In October of 2005, the Division of Marine Fisheries (MarineFisheries ) hosted a workshop on Gulf of Maine Cod. This workshop marked the beginning of a Gulf of Maine cod project in Massachusetts Bay (MassBay) to determine the importance of seasonal abundance in the Commonwealth’s coastal waters. Through the workshop, state, federal, and university-based cod experts from the region were able to share knowledge and advice on the significance of known aggregations and any fisheries prosecuted upon them.

Cod Conservation Zone

The keystone guest was Dr. George Rose, renowned cod expert from Newfoundland who shared his experiences with Canada’s infamous Northern Cod collapse in the early 1990’s and his current research trying to recover that remnant cod population.  Workshop participants viewed extensive data from fishery-dependent and independent sources and concluded that further investigations on the seasonal aggregations would be warranted to improve our understanding and management. MarineFisheries has produced a report of the workshop findings that captures the stock condition, fishery status and suggested areas for further study (see “ MassBay Cod Project: A vital remnant of the Gulf of Maine cod stock?”).

The depleted state of Gulf of Maine (GOM) cod is one of the most pressing challenges facing federal and state fishery managers, at a time that the fishery for cod appears to be growing in state waters. A remnant of the Gulf of Maine stock is found primarily off the Massachusetts coast, as demonstrated by the results of the federally-funded Industry-Based Survey (IBS) for Gulf of Maine Cod . Historic spawning areas along the coast of Maine are no longer producing as they once did (Ames, 2004). Distribution of the Gulf of Maine stock appears to be constricted to the southwestern portion of the GOM, i.e., centered on Stellwagen Bank, MassBay, and Jeffreys Ledge west to the coast off Massachusetts, New Hampshire, and extreme western Maine. 

In September 2005 Gulf of Maine cod management was exacerbated when Groundfish Assessment Review Meeting (GARM) results found fishing mortality rates in excess of the targets and a decline in the spawning stock biomass.  Federal fisheries officials have since called for more controls on fishing including the state waters fishery, not controlled under the Days-At-Sea (DAS) Program. Moreover, there has been an inordinate amount of growth in the state waters fishery by commercial fishermen capitalizing on inshore aggregations and seeking to avoid Amendment 13 related reductions, most notably the multispecies DAS restrictions.

Reacting to the growing problems of the late fall/early winter MassBay cod fishery, the Director with approval of the nine-member Marine Fisheries Advisory Commission closed the most productive grounds in MassBay ( north of latitude 42º 20’and south of 42º 30’ latitude) during December – January 15 (Figure 1). This seasonal closure, which will remain in effect for two years through January 16, 2007, prohibits the harvest of cod by any person. The prohibition applies to recreational and commercial fishermen alike and pertains to all gillnets, otter trawls, mid-water trawls, seines, and all hook-and-line gears including longlines, rod-and-reel, and handlines. Only a few gears: lobster traps and drags for scallops and sea urchins, are to be allowed in the area.

The area also was designated as a Cod Conservation Zone (Figure 1). MarineFisheries took this conservation-based proactive stance on the protection of this vital remnant population.  Effective research and monitoring will allow the agency to be precautionary in its approach to afford sufficient protection while determining future levels of responsible and sustainable levels of harvest from the area.

Industry Based Survey for Gulf of Maine Cod

An IBS vessel
An IBS vessel

The Industry Based Survey (IBS) for Gulf of Maine Cod is a pilot study designed to collect information regarding the distribution of Gulf of Maine (GOM) cod. Funded through the Cooperative Research Partners Program, the IBS is a collaborative effort between the commercial fishing industry, MarineFisheries, Maine Department of Marine Resources, New Hampshire Fish and Game, Rhode Island Department of Environmental Management, and National Marine Fisheries Service, and the Northeast Fisheries Science Center.

As part of its detailed survey of cod populations, to complement existing state and federal surveys, the IBS is in a unique position to provide intensive data within the MassBay Cod Conservation Zone (CCZ).

Now in its third field season, the IBS commenced sampling stations within the CCZ on November 17, 2005 and will continue to sample the area into January of 2006.

Hydroacoustic Survey

Biosonics

In order to examine the spatial extent and the amount of cod associated with the aggregation, an intensive and quantitative sampling effort is required. Relying solely on traditional sampling gear, such as gillnets or trawls, to address this question could have unnecessary detrimental effects on the aggregation itself. An acoustic survey with a scientific echosounder provides a less-invasive method of quantifying the magnitude of the aggregation. However, some gillnetting will still be necessary to groundtruth the targets acquired via the acoustic gear. A pilot study will be applied with acoustic instrumentation and sampling protocols to estimate the biomass of the cod aggregation. Similar work has been accomplished in the Newfoundland fishery by Dr. George Rose. It is also an important goal of this study to determine the optimal time of day based on fish behavior to conduct further acoustic work. This acoustic survey will be a one-time, intensive sampling effort on the cod aggregation, once it has been identified.

This survey will employ a split-beam Biosonics echosounder. Once the cod aggregation has been identified, it will be systematically surveyed using transect lines spaced to cover the entire aggregation. The same area will be surveyed during night hours to record any diel changes in vertical distribution, which could affect detectability with acoustic gear. This survey will be conducted in conjunction with the gillnetting to groundtruth for species composition and size frequency.

Cod Potting

Cod Pots

Long-term sustainable methods of fishing in areas of dense cod aggregations should be explored. The predominant method in the area has been overnight gillnetting, a method that drowns the fish and results in nearly all released fish being killed. Cod pots, recently developed for the Newfoundland cod fishery, are considered a viable alternative gear where discards are a problem. Cod biological sampling with pots may prove quite useful, especially for those studies that rely on the survival of released fish (e.g. tagging and DNA samples). With a presumption of low stress levels in potted fish, pots may also allow blood chemistry comparisons with other gear types. Pol and Walsh (2006, in preparation) began a pilot study of cod pots in MassBay in May and June 2005. A number of questions remained unanswered from previous work: size selectivity of cod pots, whether cod would respond to bait if in spawning or pre-spawning condition, and whether commercial quantities could be caught. The following objectives were identified and accepted:

  1. Conduct a gear experiment using Newfoundland cod pots.
    • Obtain operational information on cod potting, especially economic costs (bait, fuel)
    • Obtain catch information, including:
      • What is the catch rate of the pots?
      • What size cod are caught in the pots?
      • What by-catch species are found in the pots?
    • Obtain biological information and samples as requested. Are cod feeding?
  2. Conduct a gear comparison to cod pots using gillnets.
    • Determine size selectivity of cod pots by comparison to size range caught in multipanel gillnets.
    • Obtain biological information and samples as requested. What are cod eating?

SMAST Tagging

A DST tag
A DST tag

The Cod Tagging Project at SMAST was developed through the Massachusetts Fisheries Recovery Commission (MFRC) and funded through the NOAA Fisheries Northeast Region Cooperative Research Partners Initiative (CRPI). The project was developed to provide a liaison with the fishing fleet and create an industry based program that will provide data on the abundance, distribution, and behavior of commercially fished species and the environment in which they are found. The program utilizes the knowledge and expertise of the local fishing industry to collect and tag cod under normal fishing operations in the Gulf of Maine, Georges Bank, and Nantucket Shoals.

Objectives of the project include:

  • Determine the large-scale seasonal movement patterns of cod throughout the Gulf of Maine and Georges Bank
  • Measure growth rates and recruitment of cod in the wild
  • Evaluate the environmental conditions (temperature, salinity, habitat) in areas where cod are found

Vessels with homeports ranging from Monhegan Island, Maine to Montauk, New York have provided assistance with fish collection and tagging. SMAST personnel also accompany chartered vessels on trips solely dedicated to research activities. As fish are collected and tagged, the location and time of capture are recorded, along with the fish’s length. A small yellow T-bar tag (3” in length) is inserted into the musculature at the base of the fish’s first dorsal fin and the fish are released. The T-Bar tags have a yellow collar on which a unique identification number is printed for fish determination, along with the SMAST name and phone number for reporting recaptured tags. Archival tags are also attached in a similar location on a subset of fish to record environmental parameters such as temperature, depth, and salinity. Each tag contains a unique sequence of numbers that identify the fish and is used to link the tagging data with similar information collected once the fish is recaptured.

SMAST Acoustic-Optical System

An SMAST Acoustic-Optical Frame
An SMAST Acoustic-Optical Frame

An acoustic-optic system (AOS) has been developed to enumerate size and species-specific fish abundance on Stellwagen and Georges Banks. A first-cut array element has been developed and is currently be used for observing cod aggregations in Massachusetts Bay. The acoustic system consists of a 200 kHz electronically steered phased array sonar with a 90 degree by 11 degree coverage area. The optic portion of the system consists of two low-light black and white video cameras that operate together to produce a combined coverage area of 90 degrees by 50 degrees. Six low power laser pointers are incorporated to aid in estimating range and size characteristics of underwater features. Additionally, a steady state light has been incorporated to provide adequate illumination for video sampling during the night hours and at deep depths where there is little to no natural light. The equipment is mounted on a stationary modular frame with an overall height of 5 feet and base dimensions of 6 feet by 6 feet. Sonar data and single frame video images are stored on an on-board hard drive to be downloaded for analysis post-retrieval. Sonar and optic configuration can also be set prior to deployment to optimize resolution and range characteristics unique to the conditions of each deployment environment. The goal of the project is to use the AOS to investigate cod abundance and diel movement as a function of bottom relief.

MIT Passive Acoustics

A deployed AULS
A deployed AULS

MIT has developed innovative, low-cost Autonomous Underwater Listening Stations (AULS). They are built around state-of-the-art digital recording devices know as Nomad Jukeboxes by Creative Laboratories. The normal practice is to leave the AULS deployed for two days, then return to service the unit and redeploy it in the same or a nearby location. The Nomads will capture a maximum of 218 fifteen-minute files, or 54.5 hours of continuous two-channel data when set on its lowest 11,025 Hz., 12-bit sampling rate. The AULS units use HTI (High Tech Industries, Gulfport , MS ) hydrophones which have have built-in preamplifiers that provide sufficient gain to yield –165 dB per volt at 1 mPa. The Nomads have a user-adjustable gain setting from 1 to 15, which we leave on the highest setting. There are much more than fish vocalizations captured by our broadband, omni-directional hydrophone. At times passing vessels or noise from weather-induced sea state dominate the acoustic environment and makes fish sound detection impossible.