Science

What happens when you fish too long and too hard in one spot?

Science clearly supports a need for better ecosystem-based management. Image via NOAA FishWatch.

This week, the New England Fishery Management Council will consider a range of measures to address localized depletion in the Atlantic herring fishery. Atlantic herring (also known as “sea herring”) is a lynchpin species in New England’s ocean. It is a forage fish. That is, Atlantic herring serve as an important food source for larger fishes (including many we like to catch and eat), whales, and seabirds. Because Atlantic herring play such a critical role in the ocean food web, localized depletion of Atlantic herring puts the health of New England’s ocean ecosystems, other fisheries, and even the fishery that specifically targets sea herring at risk. Given Atlantic herring’s importance to the ecosystem, fisheries, and livelihoods, this issue calls for a delicate balancing act to be sure.

Some spokespeople for the Atlantic herring industry claim that there is a lack of science “proving” that Atlantic herring can suffer localized depletion, and cite this as justification for delaying action. In fact, science clearly supports a need for better ecosystem-based management. Localized depletion of forage fishes has real, adverse impacts on the forage species itself, on the rest of the ocean ecosystem, and on coastal communities. The Council should recognize the important ecosystem role of forage species, and adopt management measures that protect forage fish populations from the intensive and concentrated fishing effort they are currently experiencing.

Localized depletion is a scientifically documented phenomenon 

Localized depletion occurs when heavy fishing pressure in a specific area results in a loss of abundance of fish in that area. The depletion is described as “localized” because it may be independent of the overall stock size (Pikitch et al. 2012; McGilliard et al. 2011). Localized depletion can be seen in multiple fish stocks, and its biological and ecological impacts can be major.

Localized depletion negatively impacts Atlantic herring

The biological impacts of localized depletion refer to impacts on the target species itself, which can be amplified in spatially complex populations (Ciannelli et al. 2013). If the management of a species is based on a geographical scale that is larger than the scale of important population dynamics of that species (a common situation), localized depletion can occur (McGilliard et al. 2011; Wilson 2006; Ames 2004). For example, Atlantic herring behave in a somewhat predictable manner. During the summer and fall months, individuals will congregate in large, dynamic and spatially complex spawning aggregations. Concentrated fishing pressure on the spawning fish can alter the age structure of the population by selectively removing the larger, older, reproductively viable individuals from the population (Brander et al. 2010).

Another way that localized depletion can result in a loss of population sub-components is by leaving “holes” in the geographic extent of a larger population, particularly when the sub-populations have low-mixing rates. This is due to the fact that migrants cannot move in fast enough to replace the amount of fish being removed from the population in that area (Barbeaux et al. 2014; Ciannelli et al. 2013). In doing so, the integrity of the larger population structure of a species – this is essential to a species’ resilience – can be lost (Ciannelli et al 2013). For example, managers report that Atlantic menhaden populations are not overfished and overfishing is not occurring; however, the population has yet to be restored to its historic geographic range along the entire Atlantic seaboard. Furthermore, we sometimes set fishery rebuilding targets to embarrassingly low levels as compared to historic abundances. Such diminished populations can be fished sustainably, but they are also especially vulnerable. This is a risky practice for our most important forage fish.

Localized depletion threatens ecosystem health and functioning

The ecological impacts of localized depletion refer to impacts on the broader ecosystem, such as a disruption in predator-prey dynamics. As prey species are removed in a short amount of time from a specific area, the predators who have little ability to find food elsewhere can be negatively affected (Plaganyi and Essington 2014; Plaganyi and Butterworth 2012; Maryland Sea Grant 2009; Hewitt et al. 2004). We can see multiple examples of this in our local waters on the Atlantic coast and beyond.

For instance, there are concerns that intense fishing of Atka mackerel and Atlantic pollock has impacted the recovery potential of sea lion populations in Alaskan waters (Barbeaux et al. 2014; Witherell et al. 2000). Additionally, in the North Sea, localized depletion of sand eel, an important prey species, has been linked to reduced reproduction and population abundance of seabirds (Daunt et al. 2008; Rindorf 2000), and in Antarctica, heavily concentrated trawl fishing for krill in coastal waters has led to localized depletions and potential negative impacts on Southern Ocean food webs (Werner 2015).

In all of these cases above managers have implemented measures to help minimize the effects of localized depletion on the target species and their predators.

In the case of Atlantic herring, a particular concern among fishery managers and stakeholders is localized depletion altering the seasonal availability of herring as a food source. The loss of herring as a food source could have detrimental effects on inshore groundfish populations, survival of Atlantic puffin and tern chicks, and the local abundance of whales, dolphins, and other marine life (Breton & Diamond 2014; U.S. Department of Commerce 2010; Bakun et al. 2009).

Without Council action on localized depletion, the health of our ocean ecosystem is at risk

These ecological and biological impacts of localized depletion are just some of the negative consequences of failing to manage fisheries on an ecosystem-based level. There is also the potential that these effects will translate to negative economic impacts on our fisheries, whale and bird watching industries, recreational fishing, and the certainty of having healthy fisheries in the future.

At its upcoming meeting, the Council would be wise to address localized depletion in the Atlantic herring fishery and give localized depletion the importance it deserves. The health of our ocean ecosystem is at stake.



References

Ames E (2004) Atlantic Cod Stock Structure in the Gulf of Maine. Fisheries Research 29:10-28.

Bakun A, Babcock EA, Santora C (2009) Regulating a complex adaptive system via its wasp- waist: grappling with ecosystem-based management of the New England herring fishery. ICES Journal of Marine Science 66:1768-1775.

Barbeaux SJ, Horne JK, Ianelli JN (2014) A novel approach for estimating location and scale specific fishing exploitation rates of eastern Bering Sea walleye pollock (Theragra chalcogramma). Fisheries Research 153:69-82.

Brander K, Botsford L, Ciannelli L, Fogarty M, Heath M, Planque B, Shannon L, and Wieland K (2010) Human impacts on marine ecosystems. In: Barange M, Field JG, Harris RP, Hofmann EE, Perry IR, Werner F (eds) Marine ecosystems and global change. Oxford University Press, New York, NY, p 41–72.

Breton AR, Diamond AW (2014) Annual survival of adult Atlantic Puffins Fratercula arctica is positively correlated with Herring Clupea harengus availability. Ibis 156:35-47.

Ciannelli L, Fisher JAD, Skern-Mauritzen M, Hunsicker ME, Frank KT, Bailey KM (2013) Theory, consequences and evidence of eroding population spatial structure in harvested marine fishes: a review. Marine Ecology Progress Series 480:227-243.

Daunt F, Wanless S, Greenstreet SPR, Jensen H, Hamer KC, Harris MP (2008) The impact of the sandeel fishery closure on seabird consumption, distribution, and productivity in the northwestern North Sea. Canadian Journal of Fisheries and Aquatic Science 65:362–381.

Hewitt R, Watters G, Trathan PN, Croxall JR, Goebel ME, Ramm D, Reid K, Trivelpiece WZ, Watkins JL (2004) Options for allocating the precautionary catch limit of krill among small-scale management units in the Scotia Sea. CCAMLR Science 11:81–97.

Maryland Sea Grant (2009) Menhaden species team: background and issue briefs. Paper presented at the Ecosystem Based Fisheries Management for Chesapeake Bay. College Park, MD.

McGilliard CR, Hilborn R, MacCall A, Punt AE, Field JC (2011) Can information from marine protected areas be used to inform control-rule-based management of small-scale, data-poor stocks? ICES Journal of Marine Science 68:201–211.

Pikitch E, Boersma PD, Boyd IL, Conover DO, Cury P, Essington TE, Heppell SS, Houde ED, Mangel M, Pauly D, Plagányi ÉE, Sainsbury K, Steneck RS (2012) Little fish, big impact. Managing a crucial link in ocean food webs. Lenfest Ocean Program, Washington, D.C.

Plagányi ÉE, Butterworth DS (2012) The Scotia Sea krill fishery and its possible impacts on dependent predators: modeling localized depletion of prey. Ecological Applications 22:748-761.

Plagányi ÉE, Essington TE (2014) When the SURFs up, forage fish are key. Fisheries Research 159:68-74.

Rindorf A, Wanless S, Harris MP (2000) Effects of changes in sandeel availability on the reproductive output of seabirds. Marine Ecology Progress Series 202:241–252.

U.S. Department of Commerce (2010) Stellwagen Bank National Marine Sanctuary Final Management Plan and Environmental Assessment. National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries, Silver Spring, MD.

Werner R (2015) Penguins and krill: life in a changing ocean. Journal of Antarctic Affairs 1:37-48.

Wilson JA (2006) Matching social and ecological systems in complex ocean fisheries. Ecology and Society 11(1):9.

Witherell D, Pautzke C, Fluharty D (2000) An ecosystem-based approach for Alaska groundfish fisheries. ICES Journal of Marine Science 57:771-777.


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