0 10 20 30 40 50 0
1 2 3 4
Calendar week 2010
0 10 20 30 40 50
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18
0.00 0.02 0.04 0.06 0.08 0.10 0.12
cl os e se aso n data are calculated:
1 kg=1 crab
CP U E (N )
9,904 pots
203 lobsters = 286 kg 15,572 pots
29,744 kg = 1,695 crabs missing data are
calculated:
1 lobster=1.5 kg
N and kg per pot lift 2010
CPU E (k g ) CPU E (N a n d k g ) 2006 2007 2008 2009 2010
CP UE
0.00 0.02 0.04 0.06 0.08 0.10 0.12
2006 2007 2008 2009 2010 0
1 2 3 4
0.27t 0.28t 0.45t 0.35t 0.29t 42 t 51 t 42 t 34 t 30 t
Kg per pot lift and day 2006-2010
1960 1970 1980 1990 2000 2010
C a tch (kg )
0 1000 2000 3000 4000 5000 6000
1960 1970 1980 1990 2000 2010 0
10000 20000 30000 40000 50000 Catch (kg) 1960-2010
n. s.
The catchability of the European lobster (Homarus gammarus) and the edible crab (Cancer pagurus) around the island of Helgoland
(North Sea, German Bight)
Isabel Schmalenbach, Michael Janke & Heinz-Dieter Franke
Biologische Anstalt Helgoland, Alfred Wegener Institute for Polar and Marine Research, 27498 Helgoland, Germany
References: (1) Schmalenbach, I., Mehrtens, F., Janke, M., Buchholz, F. (2011). A mark-recapture study of hatchery-reared juvenile European lobsters, Homarus gammarus, released at the rocky island of Helgoland (German Bight, North Sea) from 2000 to 2009.
Fisheries Research 108, 22-30, see doi:10.1594/PANGAEA.727206 for supplementary data. (2) Schmalenbach, I. (2011). Landings of European lobster (Homarus gammarus) and edible crab (Cancer pagurus) in 2010, Helgoland, North Sea. Alfred Wegener Institute for Polar and Marine Research - Biological Institute Helgoland, doi:10.1594/PANGAEA.755534. Pictures: T. Meyer, U. Nettelmann, B. Rauch, I. Schmalenbach, C. Wanke
Acknowledgments: The study was supported by the Ministry of Fisheries and Agriculture of the State of Schleswig-Holstein, Germany. We would like to thank the captain H.-C. Lührs and the crew of the research vessel FK Uthörn for their support in the field.
Helgoland
0 20 40 80
Kilometers 0 1,1002,200 4,400
Meters
Steingrund Sellebrunnknoll
Messstation Elbe
Commercial pot fishery
(1, 2)Monitoring 2010
H. gammarus C. pagurus
At Helgoland waters, the population size of H. gammarus has declined dramatically since the 1960s, and commercial landings of lobsters have been fluctuating over the past decades at a low level of only a few hundred kg per year.
The main competitor of the lobster for food and shelter is the edible crab, C. pagurus.
In 2010, lobsters and crabs were sampled with pots from February to November at three different stations.
The catch per unit effort of lobsters and crabs varied from 0 lobster and 0.04 crabs per pot in winter to 0.08 lobsters and 11 crabs in summer.
Data on catch rates of lobsters and crabs and their seasonal changes around Helgoland may be helpful for fishery and management regulations.
The size of crabs increased while the percentage of females decreased with increasing water temperature. Berried crabs were not captured around Helgoland.
The catchability of lobsters and crabs is related to several environmental variables such as the water temperature and is dependent on their size, sex and specific behavioural patterns.
H. gammarus C. pagurus
H. gammarus C. pagurus
279 pots; 4 lobsters
6 10 15 23 26 28 38 39 47
CPU E
0.0 0.1 0.2 0.3 0.4 0.5
6 10 15 23 26 28 38 39 47 0
5 10 15 20
SST (°C)
0 5 10 15 20
N per pot lift
299 pots; 9 lobsters 323 pots; 8 lobsters
279 pots; 1,062 crabs 299 pots; 1,121 crabs 323 pots; 1,197 crabs
Steingrund Sellebrunnknoll
Sea surface water temperature (SST) Messstation
Temperature (°C)
0 5 10 15 20
CP UE (N lo bster)
0.00 0.02 0.04 0.06 0.08
CP UE (N cr a b )
0 2 4 6 8 10 CPUE vs. temperature
H. gammarus:
y=-0.0013+0.0022x;
r²=0.5160, p<0.05 C. pagurus:
y=-1.7367+0.5192x;
r²=0.8916; p<0.0001
not fished n. f. n. f.
6 10 15 23 26 28 38 39 47
Se x r a ti o (%)
0 25 50 75 100
6 10 15 23 26 28 38 39 47
Si ze (c m )
0 5 10 15
6 10 15 23 26 28 38 39 47 0
5 10 15 20
Carapace length per pot lift Carapace width per pot lift
female: 10.2cm; male: 11.4-13.1cm female: 11.1cm; male: 9.1-15.5cm female: 10.0-10.8cm; male: 11.2-14.0cm
female: 8-18cm; male: 5-21.5cm female: 7-19cm; male: 8-20.5cm female: 7-17cm; male: 6-21.5cm
Sex ratio per pot lift (all stations)
6 10 15 23 26 28 38 39 47 0
25 50 75 100 male
female
Calendar week 2010
n. f.
