Saving Seafood

NOAA Shipyard Update: NEFSC Fall Research Cruises Will Continue

September 22, 2017 — The following was released by NOAA Fisheries:

The annual NEFSC Fall Bottom Trawl Survey will be conducted on the NOAA Ship Pisces, which is a fishery survey research vessel similar to the Bigelow. Only Georges Bank and Gulf of Maine will be surveyed. The two most southerly areas, the Mid-Atlantic and Southern New England have been dropped.

If all goes smoothly in preparing the Pisces to support the survey, October 16 is the target start date carrying on through November 20.

Fishing gear will be moved from the Bigelow onto the Pisces, and some devices will be installed for monitoring trawl performance while the gear is fishing. Supplies and equipment needed for the survey are already aboard the Bigelow, and will be transferred to the Pisces. The modifications to Pisces are underway.

In a typical year, the Fall Bottom Trawl Survey occupies an average of 377 stations across the Northeast Continental Shelf from the Cape Hatteras to the northern Gulf of Maine in four segments, or legs. Each leg covers a different area beginning in the south and ending in the north.

The number of stations in the Georges Bank and Gulf of Maine survey areas will be similar to past years. Fewer data will be collected at each station because Pisces has less fish handling capacity than the Bigelow. However, samples critical for stock assessments will be collected, including lengths, weights, and hard parts used for aging fish (usually scales and ear bones). Two other NEFSC research cruises planned for this fall were also delayed by the Bigelow repair, and will be conducted on other ships.

The first leg of the Fall Ecosystem Monitoring cruise has been moved to the NOAA Ship Gordon Gunter, an oceanographic research vessel. This cruise collects oceanographic data and plankton samples and has been conducted from the Gunter in the past. There is no firm plan for Leg 2 of this cruise, but the Bigelow is an option if it is ready as scheduled. A beaked whale sighting survey was moved onto a chartered vessel, the R/V Sharp, operated by the University of Delaware, and has been completed with fewer objectives than originally planned.

Meanwhile, repairs continue on schedule for the NOAA Ship Henry Bigelow. The ship is expected back in service in early November 2017.

Read this update on the Northeast Fisheries Science Center website.

New Study Puts Hard Numbers on Impacts of Bottom Trawling

July 24, 2017 — Roughly a fifth of all fish eaten globally are caught using nets towed along the bottom of the ocean. There’s long been concern that this method – known as trawling – destroys or severely damages the ecosystems where it’s used. Now, a new meta-analysis of the science available on this topic offers some quantification of the impacts of different type of trawls.

Previous studies have found that the mud plumes from some trawls can be seen from space, and that “bottom trawling related to commercial fisheries leaves a greater physical footprint on the seafloor than the combined effects of all other human activities, including scientific research, fossil fuel recovery and waste disposal.”

While it is undeniable that dragging metal gear across the seafloor impacts the ecosystems there, a new analysis of seventy different studies finds that not all trawls are equal, and that some do significantly less damage than others.

In particular, otter trawls – the type most commonly used in New England – have the least impact of the four types compared. Otter trawls scrape, on average, just under an inch off the seafloor and remove about six percent of the animals living there. In contrast, hydraulic dredges squirt water into the sediment to release buried animals, reaching about six inches into the sea floor and removing more than forty percent of animals.

Read the full story at WCAI

University of Washington: Bottom-trawling techniques leave different traces on the seabed

July 18, 2017 — The following is excerpted from an article published yesterday by the University of Washington:

Fishing fleets around the world rely on nets towed along the bottom to capture fish. Roughly one-fifth of the fish eaten globally are caught by this method, known as bottom trawling, which has been criticized for its effects on the marine environment.

An international group has taken a close look at how different types of bottom trawling affect the seabed. It finds that all trawling is not created equal — the most benign type removes 6 percent of the animal and plant life on the seabed each time the net passes, while most other methods remove closer to a third. A University of Washington professor is among the main authors on the study, led by Bangor University in the U.K. and published July 17 in the Proceedings of the National Academy of Sciences.

The meta-analysis looks at 70 previous studies of bottom trawling, most in the Eastern U.S. and Western Europe. It looks across those studies to compare the effects on the seabed of four techniques: otter trawling, a common method that uses two “doors” towed vertically in the water or along the bottom to hold the net open; beam trawls, which hold the net open with a heavy metal beam; towed dredges, which drag a flat or toothed metal bar directly along the seafloor; and hydraulic dredges, which use water to loosen the seabed and collect animals that live in the sediment.

“We found that otter trawls penetrated the seabed 2.4 cm (0.94 inches) on average and caused the least amount of depletion of marine organisms, removing 6 percent of biota per trawl pass on the seabed,” first author Jan Geert Hiddink at Bangor University said in a statement. “In contrast, we found that hydraulic dredges penetrated the seabed 16.1 cm (6.3 inches) on average and caused the greatest depletion, removing 41 percent of the biota per fishing pass.”

Depending on the type of fishing gear, penetration depth and environmental variables such as water depth and sediment composition, it took from 1.9 to 6.4 years for the seabed biota, or marine plants and animals, to recover.

“These findings fill an essential science gap that will inform policy and management strategies for sustainable fishing practices by enabling us to evaluate the trade-off between fish production for food, and the environmental cost of different harvesting techniques,” said Ray Hilborn, a UW fisheries professor and one of four co-authors who designed the study.

“There’s a common perception that you trawl the bottom and the ecosystem is destroyed,” Hilborn said. “This study shows that the most common kind of trawling, otter trawling, does not destroy the marine ecosystem, and places that are trawled once a year really won’t be very different from places that are not trawled at all.”

Read the full report here