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Monday, June 28, 2010

Delaware Estuary Striped Bass 2009-2010 population surveys

The Pennsylvania Fish and Boat Commission completed striped bass electrofishing surveys in the Delaware Estuary on May 29, 2009 and May 27, 2010. Striped bass were collected in 2009 from 21 historic striped bass spawning population indexing sites between Rancocas Creek, NJ, across from NE Philadelphia, and the Commodore Barry Bridge, which joins Chester, Pa with Gloucester Co., NJ. In 2010, sampling occurred between Rancocas Creek, NJ and Raccoon Creek, NJ, which is located about a half mile downstream from the Commodore Barry Bridge. The twenty-one index sites have been sampled each May since 1995. In 2009 and 2010 additional electrofishing was completed at Trenton Falls, the upstream limit of the tidal area. Additionally, fish flesh samples were taken for contaminant analyses from two separate groups of striped bass: those between 20-26 inches long and those between 28-37 inches long.

In 2009, thirteen days of electrofishing resulted in a total catch of 259 striped bass between 6 and 49 inches long while in 2010 twelve days of electrofishing resulted in a total catch of 264 striped bass between 5 and 42 inches long. The largest fish captured to date by electrofishing was 49 inches. Pink United States Fish and Wildlife Service tags were inserted into 134 of the striped bass collected in the 2009 survey and 149 in the 2010 survey. See photo 1. Only those fish 16 inches and longer were tagged. The information gathered from anglers, who report catching a tagged striped bass, allows biologists to monitor striped bass movement, determine where Delaware Estuary fish are harvested, estimate their annual fishing mortality, and document angler release rates. The tagging study has also provided evidence that at least some striped bass show fidelity to specific spawning sites.

From 1995-2009 the Pennsylvania Fish and Boat Commission has tagged 3,200 striped bass in the Delaware Estuary and tidal Schuylkill River combined. To date 600 (19%) of the 3,200 tags have been returned. Eleven to thirteen percent of the returns have occurred during the first year that the fish have been tagged. Recreational anglers, including those on charter boats, have accounted for 88% (n=531) of the returned tags, while commercial fishermen have accounted for 8% (n=48). Reporting rates have probably varied among these groups. Four percent (n=21) of the returned tags have been credited to other collections, such as scientific research. Twelve striped bass have been captured twice. Tags have been returned from as far south as North Carolina and as far north as Massachusetts. The greatest percentage of tags by far has been returned from New Jersey (44.5 percent). See Figure 1.

Some striped bass have traveled incredible distances in a short period of time or over a one year period, with some returning to the same site where they had been captured a year or two earlier. Three examples follow.
  • First, a striped bass tagged near the Philadelphia Navy Ship Yard was caught 17 days later by an angler fishing near Cape Cod, Massachusetts.
  • Second, fifteen to twenty striped bass were captured a year or two later by the electrofishing crews from Delaware and Pennsylvania at the same 1000 yd. sampling sites where they had been tagged a year or two earlier.
  • Third, one striped bass tagged near Chester, PA in May, 2009, was caught and released by an angler fishing in Indian River Inlet, DE (near Rehoboth Beach, DE/ Ocean City, MD) in November, 2009, and was then recaptured by an electrofishing crew in May, 2010, at the same site where it was first tagged in 2009.
Analysis of the catch per hour of electrofishing data since 1995 indicated that there has been a downward trend in the total number of striped bass and the number of striped bass between 12 and 27.9 inches electrofished in the Pennsylvania portion of the Delaware Estuary during the spring spawning run. Further analysis revealed, however, that while the trend was downward there was still no statistical difference in the number of fish being captured (the annual abundance indices). Furthermore, the number of large striped bass (28 inches long and longer) has remained relatively stable since monitoring began.

Although an apparent decline in abundance has taken place, the striped bass population is still large and anglers have reported truly excellent catches of striped bass from the Delaware Estuary in recent years. Twenty-five fish days, with fish ranging from 18 to 40 inches or more have been reported by anglers and five to 15 fish angling trips have been commonplace from the end of March through late May. The new (2008) slot limit that pertains only to tidal water in April and May permits the harvest of two fish per day, 20-26 inches long (28 inch minimum size limit, 2 fish per day creel limit the rest of the year), has been well-accepted by anglers. Many anglers continue to catch-and-release fish for sport or do so because of a PCB health advisory in effect. Typical baits are blood worms, cut herring or other fish, live lined fish, and raw clams cut into thirds. Lures may also be productive, although they are not the terminal tackle of choice.

If you plan to fish for striped bass in the Delaware Estuary, it is recommended that you review the Pennsylvania Summary of Fishing Regulations and Laws for the Delaware River and Estuary since striped bass fishing in the Delaware is regulated differently than striped bass fishing in inland Pa. waters and all NJ waters, including the Delaware River and Estuary. The regulations in the Delaware also vary by location (tidal vs. non-tidal) and month. Furthermore, anglers are advised to consult the rear of the Summary Booklet for the health advisory related to these fish.

Figure 1. State-by-state returns of striped bass that were tagged by the PFBC in the Delaware Estuary from 1995-2009. Three thousand two hundred striped bass have been tagged and six hundred tags have been returned.
Figure 1
Note: UN represents tags returned for which no state of capture was identified. 


Striped bass
Area 6 Fisheries Manager Mike Kaufmann with a tagged striped bass. Note the three inch pink spaghetti-like tag near the tip of the pectoral fin on the fish (click here for larger view of tag).


Striped bass
Former Area 6 Fisheries Biologist Bryan Chikotas with a nice female striped bass electrofished from the Delaware Estuary