Lobster reserves in coastal Skagerrak: a field laboratory for science and management

Transcription

1 Lobster reserves in coastal Skagerrak: a field laboratory for science and management Even Moland Esben M. Olsen, Alf R. Kleiven, Halvor Knutsen, Sigurd H. Espeland, Jan Atle Knutsen Institute of Marine Research (IMR), Flødevigen

2 European lobster (Homarus gammarus) Habitat: prefers rocky habitat, from shallow water to > 5 m Feeding ecology: omnivorous Life cycle: pelagic larvae hatch in spring from eggs carried by females during incubation (9 11 months). Postlarvae settle after a 3 8 week pelagic larval duration Fishery: caught by traps during a two month season (October November) by commercial and recreational fishers Conservation status: (Norway) red listed (NT) in 26 & 2 based on fisheries data indicative of historically low abundance

3 Lobster fisheries data, Norway Catch per unit effort ( traps day- 1 )

4 Atlantic cod (Gadus morhua) Commercial and recreational target species Minimum legal size (MLS) 4 cm Coastal cod in Skagerrak is genetically structured into local populations on a scale of 3 km or less Jorde et al. 27, MEPS 343: Photo by Øystein Paulsen used with permission.

5 IMR Flødevigen beach seine time series: 1919 present 5 Cod per haul Sea temperature Foto: Ø. Paulsen

6 What do we need to quantify effects of protection? 1. Control areas: areas that are not protected, where we conduct the same type of sampling 2. before data : sampling prior to impact to describe the situation before protection was introduced 3. Replication: within and among protected and unprotected sites 4. Time R C Norway R Bolærne 59 on Bolærne Kvernskjær C Kvernskjær R Risør C Flødevigen Skagerrak R Flødevigen o E Risør Four experimental MPAs/ lobster reserves in Skagerrak designated September 26: ban on standing gear (only hook and line gear types allowed).

7 Designation of the lobster reserves sparked several studies in addition to the long term monitoring (recently published) One of the northernmost examples of MPA effects to date Two key species A replicated BACI design is still novel and newsworthy in MPA science

8 How did people feel about the lobster reserves? R C Norway R Bolærne 59 on Bolærne Kvernskjær C Kvernskjær Flødevigen C R Risør Flødevigen Skagerrak Questionaire survey conducted in Arendal (Flødevigen) and Hvaler (Kvernskjær) 27: 83 % expected a positive effect on lobster within the areas 7 % expected a positive effect on lobster beyond the areas 88 % of respondents were positive to the idea of using reserves in management of lobster 98 % reported that they had not been involved in the establishment process, but many voiced a wish to be involved in the event of future processes Pettersen et al. 29, In: Integrated Coastal Zone Management, Wiley Blackwell pp o E R Risør

9 Long term monitoring: experimental fishing Bolærne (b) Kvernskjær (c) Three replicate MPA/ control area pairs BACI design pot hauls in MPAs and control areas spread over four days (25 traps x 4) Flødevigen (a) Mean relative change in CPUE Before MPA established MPAs 245 % control areas 87 % Moland et al. 213, PRSB 28:

10 Long term monitoring: experimental fishing Effect of protection on catch per unit effort (CPUE) of lobster in the three replicate MPA control area pairs. Flødevigen Bolærne Kvernskjær Lobsters per trap a Before MPA establ b Before MPA establ c Before MPA establ White bar = control area; grey bar = MPA Moland et al. 213, PRSB 28:

11 Long term monitoring: experimental fishing Effect of protection on mean body size (TL) of lobster in the three replicate MPA control area pairs. Lobster body size, cm a Before MPA est b Before MPA establ c Before MPA establ. MLS Blue symbols = control area; green symbols = MPA Moland et al. 213, PRSB 28:

12 Effect on coastal Atlantic cod (Gadus morhua) white bar = NE control light grey bar = Arendal control green bar = Arendal MPA dark grey bar = SW control Probablity of catch A Arendal MPA( ) Arendal control ( ) Experimental fishing, 2 example: = location of gear (fyke nets) used to sample cod during the 2 field season Mean size, cm B Lillesand SW control % percentile, cm C Risør NE control Moland et al. 213, PRSB 28:

13 3? 1! 4? 2! Build up of higher density (1) and increased mean size (2) has been demonstrated for lobster and cod in experimental MPAs in Skagerrak. It is expected that an increase in density inside MPAs will result in spillover (3), whereas increased density and mean size (1 + 2) will result in increased spawning potential in MPAs relative to adjacent areas, potentially resulting in net export of eggs, larvae and/or juveniles (4) out of MPAs/ marine reserves (recruitment effect).

14 Norway Fl Kv Ri Swe. Kå Skagerrak Den. 23 lobsters tagged in Flødevigen (Fl) and 34 lobsters tagged in Kvernskjær (Kv) lobster reserve in 26. Recovered tags yielded up 1 yr of depth and temperature data. Time of day

15 All data from recaptured tags/ lobsters 2 a S N J M M J S 2 b S N J M M J S Depths inside reserves Depths outside reserves Depth (m) and temperature (C) 2 c e g S N J M M J S S N J M M J S 2 d f h S N J M M J S S N J M M J S S N J M M J S S N J M M J S 2 i j S N J M M J S S N J M M J S Observation period (month) Moland et al MEPS 429:

16 Acoustic tracking: kernel home range (95%UD) for 19 lobsters tracked during in the Flødevigen MPA Lobster home range areas ranged from.6 4 % of total MPA area (1 km 2 ). No significant difference between males, nonovigerous females and ovigerous females for an overlapping observation period of 242 d m Moland et al CJFAS 68:

17 Main conclusions and implications Stakeholder groups with a strong sense of ownership towards a resource can be supportive to protection as a management measure. European lobster populations may recover to natural levels (density/ size and age distribution) in relatively small reserves/ MPAs. Effect of partial protection on density and body size of cod in the Flødevigen MPA (1 km 2 ) indicate that small scale protection may confer benefits to this iconic species. Limited home ranges and high site fidelity are strong indications that coastal reserves of limited size can be designed to afford long term protection to portions of the European lobster population.

18 Funding was provided by the Institute of Marine Research, the Swedish Board of Fisheries, the Research Council of Norway ( Oceans & Coastal Areas programme), and by the EU and Norwegian government through the INTERREG III A programme. even.moland@imr.no Special thanks to Mats Ulmestrand, Hassse Hallbäck, Svein Erik Enersen, Kate Enersen, Hanne Sannæs, Kristian Andvord, Mats Huserbråten, Sebastian Bosgraaf, Pauline Garrigou, Victor Bret and Einar Dahl.