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IOTC-2009-WPEB-06
IOTC Working Party on Ecosystems and Bycatch (WPEB) Mombasa, Kenya
12-14 October, 2009
Size distribution and length-weight relationships for some large pelagic sharks in the Indian Ocean
by
Romanov Evgeny, Romanova Natalya
IRD, UMR 212 EME, Centre de Recherche Halieutique Mediterraneenne et Tropicale Avenue Jean Monnet, BP 171, 34203 Sète Cedex, France * Corresponding author, e-mail: [email protected], Tel : +33 (0)4 99 57 32 05, Fax : +33 (0)4 99 57 32 95
ABSTRACT Size frequencies and L-W relationships for blues shark, oceanic whitetip shark, silky shark and shortfin mako shark caught during Soviet Indian Ocean Tuna Longline Research Programme (SIOTLLRP) in 1961-1989 are presented.
Shark are dominated bycatch species in the Indian Ocean tuna longline (LL) fisheries and important part of non-target catches in purse seine (PS) and gillnet (GILL). However as it was stated by WPEB (IOTC, 2007; 2008) for most of the Indian Ocean shark species basic biological information is not available. This paper represent an attempt to present some basic information such as size composition and length-weight relationships for several abundant shark species recorded in the LL catches during Soviet Indian Ocean tuna longline research programme (SIOTLLRP), which take place between 1961 and 1989 (Romanov et al., 2006). All measurements were taken at sea on fresh individuals. It was inputted into the database, checked for errors and used for develop L-W relationships.
Blue shark Prionace glauca Gear: LL Sample total n=2842 Females n=905 Males n=1922 Sex non recorded n=15
Blue shark, Prionace glaucaboth sexes
50 70 90 110 130 150 170 190 210 230 250 270 290 310 330
FL, cm
0%
5%
10%
15%
Per
cent
of o
bs
N = 2830; Mean = 193.0165; StdDv = 51.333; Max = 311; Min = 57
Figure 1. Size frequency distribution of blue shark individuals caught during SIOTLLRP, (both sexes, individuals with non-recorded sex are discarded).
Blue shark, Prionace glaucaall sexes TW=(0.159e-4)*FL**((2.84554))
40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340
FL, cm
0
50
100
150
200
250
TW, k
g
Figure 2. Length-weight scatterplot and relationship for blue shark (all sexes, n=2842)
Blue shark, Prionace glaucafemales TW=(0.835e-5)*FL**((2.97234))
40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340
FL, cm
0
50
100
150
200
250
TW, k
g
Figure 3. Length-weight scatterplot and relationship for blue shark (females, n=905)
Blue shark, Prionace glaucamales TW=(0.160e-4)*FL**((2.84153))
40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340
FL, cm
0
50
100
150
200
250
TW, k
g
Figure 4. Length-weight scatterplot and relationship for blue shark (males, n=1922)
Oceanic whitetip shark Carcharhinus longimanus Gear: LL, PS Sample size total n=587 (LL: 583/PS: 4) Females n=279 (LL: 278/PS: 1) Males n=305 (LL: 302/PS: 3) Sex non recorded n=3
Oceanic whitetip shark Carcharhinus longimanusboth sexes
50 70 90 110 130 150 170 190 210 230 250
fl
0%
5%
10%
15%
20%
Per
cent
of o
bs
fl: N = 647; Mean = 145.2249; StdDv = 28.6802; Max = 227; Min = 60
Figure 5. Size frequency distribution of oceanic whitetip shark individuals caught during SIOTLLRP, (both sexes, individuals with non-recorded sex are discarded).
Oceanic whitetip shark Carcharhinus longimanusall sexes TW=(.386e-4)*FL**((2.75586))
0 20 40 60 80 100 120 140 160 180 200 220 240
fl
0
20
40
60
80
100
120
140
160
tw
Figure 6. Length-weight scatterplot and relationship for oceanic whitetip shark (all sexes, n=587)
Oceanic whitetip shark Carcharhinus longimanus
females TW=(.508e-4)*FL**((2.70428))
0 20 40 60 80 100 120 140 160 180 200 220 240
fl
0
20
40
60
80
100
120
140
160
tw
Figure 7. Length-weight scatterplot and relationship for oceanic whitetip shark (females, n=905)
Oceanic whitetip shark Carcharhinus longimanusmales TW=(.120e-4)*FL**((2.98524))
0 20 40 60 80 100 120 140 160 180 200 220 240
fl
0
20
40
60
80
100
120
140
160
tw
Figure 8. Length-weight scatterplot and relationship for oceanic whitetip shark (males, n=305)
Silky shark Carcharhinus falciformis Gear: LL Sample size total n=687 Females n=279 Males n=341 Sex non recorded n=3
Silky shark Carcharhinus falciformisboth sexes
50 70 90 110 130 150 170 190 210 230 250 270 290
fl
0%
5%
10%
15%
Per
cent
of o
bs
fl: N = 684; Mean = 159.5782; StdDv = 40.0919; Max = 281; Min = 66
Figure 9. Size frequency distribution of silky shark individuals caught during SIOTLLRP, (both sexes, individuals with non-recorded sex are discarded).
Silky shark Carcharhinus falciformisall sexes TW=(.160e-4)*FL**((2.91497))
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
fl
020406080
100120140160180200220240260
tw
Figure 10. Length-weight scatterplot and relationship for silky shark (all sexes, n=687)
Silky shark Carcharhinus falciformis
females TW=(.118e-4)*FL**((2.97417))
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
fl
020406080
100120140160180200220240260
tw
Figure 11. Length-weight scatterplot and relationship for silky shark (females, n=279)
Silky shark Carcharhinus falciformismales TW=(.282e-4)*FL**((2.8048))
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
fl
020406080
100120140160180200220240260
tw
Figure 12. Length-weight scatterplot and relationship for silky shark (males, n=341)
Shortfin mako shark Isurus oxyrhinchus Gear: LL Sample size total n=906 Females n=375 Males n=503 Sex non recorded n=28
Shortfin mako shark Isurus oxyrhinchusboth sexes
50 80 110 140 170 200 230 260 290 320 350
fl
0%
5%
10%
15%
Per
cent
of o
bs
fl: N = 879; Mean = 186.6286; StdDv = 35.9449; Max = 342; Min = 70
Figure 13. Size frequency distribution of shortfin mako shark individuals caught during SIOTLLRP, (both sexes, individuals with non-recorded sex are discarded).
Shortfin mako shark Isurus oxyrhinchusboth sexes TW=(.349e-4)*FL**((2.76544))
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340
fl
0
50
100
150
200
250
300
350
400
450
500
tw
Figure 14. Length-weight scatterplot and relationship for shortfin mako shark (all sexes, n=906)
Shortfin mako shark Isurus oxyrhinchus
females TW=(.148e-4)*FL**((2.9249))
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340
fl
0
50
100
150
200
250
300
350
400
450
500
tw
Figure 15. Length-weight scatterplot and relationship for shortfin mako shark (females, n=375)
Shortfin mako shark Isurus oxyrhinchusmales TW=(.177e-3)*FL**((2.4601))
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340
fl
0
50
100
150
200
250
300
350
400
450
500
tw
Figure 16. Length-weight scatterplot and relationship for shortfin mako shark (males, n=503)
REFERENCES
IOTC, 2007. IOTC. Report of the Third Session of the IOTC Working Party on Ecosystems and Bycatch (previously the Working Party on Bycatch) Seychelles, 11 - 13 July 2007. 39 p.
IOTC, 2008. IOTC. Report of the Fourth Session of the IOTCWorking Party on Ecosystems and Bycatch Bangkok, Thailand 20 - 22 October 2008. 23 p.
Romanov, E., Sakagawa, G., Marsac, M., Romanova, N., 2006. Historical database on Soviet tuna longline tuna research in the Indian and Atlantic oceans (first results of YugNIRO-NMFS data rescue project). IOTC-2006-WPTT-10 32 p.
