Project contacts: Dr. Gary Nelson, Jennifer Stritzel Thomson, Paul Caruso, John Boardman

Massachusetts is currently home to the largest recreational striped bass fishery in the country. Our total catch of stripers in 2000 alone approached 7.1 million fish. High population abundance of striped bass, the diversity of the Commonwealth's nearshore habitat and many sources of food for stripers are major factors contributing to the success of this fishery. Without a doubt, striped bass are the backbone of our recreational industry and provide enjoyment to hundreds of thousands of recreational anglers each year. Accordingly, we give this important resource a high level of attention by conducting many special investigations and monitoring programs designed to support the regional planning process.

Temperature Preferences

Proposed sampling of Salem Sound for 2006
Proposed sampling of Salem Sound for 2006

In 2006, we conducted a special study to examine the temperature preferences of striped bass during their summer residence. The thermal preferences of striped bass had been described for landlocked populations, but it was unknown if such preferences exist for striped bass in the continuously changing marine environment.
The questions asked were:

  1. What temperatures are experienced by striped bass?
  2. To what extent does the environment influence the temperatures?
  3. Do striped bass exhibit any temperature preferences or detectable behavioral patterns (e.g., day/night differences)?

To determine if striped bass exhibit a preference, temperature in the environment and temperature experienced by individual striped bass was measured and compared. If striped bass experience similar temperature ranges that are available in the environment, they probably have no preference, but if they experience a smaller range in temperature, it would suggest a preference.

The focus of the study in 2006 was Salem Sound, Massachusetts (Figure 1). Monitoring buoys were placed at 15 sites and temperature was recorded every 2 hours at various depths in the water column.  Striped bass were captured, tagged with a temperature-recording logging tag (Figure 2) and released.  The tag recorded temperature every 2 hours.

A 30" bass with the implanted temperature-recording logger tag and backing tag
A 30" bass with the implanted temperature-recording logger tag and backing tag

In total, 24 of the 151 striped bass tagged in June 2006 were recaptured by recreational and commercial anglers in the intervening year. Release sizes of recaptured fish ranged from 21” to 33” total length and fish were at-large from 1 to 351 days (median = 23 days). Most tagged fish (22) were recaptured during June-August 2006 generally <5 nm from the release location. Results reveal that striped bass experienced a wide range of temperatures while at-large during June-August 2006. The temperatures experienced by striped bass ranged from a low of 7.0 (44° F) to a high of 28.5°C (83°F), but most observations (95%) were between 10°C (50°F) and 25.5°C (78°F). Average temperatures while at-large ranged from 15.0°C (59°F) to 22.2°C (72°F). In comparison, the coldest temperature measured at the twelve stations was 6°C (43°F) at 36.5 meters (120 feet) and the warmest temperature measured was 25°C (77°F) at 0.6 meters (2 feet). No day-night differences in temperature preferences were detected.  Comparisons of water depth-temperatures versus striped bass temperatures showed that most striped bass stay in temperatures above 9-10oC (48-50°F), generally found in depths <10 m (30 feet), even though colder temperatures are available. Since they do not appear to go below ten meters due to cold water, striped bass probably forage on benthic prey only when near-shore. Therefore, any impact on economically-important prey like the American lobster may be concentrated to specific shallow-water areas.

Nelson, G. A., M. P. Armstrong, J. Stritzel-Thomson, and K. D. Friedland. 2010. Thermal habitat of striped bass (Morone saxatilis) in coastal waters of northern Massachusetts, USA, during summer. Fisheries Oceanography 19: 370-381.   [link to abstract - contact Gary Nelson for reprint]

Age and Growth Sampling

Atlantic coast states that harvest striped bass are required, as part of the interstate management process, to characterize their landings. Monitoring of age, size, and sex composition of both commercial and recreational catch and landings of striped bass is indispensable for identifying the need for constructive revisions to management strategies and for confirming estimates of population parameters. In Massachusetts, we conduct annual sampling of the commercial harvest at seafood dealerships. Information collected from more than 9,500 stripers beginning in 1982 include length, weight, sex and scales from each fish examined. We also conduct annual sampling of the recreational harvest at several striped bass tournaments. Since 2001, we solicit volunteer recreational anglers to collect scales from harvested and released fish to boost our sampling coverage. We can observe annual "growth rings" on fish scales and use them to estimate age composition of the catches and rate of growth.

Tagging Studies

Tagging and long-term monitoring of tag recoveries improves understanding of distribution of and movement of Atlantic striped bass stocks and generates vital information about annual survival rates. A state-federal cooperative study, now the largest of its kind, has applied tags to more than 370,000 wild and hatchery striped bass since 1985. Massachusetts DMF began a striped bass tagging study in 1991 as part of this ongoing state-federal cooperative effort and has tagged and released over 5,000 fishes. We employ skilled charterboat captains to guide and collect fish from shoal feedings grounds around Cape Cod. Our study furnishes the largest proportion of legal-size fish to this overall effort. Striped bass tagged in Massachusetts' waters have been recaptured as far north as New Brunswick, Canada and as far south as Georgia, USA.

Striped Bass Diet and Bioenergetics

MarineFisheries conducted a study during 1997-2000 to address the issues of forage needs of the recovered striped bass population and the potential impacts of striped bass consumption on economically important prey species. This DMF research project was designed to provide diet information of striped bass and to build a computer-based bioenergetic model that allows us to estimate consumption rates of striped bass for any particular food item, such as river herring, menhaden, and even the commercially- important lobster. We collected diet information from over 3,000 striped bass collected from the North Shore, Cape Cod Bay, and Nantucket Sound regions of Massachusetts. Some findings of the study are summarized below.

We found that, in general, striped bass consumed mostly fish (menhaden, herring, silversides, and sand lance) and invertebrates (crabs, sand shrimp, and sea fleas); however, the amounts eaten varied depending on the month of summer, fish length, and where the striped bass were captured. Large bass (>24 inches) generally ate more invertebrates (mainly lobsters and crabs) than small bass (<24 inches), but small bass ate more fish (mainly menhaden during August-September) than large bass. Striped bass captured from rocky shorelines or offshore waters generally ate more invertebrates than bass captured from estuaries or harbors.

We also found that the striped bass ate different sizes of prey. Fish prey ranged in size from 0.9" to 19" total length, and crab prey ranged in size from 0.1" to 4" carapace width. Individuals of menhaden and sand lance were generally <5" and the three dominant crabs (rock, green, and lady crabs) were generally <3". American lobsters eaten by striped bass were <2" carapace length.

Using the bioenergetic model, we estimated that an "average" striped bass of six years (27 inches in length) must eat about 16 pounds of prey to gain 1 pound in weight during June-September in Massachusetts' waters. Most energy contributing to the growth of this age class comes from different fish prey during June-July, but mainly from menhaden during August-September. These results confirmed the importance of fishes like menhaden to the survival and health of the striped bass population. (see Graph of Consumption below)

Estimated Total Consumption of Prey by Strped Bass