Chesfims 2002 July Shoal Survey Summary Report

ChesFIMS 2002 July Shoal Survey Summary Report

Sampling Dates:8 July 2002 – 26 July 2002

Boat Used:20’ Maycraft with a 130 hp engine

MD DNR Co-Principal Investigator:Alexei Sharov

Chief Scientist: Brandon Muffley

Phone Number: (410) 260-8284

E-mail:

Participating Scientists:

1. B. MuffleyMD-DNR8. R. SadzinskiMD-DNR

2. A. SharovMD-DNR9. J. MowrerMD-DNR

3. B. WilliamsMD-DNR10. M. TopolskiMD-DNR

4. K. ThompsonMD-DNR11. A. McCauleyMD-DNR (intern)

5. J. ThompsonMD-DNR12. K. DonaldsonUMD–College Park

6. P. JonesMD-DNR13. J. BallUMD–College Park

7. A. JarzynskiMD-DNR14. J. Zhou MD-DNR

Objectives: Obtain data on relative abundance and biological characteristics of the bentho-pelagic fish community in the extensive shoal habitats (< 5m depth) in the Maryland portion of Chesapeake Bay. Collect and preserve a sub-sample of catch for dietary analysis.

Area of Operation: From the MD line (approximately 37.5ºN) to just south of the Aberdeen Proving Grounds (39.15ºN).

Type of Operations: Conducted 6-minute bottom-water trawls and recorded a number of environmental and water quality variables at 113 stations in 9 different strata in Chesapeake Bay (Table 1, Figure 1).

Data / Specimens Collected: Collected 2,479 fish (over 50 kg) from 28 different

taxonomic categories (Table 1). Preserved (EtOH) samples from approximately 50 stations where targeted species were present in the catch. Environmental and water quality data recorded at each station.

Damage to Gear: On 18 July 2002, one net was torn during a trawl and was unrepairable. We immediately replaced the net with a backup trawl of the same dimensions and mesh size. One a separate occasion (10 July 2002), we replaced a trawl door due to a stretched ring that was causing the one side of the net to twist.

Figure 1. ChesFIMS 2002 July shoal survey station locations.

Cruise Summary:

We started the shoal portion of the survey on Monday, July 8 and finished on Friday, July 26, 2002. This time period included 15 working days, 13 of which were spent sampling. The strata were not sampled in any pre-determined or systematic order but were sampled on particular days based upon weather conditions and crew availability. Once at a particular location, the order in which the stations were sampled was not pre-determined but based upon weather conditions and tide state.

Overall, the July survey was successful and all objectives were met or exceeded. Based upon survey design (random with allocation proportional to strata size), it was determined that 112 stations were required to be sampled and we were able to sample 113 stations (Table 1). We collected fish from 98 of the 113 stations sampled. Accounting for all species and all strata, the overall catch tow-1 was 21.94±27.29 (mean ± SD, range 0 – 183) This was a dramatic decline from July 2001 with an overall catch tow-1 of 81.06 ± 122.52. The Pocomoke Sound and Patapsco strata had the highest catch tow-1 (mean 32.90 ± 41.08 SD, 31.86 ± 18.70, respectively), while the Eastern Bay stratum had the lowest catch tow-1 (mean 5.33 ± 8.15 SD). In total, 2,479 fish were caught from 28 different taxonomic categories with a total catch weight of more than 48 kg. The total number of fish caught in July 2002 was substantially lower than July 2001 (2,473 in 2002 compared to 8,754 in 2001), but the total biomass was higher in 2002 (over 48 kg) compared to 2001 (41 kg). As in May, bay anchovy (Anchoa mitchilli) was the most common fish encountered throughout the bay, followed by the blue crab (Callinectes sapidus). Weakfish (Cynoscion regalis) and spot (Leiostomus xanthurus) were common in Pocomoke and Tangier Sound catches, while white perch (Morone americana) and croaker (Micropogonias undulatus) were common from the Severn/South rivers and north. A summary of the characteristics of all species caught during July is provided in Table 2. We also compared mean catch tow-1 indices for a few common species between May and July 2002 for a monthly comparison (Figure 2), and between July 2001 and 2002 surveys to provide some connection between last years results (Figure 3).

At the end of each trawl, surface and bottom YSI measurements (temp, DO, and salinity) were taken at every station. The meter was not working the day we were sampling off of Calvert Cliffs, 22 July, so we do not have measurements for this area. Salinity ranged from a high of 21.3 in Pocomoke Sound, to a low of 8.0 in the Patapsco stratum. Even though this was our lowest reading for July, salinity in the Patapsco stratum in July was much higher than readings in May when salinity ranged from 0.9 to 4.3. Surface DO readings were variable between strata but within each strata DO was relatively consistent. On average, surface DO ranged from 6.0 – 8.0 mg L-1. Some locations in Tangier sound had reading as high as 10.5 mg L-1, while Eastern Bay and the Severn & South River strata had readings around 5.0 mg L-1. Bottom DO readings rarely fell below 3.5 mg L-1 and were usually greater than 5.0 mg L-1. At a few stations in Eastern Bay bottom DO was below 2.0 mg L-1. Surface temperatures ranged from a high of 28.4°C in Pocomoke Sound on 19 July 2002, to a low of 23.6°C in the Chester River stratum on 12 July 2002.

Table 1. Summary of the July 2002 survey sampling intensity and catch results.

Table 2. Biological characteristics of all species caught during the July 2002 survey.

Figure 2. Monthly catch rate (number/tow) comparisons for a few of the more common species found during the May and July 2002 survey periods.

Figure 3. Yearly comparison of July catch rates (number/tow) for a few of the most common species found during the two survey years. 2001 – 108 trawls in 4 strata; 2002 – 113 trawls in 9 strata.