. A total of 89 different species have been identified with the five most abundant being bay anchovy, Atlantic croaker, weakfish, blue crab and Atlantic herring.
*NOTE: The number of stations, station locations and months sampled from 1991 to 1996 were inconsistent due to personnel constraints and weather conditions. This inconsistency will have an affect on the number of individuals collected and on the annual relative abundance indices for those years, especially for finfish that utilize the Delaware Bay on a seasonal basis.
Summary table of all species caught (pdf, 9kb)
Click on the links below for species related data:
Bay Anchovy (pdf, 40kb)
Atlantic Croaker (pdf, 37b)
Weakfish (pdf, 36kb)
Blue Crab (pdf, 54kb)
Atlantic Menhaden (pdf, 39kb)
Striped Bass (pdf, 35kb)
Unique Species (pdf, 100kb)
For more information about individual species (biology, range, etc), please visit one of the following websites:
www.fishbase.org/
www.asmfc.org/
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THE FUTURE OF DELAWARE BAY FISHERIES
Surveys like this are just the beginning of the stock assessment process for many species. For example, data from this and similar surveys in other states have reflected an increase in the striped bass population along the entire East Coast. They have also shown a decrease within the bay anchovy population.
As with any ecosystem, data collected from the Delaware Estuary surveys show fluctuations among all species. There are constant changes in the size of fish populations due to many environmental factors. While it is not always completely certain why any species population decreases or increases, the Division is planning future research to examine these variations.
Fishery surveys, such as the Delaware Bay Finfish Trawl, are important for ecosystem management. They provide biologists with information relative to the annual abundance and population trends of many species. Without these surveys, biologists would not be aware of the population increases or decreases that predict future fishery management needs. Being conscious of these fluctuations is important when creating recreational and commercial fishing regulations.
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