Replicated marine protected areas (MPAs) support movement of larger, but not more, European lobsters to neighbouring fished areas

Abstract

The European lobster Homarus gammarus is heavily exploited in the Norwegian fishery, and several management actions have been implemented to protect the species. Three marine protected areas (MPAs) excluding all but hook and line type fishing gear were established along the Skagerrak coast in 2006, effectively banning the trap-based fishery for European lobster. Lobster populations within MPAs and adjacent control areas were studied by capture-markrecapture and recovery methods every year from prior to MPA establishment to the present. During 2006−2014, a total of 4682 and 3317 lobsters were captured (including recaptures) in the MPAs and control areas, respectively. In all MPAs, protection led to a shift in demography, with an increase in mean total length of 15% during 2006−2014, thereby opposing the effects of a sizeselective fishery. No difference was found in rates of movement out from MPAs and control areas, but lobsters moving from MPAs and caught in fished areas were significantly larger than lobsters moving out of control areas. In instances where lobsters tagged in a control area moved into an MPA, the immigrating lobsters had a larger body size than the mean in their area of origin. The range of movement undertaken by recovered lobsters extended beyond the home range sizes suggested by previous shorter-term studies, and well beyond the sizes of the small coastal MPAs studied herein. In summary, demographic changes should be accounted for when interpreting the value of spillover from MPAs, and also potential 'spill in' from fished areas to MPAs.

Inter‐ and intra‐specific interactions affecting crustacean trap fisheries—Implications for management

“…This could diminish the ability to detect these population changes altogether. However, while some studies have detected increases in CPUE within MPAs (Nillos Kleiven et al, 2019) and increases in mean size of lobsters within MPAs (Thorbjørnsen et al, 2018), the present study implies that consideration of the increased inhibitory effect of increasing size or density of lobsters should be taken in to account in determining that change.…”

Protected areas buffer against harvest selection and rebuild phenotypic complexity

“…In this sense, harvest of large individuals leaving the MPA and temporary use of the MPA by individuals from control areas (resulting in lower mortality risks) may explain part of the size-dependent survival patterns observed in later years at some MPA-Control area pairs. However, we are cautious with this explanation, as observed movements between MPAs and control areas are sparse (15 and 33 individuals leaving and entering MPAs, respectively; Thorbjørnsen et al 2018), and other still unidentified causes may explain the survival increases seen outside our study MPAs.…”

“…Indeed, high emigration rates have been documented for Atlantic cod in Flødevigen following increases in individual density several years after protection (Fern andez-Chac on et al 2015), and there are indications (i.e., catch per unit effort estimates) that lobster abundance levels have also increased in the studied MPAs (Moland et al 2013). Recently, Thorbjørnsen et al (2018) reported some spillover of large individuals off MPA boundaries in our study system but also some movement from harvested to protected areas (spill-in), especially in the Vestfold sites due to the proximity and existence of habitat corridors between the local MPA and adjacent control area. In this sense, harvest of large individuals leaving the MPA and temporary use of the MPA by individuals from control areas (resulting in lower mortality risks) may explain part of the size-dependent survival patterns observed in later years at some MPA-Control area pairs.…”

“…The species is considered a nocturnal animal, where light hours are generally spent solitary inside shelters on rocky bottoms (Smith et al 1999, Mehrtens et al 2005, Moland et al 2011b). European lobsters rarely move more than a few kilometers for periods up to years (Dannevig 1936, Smith et al 2001, Agnalt et al 2007, Thorbjørnsen et al 2018. Recent shorter-term home-range studies based on acoustic tracking yielded estimates ranging from 0.01 to 0.64 km 2 over periods ranging from several months to nearly 1 yr (Moland et al 2011a, Wiig et al 2014, Skerritt et al 2015.…”

Restoration of Abundance and Dynamics of Coastal Fish and Lobster Within Northern Marine Protected Areas Across Two Decades

“…An increased average body size (13%) of lobster in MPAs relative to controls was evident after 4 years of protection from the annual lobstering season (Moland et al, 2013a), an effect somewhat dampened by introduction of a 25 cm MLS in 2008. Thorbjørnsen et al (2018) presented "before" (2006) and "after" (2014) data on the demography of lobster in the three original MPAs, demonstrating a substantial widening of the size structure in the protected populations compared to the harvested beforestate. By 2014, the average size increase in MPAs was 15% compared to 1% in control areas.…”