Delaware Bay NJDEP finfish trawl survey

[ledhead36]

Some of this stuff is pretty informative, some is boring. Anyone who wants can be added to the mailing list by clicking on the links.


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 (http://www.njfishandwildlife.com/marfhome.htm) 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 (http://www.fw.delaware.gov/Pages/FWPortal.aspx) 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 (http://www.njfishandwildlife.com/artdelstudy08.htm) for the report on a related survey.)
Click on the links below for more Delaware Bay Finfish Trawl Survey information:
SURVEY LOCATIONS (http://www.njfishandwildlife.com/artdelstudy09.htm#location)
EQUIPMENT/METHODOLOGY (http://www.njfishandwildlife.com/artdelstudy09.htm#equipment)
CATCH HISTORY (http://www.njfishandwildlife.com/artdelstudy09.htm#catch)
WATER QUALITY (http://www.njfishandwildlife.com/artdelstudy09.htm#quality)
THE FUTURE OF DELAWARE BAY FISHERIES (http://www.njfishandwildlife.com/artdelstudy09.htm#future) 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 (http://www.njfishandwildlife.com/artdelstudy09.htm#top)

http://www.njfishandwildlife.com/images/marine/sample_site_map09sm.jpg (http://www.njfishandwildlife.com/images/marine/sample_site_map09.jpg)
Click to enlarge map (http://www.njfishandwildlife.com/images/marine/sample_site_map09.jpg)
EQUIPMENT/METHODOLOGY
http://www.njfishandwildlife.com/images/marine/artdel09_netsm.jpg (http://www.njfishandwildlife.com/images/marine/artdel09_net.jpg)
http://www.njfishandwildlife.com/images/marine/artdel09_trawlsm.jpg (http://www.njfishandwildlife.com/images/marine/artdel09_trawl.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 (http://www.njfishandwildlife.com/pdf/2009/artdel_species_totals.pdf) (pdf, 9kb)
Click on the links below for species related data:
Bay Anchovy (http://www.njfishandwildlife.com/pdf/2009/artdel_anchovy.pdf) (pdf, 40kb)
Atlantic Croaker (http://www.njfishandwildlife.com/pdf/2009/artdel_croaker.pdf) (pdf, 37b)
Weakfish (http://www.njfishandwildlife.com/pdf/2009/artdel_weakfish.pdf) (pdf, 36kb)
Blue Crab (http://www.njfishandwildlife.com/pdf/2009/artdel_bluecrab.pdf) (pdf, 54kb)
Atlantic Menhaden (http://www.njfishandwildlife.com/pdf/2009/artdel_menhaden.pdf) (pdf, 39kb)
Striped Bass (http://www.njfishandwildlife.com/pdf/2009/artdel_stripedbass.pdf) (pdf, 35kb)
Unique Species (http://www.njfishandwildlife.com/pdf/2009/artdel_uniquesp.pdf) (pdf, 100kb)
For more information about individual species (biology, range, etc), please visit one of the following websites:
www.fishbase.org/ (http://www.fishbase.org/)
www.asmfc.org/ (http://www.asmfc.org/)
Return to top (http://www.njfishandwildlife.com/artdelstudy09.htm#top)

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.
Return to top (http://www.njfishandwildlife.com/artdelstudy09.htm#top)

Information for this article was provided by Principal Biologist Jeffrey Normant, lead investigator of the program. Funding for this survey is supported by the Federal Aid to the Sport Fish Restoration Program (http://wsfrprograms.fws.gov/) administered by the U.S. Fish & Wildlife Service (http://www.fws.gov/).

[skinner]

Some interesting points here---
http://www.njfishandwildlife.com/pdf/2009/artdel_menhaden.pdf
menhaden, in 2009 the average number quadrupled, that is a statistically significant increase. That would lead to the premise that our 2009 menhaden catches or surveys should be high as well. Only time will tell.


http://www.njfishandwildlife.com/pdf/2009/artdel_weakfish.pdf
weakfish, this shows a more credible decline, with a few upward spikes, which could be considered as anomalies. That's why it becomes smart science to look at the data from a few years. I would tend to believe what they are saying here.

[DarkSkies]

Sent in by OGB, thanks:


Striped Bass

Young-of-Year Striped Bass Adult Striped Bass

In the 1980s, there was a moratorium on striped bass fishing. During that time, striped bass numbers increased at arapid rate. Since the 1990s, New Jersey’s striped bass population has seen steady growth.



While striped bass are typically plentiful in the Delaware Bay during the spring, most of the trawl survey takes place between spawning periods. By May, most striped bass have either moved up the Delaware River to spawn, or they have migrated backinto the ocean.

Therefore it is not surprising that the total number caught throughout the entire survey is only 1,279fish. In 2007, the average number per tow reached its peak at 7 fish. Of the total number measured for all years, 91.5%were less than 100 mm (4 inches) in length.

Division of Fish and WildlifeBureau of Marine Fisheries

NJ Department of Environmental Protection
www.NJFishandWildlife.com


http://www.njfishandwildlife.com/pdf/2013/artdel_stripedbass.pdf

[DarkSkies]

This is part of the danger of relying on data where small sample sizes are involved.
Note that according to the folks who wrote this, only 1279 bass have been netted to be part of the stats here....that's 1279 bass....in 21 years.....(the entire survey duration)
http://www.njfishandwildlife.com/pdf/2013/artdel_stripedbass.pdf (http://www.njfishandwildlife.com/pdf/2013/artdel_stripedbass.pdf)
(take a look at the graph in the above example as well)

IMO these figures are useless.
I have already gone into detail, in other threads, why sample size needs to be large enough and from a wide range of collection sources, so that one can have a degree of confidence (statistical term - confidence interval) that the extrapolated data are representative of the actual population you are trying to make assessments about.



**In this case, with striped bass populations numbering in the millions, a sample size of 1279, over a 21 year period, in statistical terms does not produce a high confidence interval....and therefore is not that useful, in determining the health of the biomass.

This is one of the reasons why it is critical for the readers out there to understand data collection methods, and which ones are more effective than others.

Thanks for reading.

[surferman]

The results of the 2014 Delaware Bay Finfish Trawl Survey have been posted on the NJDEP Division of Fish and Wildlife website. The survey allows the division to develop indices for comparing the relative annual abundance of selected stocks. Data is used for predicting future fishery trends and harvest potential which affects seasons and creel limits for commercial and recreational angles.
This is the latest
http://www.njfishandwildlife.com/artdelbaystudy14.htm

[7deadlyplugs]

If you read it they say there are more stripers along the coast. Is that more small stripers being born or more stripers overall. I don't get it?

[lostatsea]

Maybe they are talking about 2011. I read here somewhere that was a strong year for them.

[ledhead36]

If you read it they say there are more stripers along the coast. Is that more small stripers being born or more stripers overall. I don't get it?

I read that and I disagree. Every year there is less and less schoolie stripers in the RB. Last year we didn't start catching bass till almost april. I know it was a cold winter but come on. The schoolies have always been around as long as I have been fishing. Maybe the delaware stock is healthy. you wouldn't say there are more fish if you just fish from the bayshore.

[basshunter]

Maybe they are talking about 2011. I read here somewhere that was a strong year for them.

That has to be the case. They wouldn't have changed the regulations to make the bass limits less if there really were more. Also I believe there is 3 strains of striped bass. The chesapeake the delaware and the hudson. One of them could be in great shape and the others could not. Guess it depends on where you fish.

[jigfreak]

^^^^ Yup and the chesapeake body of fish is definitely in trouble. I believe the delaware is in trouble too cause I have friends who fish there in the spring and the places to catch big bass have dwindled down to maybe 10 in the whole river. that includes the CM rips as well.
Maybe the other tribes are more healthy. When you have at least 1/3 of the fish population out there in trouble it doesn't make sense to say there are more. I'm not really sure. They could be having OK trawl surveys for YOY. compared to bad years maybe it seems like a lot of little stripers are around. I fish ocean and atlantic counties. You can't say that for where I fish thats for sure.

[hookedonbass]

I believe the delaware is in trouble too cause I have friends who fish there in the spring and the places to catch big bass have dwindled down to maybe 10 in the whole river. that includes the CM rips as well.
.

Everyone I know who fishes the db says it has been going downhill. Could be pollution or just less striped bass, not sure which. Definitely something wrong with that population.

[clamchucker]

The latest
http://www.njfishandwildlife.com/artdelstudy15.htm

[seamonkey]

2015 survey seems a little better.
http://www.njfishandwildlife.com/artdelbaystudy15.htm