Adverse consequences of stock recovery: European hake, a new “choke” species under a discard ban?

Abstract

Many commercial fish stocks are beginning to recover under more sustainable exploitation regimes. In this study, we document the temporal and spatial changes in one remarkable example of stock recovery: northern European hake (Merluccius merluccius). Analysing data from several scientific surveys, we document a dramatic increase in estimates of biomass between 2004 and 2011 throughout the larger area now occupied by the stock. The largest increase occurred in the North Sea, where hake have been largely absent for over 50 years. Spatio‐temporally resolved commercial landings show that high densities occur in the North Sea only between April and September, suggesting a density‐dependent seasonal habitat expansion to suitable temperature and depth conditions. These changes have implications for the management of the stock which are discussed. Notably, if discards are banned as part of management revisions, the relatively low quota for hake in the North Sea will be a limiting factor (the so‐called ‘choke’ species) which may result in a premature closure of the entire demersal mixed fishery in the North Sea, jeopardizing many commercial fisheries in the region. This example of the unforeseen consequences of improved stewardship highlight the need for a more holistic, regional and responsive approach to managing our marine ecosystems.

Temporal and spatial patterns of reproductive indices of European hake ( Merluccius merluccius ) in the northern North Sea and Norwegian coastal areas

“…All these observations suggest that hake inhabits the deep Norwegian trench during winter and spring and moves to shallower coastal and North Sea waters to spawn in summer and autumn (Hickling, 1927;Thomassen, 1974). Potential migration patterns have been proposed (Schmidt, 1909;Hickling, 1927;Hickling, 1930;Thomassen, 1974;Bergstad, 1991;Baudron and Fernandes, 2014) and fish movement can also be seen in temporal or seasonal changes in the length distributions that we observed. However, it is yet unknown to what extent hake populations in different geographical areas interact with each other.…”

“…European hake has historically received little attention in northern Europe, most likely because landings have been comparably low. That situation is changing, and the increasing biomass and spatial extent of the northern hake population has both ecological and economic consequences for the North Sea (Baudron and Fernandes, 2014;Cormon et al, 2014). From 2006-2015 the Spawning Stock Biomass (SSB) of the northern stock increased from 31,772-249,017 t (ICES, 2015).…”

Socio-economic Impacts—Fisheries

“…To allow fishers to adapt to the change, the landing obligation will be introduced gradually, between 2015 and 2019 for all commercial fisheries (species under TACs, or under minimum sizes), however this new measure necessitates that once the least plentiful quota species in a mixed fishery-the 'choke species'-is exhausted, the whole fishery must cease operation. Baudron and Fernandez (2015) have argued that many commercial fish stocks are beginning to recover under more sustainable exploitation regimes and, in some cases, as a result of favourable climatic conditions. For example, northern European hake Merluccius merluccius a warm-water species, witnessed a dramatic increase in biomass between 2004 and 2011 and has recolonised the northern North Sea where hake had largely been absent for over 50 years.…”

“…These changes have implications for the management of other stocks. Notably, if discards are banned as part of management revisions, the relatively low quota for hake in the North Sea will be a limiting factor (the so-called 'choke' species) which may result in a premature closure of the entire demersal mixed fishery (Baudron and Fernandez 2015).…”

First-generation genetic drift and inbreeding risk in hatchery stocks of the wreckfish Polyprion americanus

“…Swartz et al, 2010). Consequently, fisheries catches are now declining (Fisheries FAO, 2012) and their sustainability is seriously questioned in many fish stocks from European waters (Baudron and Fernandes, 2014). Aquaculture has been politically focused, as a worthy alternate to fisheries for it would come to palliate wild fish scarcity and reallocating fishing jobs from the fishing industry.…”