Management measures are in place to limit impacts on protected species, including Stellar sea lions and some seabirds. These efforts undergo periodic review to ensure they work as intended.
Impacts on Endangered Species Act (ESA) listed Steller sea lions are a concern in both the Gulf of Alaska (GOA) and Bering and Sea Aleutian Islands (BSAI) groundfish fishery management areas. Two distinct population segments (DPS’s), the eastern U.S. and western U.S. segments, are distributed on either side of a boundary extending southeast from Cape Suckling, Alaska (NMFS 2013c). Both populations were listed under the ESA in 1990 (NMFS 2013d); however, the eastern population was delisted in 2013 (NOAA 2013a). The western population retains its listed status.
While the risk of encounters with marine mammals in the GOA and BSAI fisheries is considered remote (NOAA 2011), there is potential for these fisheries to reduce availability of prey items important to Steller sea lion survival (Thompson and Lauth 2012). Studies indicate that Pacific cod in these areas are a key prey species for Steller sea lions, particularly in winter (Calkins 1998; Sinclair and Zeppelin 2002). The fishery operates to a degree in Steller sea lion foraging areas, and overlap in size range of Pacific cod exploited by commercial fisheries and consumed by Steller sea lions has been documented (Livingston 2002; NMFS 2010). As a protective measure, the National Marine Fisheries Service disperses fishing over time and area to avoid impacting key foraging times and locations (haulouts and rookeries) (NMFS 2012); there are similar measures in place for state managed fisheries (NMFS 2010). For federal and parallel state fisheries managed for Total Allowable Catch (TAC), directed fishing on Steller sea lion prey species is prohibited if biomass is projected to decline below B20% (20% of equilibrium spawning biomass) (NPFMC 2013b).
In 2010, NMFS reviewed fishery management actions in the GOA and BSAI to re-assess their impacts on ESA listed species. The result was a draft revised biological opinion concluding that fishing activities operating under the existing fishery management plan were likely to adversely modify the critical habitat of the western DPS of Steller sea lions and jeopardize its existence (NMFS 2010). Based on the analysis, revised protection measures were recommended in three BSAI federal fishing areas selected based on severity of declines in sea lion abundance, importance of habitat and magnitude of fishery impact. No additional protection measures were recommended for the GOA fisheries. Several alternatives to these recommendations, including a preferred alternative with more reduced BSAI fishery closures were outlined in a 2013 draft environmental impact statement (NMFS 2013b). A finalized EIS is expected in 2014.
Seabirds are incidentally impacted by all gear types, and the fishery has the potential to interact with the endangered short-tailed albatross(Phoebastria albatrus) and the threatened Steller’s eider (Polysticta stelleri) (Mohn et al. 2010]. Limits have been determined for the short-tailed albatross: the current ESA Biological Opinion allows for four over a two-year period. Between 2003 and 2012, captures of short-tailed albatross were only recorded in 2010 (2 mortalities) and 2011 (one mortality). No captures of Steller’s eiders were recorded (Zador 2013). Black-footed albatross (Phoebastria nigripes), are captured much more frequently; and while not endangered, they are listed as a Bird of Conservation Concern by the U.S. Fish & Wildlife Service (Zador 2013). This designation implies that this species is likely to become listed under the Endangered Species Act if further protective measures are not implimented. Other PET species potentially caught include Red-legged Kittiwake (Rissa brevirostris), Marbled Murrelet (Brachyramphus marmorata), and Kittlitz’s Murrelet (Brachyramphus brevirostris), although very low numbers or none of these have been reported caught. To mitigate the fishery’s seabird interactions, regulations require longline vessels longer than 60 feet to fly streamer lines of a specific design above their gear, which discourages birds from diving on the baited hooks during setting.
Closed areas are enforced around seabird breeding grounds and longline vessels have introduced devices, especially streamer lines, which have significantly reduced seabird bycatch (Mohn et al., 2010; Zador 2013). These devices are required of longline vessels longer than 60 feet, and serve to discourage birds form diving on the baited hooks during setting. Marine Stewardship Council certification conditions requiring that 1) the interaction of the trawl fishery with seabirds be further explored, 2) that seabird bycatch by the longline sector be determined to the species level, and 3) that impacts of the longline fishery on skate species be determined, were resolved as of the 2012 Gulf of Alaska pacific cod surveillance audit (Rice et al. 2012).
Discards of target and non-target species are monitored by observers and reported publicly. Stock assessment reports tabulate this data (see Tables 2.2 and 2.36 – 2.40 in Thompson and Lauth, 2012, for most recent numbers as of December 2013). Thompson et al. (2009) reports noted that the impact of bycatch of non-target species (or "incidental catch) on the ecosystem is not well understood, but that only eight species or species groups accounted for an average of more than 1,000 t of discards on average between 2005-2009. Ecology of bycaught species, including “estimation of biomass, carrying capacity, and resilience”, has consistently been identified as a data gap in stock assessment reports (Thompson et al. 2009 and 2010; Thompson and Lauth 2011 and 2012; Thompson 2013; Thompson and Palsson 2013).
Bycatch in the longline fishery is dominated by a small number of species. Skates represent the vast bulk of fish bycatch. The estimated take for 2010 in the Alaskan federal groundfish fisheries (Preliminary Seabird bycatch Estimates for Alaskan Groundfish Fisheries, 2007-2010.) was 4,596 total birds. Of these 2,357 or 51% were Northern Fulmars (Fulmarus glacialis), 1,141 or 25% were unidentified gulls, and 647 or 14% were unidentified shearwaters.
Seabird catches have declined recently, with half as many birds caught in 2010 as in 2007, due to the introduction in 2002 of paired bird-scaring streamer lines.
Gears used in this fishery include “bottom contact” types, i.e.: nonpelagic trawl, pot, and hook-and-line gear. Bottom trawls, and to a lesser extent pots and longlines, may disrupt seabed habitat. Managers have responded to this risk and other concerns by closing large areas of the Bering Sea and Aleutian Islands (BSAI) to bottom contact gear (see below under Marine Reserves). Since the early 1990’s an overall decreasing trend has been observed with respect to the amount of potential area disturbed by bottom trawling (Zador 2013). The 2012 ecosystem assessment for the BSAI reported that in 2011, the maximum potential area of seafloor habitat disturbed by bottom trawling decreased dramatically in portions of the Aleutians Islands region (Zador 2012). In the same year, estimates for the Bering Sea region were the largest since 1998; however a slight decrease was estimated for 2012 (Zador 2013).
The productivity of the Bering Sea environment is highly influenced by sea temperature. In 2012, the eastern Bering Sea returned to a more favorable pattern of cooler temperatures similar to those observed between 2007 and 2010 (Zador 2013). Biomass of upper trophic level species in recent years has been increasing and remains above the long-term average. Strong year-classes of Pacific cod as well as pollock since 2006 have contributed to this effect. A peak in zooplankton biomass was indicated in 2009; however overall abundance appears to have been decreasing since that time. Increased abundance of pelagic forage fish and jellyfish may be associated with this trend (Zador 2012 and 2013).
Increasing ocean acidification holds uncertain implications for this fishery, but Arctic and sub-Arctic seas are experiencing rapid change and some may be close to “tipping points” in ocean chemistry. “High latitude seas are a bellwether for prospective impacts of ocean acidification on marine organisms at mid and low latitudes,” write Fabry et al (2009) in an article summarizing recent research on this matter. Rising emissions of carbon dioxide, primarily from smokestacks and tailpipes, are driving this change in ocean chemistry as the gas mixes into seawater.
Fishery effects on the ecosystem are explicitly considered in the stock assessment and management advice. Main concerns identified by assessors during the most recent Marine Stewardship Council (MSC) certification process (Mohn et al. 2010) included the potential for removal of prey needed by other species (e.g. Steller sea lions), gear impacts on habitat, bycatch mortality, and “ghost fishing” by lost gear. However, management action in response to these concerns has been sufficient to the extent that there are no outstanding MSC certification conditions associated with the fishery (Rice et al. 2013).
The Pribilof Islands Habitat Conservation Area and Bristol Bay nearshore waters are closed to all trawling, including pelagic gear. A map of these and other closed areas may be found at the following NOAA website: Bering Sea Habitat Conservation. See figure ES 1.
Major ecological changes are occurring in the Bering Sea, in part due to climate change. The stock assessment takes account of pollock’s temperature-bound habitat preferences.
Last updated on 03 Jan 2014
Many areas in the Bering Sea and Aleutian Islands (BSAI) are closed to bottom trawls as well as other gears as a means of mitigating impacts to habitat, endangered species and unintended bycatch (Zador 2013). Closures intended to protect benthic habitat tend to be year-round, whereas those intended to minimize bycatch or impacts to seabirds and marine mammals are designed to be either year-round, seasonal or dependent on triggers related to catch statistics. New closures have been added over time and as recently as 2011. Some of these, such as those contained within the Arctic Fisheries Management plan and the Northern Bering Sea Research Area guidelines are designed to be in place until sufficient new information exists to allow sustainable fisheries management (NPFMC 2013c).
In sum, there are presently approximately 736,000 nm2 in the BSAI that are potentially subject to bottom trawling closures (Zador 2013). These include 497,000 nm2 that are closed year round either to bottom trawling alone or in combination with additional fishing activities. The remaining roughly 239,000 nm2 are closed either seasonally or as necessary based on triggers. Bottom trawling is also prohibited in most state waters (0-3 mmi from shore).
Early measures to protect Steller seal lions began in 1991 with restrictions on fishing within waters near rookeries and haul outs. More specific closures intended to prevent depletion of prey supplies for Steller sea lions were implemented in 2000, and by 2001 over 90,000 nm2 of the Exclusive Economic Zone (EEZ) were closed to trawling year-round. Additional mitigation for sea lions occurred in 2011, when substantial parts of the Aleutian Islands were closed to trawling for Atka mackerel and Pacific cod (the predominant target species in those areas) as well as longlining for Pacific cod.
The North Pacific Fishery Management Council (NPFMC) established the Aleutian Habitat Conservation Area in 2006, prohibiting bottom trawling fishing methods in an area of 279,114 square miles. This measure was intended to protect vulnerable corals, sponges, and other benthic species (NPFMC 2013c). Smaller additional “habitat areas of particular concern” (HAPCs) were closed to a variety of bottom contact gear in order to protect areas of high density coral aggregations.
In 2008, the NPFMC implemented new measures in the form of year-round closures to bottom trawling in several areas of the Bering Sea. This precautionary freeze on bottom trawling was intended to preserve benthic fish habitat while research plans were developed. At this time, the NPFMC also established the Northern Bering Sea Research Area including the shelf waters to the north of St. Matthew Island (85,000 nm2).
A new fishery management plan for the Arctic implemented in 2009 established additional closures to all commercial fishing in an area totaling nearly 150,000 nm2 (Zador 2013). Some eastern Bering Sea waters are encompassed in the area. This measure is intended to freeze commercial fishing while the effects on commercial fisheries from warming ocean temperatures, migrating fish stocks and shifting sea ice conditions from a changing climate are investigated (NPFMC 2013c).
A synopsis of the above protections and others throughout Alaska can be found at the NPFMC’s “habitat protections” page.
In addition, to the already protected areas in the BSAI, recent concern has been addressed toward canyon habitat along the Bering Sea continental shelf, collectively known as the Bering Sea Canyons (NMFS 2013a). At the NPFMC’s June 2013 meeting, Greenpeace and other environmental groups asked the NPFMC to protect two of these canyons, the Zhemchung and Pribilof canyons (AJC 2013). In response to testimony at this meeting as well as information from a scientific review by National Oceanic and Atmospheric Administration (NOAA) scientists (Sigler et al. 2013, draft ), the council passed a motion to proactively pursue further research on the Bering Sea canyons (NMFS 2013a). The motion contained steps to “identify and validate where necessary areas of coral concentrations for possible management measures for the conservation and management of deep sea corals in Pribilof and Zhemchug canyons”. NOAA’s Alaska Fisheries Science Center has posted an overview of their research plans for the canyons (Rooper et al. 2013), which is available here.