How To Weigh Your Fish With A Ruler

[Dreamtime]

Fish Biologists have collected vast quantities of length and weight data from a variety of fish species. This has enabled length and weight relationships to be calculated for some fish species which can be used to estimate weight of a fish by measuring its length. Please note that these figures are estimates only and individual fish weight will vary depending on age, sex, season and recent feeding activity.

Measuring length

In some of the conversion tables, fork length measurements have been used while in others, total length has been used. Fork length is measured from the snout to the fork of the tail. Total length is measured from the snout to the tip of the tail.

Remember: Legal lengths (total lengths) are measured from the point of the snout to the tip of the tail.

Yellowfin bream (Acanthopagrus australis)

Please note: The following table has fork length measurements. Legal lengths are total lengths and are measured from the point of the snout to the tip of the tail.

Fork Length (cm) Weight (kg) Fork Length (cm) Weight (kg)

25 0.4 48 2.7

26 0.4 49 2.9

27 0.5 50 3.1

28 0.5 51 3.2

29 0.6 52 3.4

30 0.7 53 3.6

31 0.7 54 3.8

32 0.8 55 4.1

33 0.9 56 4.3

34 1.0 57 4.5

35 1.0 58 4.8

36 1.1 59 5.1

37 1.2 60 5.3

38 1.3 61 5.5

39 1.5 62 5.8

40 1.6 63 6.1

41 1.7 64 6.4

42 1.8 65 6.7

43 1.9 66 7.1

44 2.1 67 7.3

45 2.2 68 7.7

46 2.4 69 8.0

47 2.5 70 8.4

Reference: Steffe, A.S., Murphy, J.J., Chapman, D.J., Tarlinton, B.E. and Grinberg, A. 1996. An assessment of the impact of offshore recreational fishing in NSW waters on the management of commercial fisheries. FRDC Project no. 94/053. Publishers, Fisheries Research Institute, NSW Fisheries. 139pp.

Yellowtail Kingfish (Seriola lalandi)

Please note: The following table has fork length measurements. Legal lengths are total lengths and are measured from the point of the snout to the tip of the tail.

Fork Length (cm) Weight (kg) Fork Length (cm) Weight (kg)

60 2.8 94 10.6

61 2.9 96 11.3

62 3.0 98 12.0

63 3.2 100 12.8

64 3.4 105 14.8

65 3.5 110 17.0

66 3.7 115 19.4

67 3.8 120 22.0

68 4.0 125 24.9

69 4.2 130 28.0

70 4.4 135 31.4

71 4.6 140 35.0

72 4.8 145 38.9

73 5.0 150 43.0

74 5.2 155 47.5

76 5.6 160 52.0

78 6.1 165 57.3

80 6.5 170 62.6

82 7.0 175 68.3

84 7.6 180 74.3

86 8.1 185 80.7

88 8.7 190 87.4

90 9.3 195 94.5

92 9.9 200 101.9

Reference: Stewart, J., D. J. Ferrell, B. van der Walt, D. Johnson,and M. Lowry. 2002. Assessment of length and age composition of commercial kingfish landings. Final report to the Fisheries Research and Development Corporation, Project No. 97/126. NSW Fisheries, Cronulla.

Snapper (Pagrus auratus)

Please note: The following table has fork length measurements. Legal lengths are total lengths and are measured from the point of the snout to the tip of the tail.

Fork Length (cm) Weight (kg) Fork Length (cm) Weight (kg)

30 0.6 62 4.5

31 0.7 64 4.9

32 0.7 66 5.4

33 0.8 68 5.8

34 0.9 70 6.3

35 0.9 72 6.9

36 1.0 74 7.4

37 1.1 76 8.0

38 1.2 78 8.6

39 1.3 80 9.2

40 1.3 82 9.8

42 1.5 84 10.5

44 1.7 86 11.2

46 2.0 88 12.0

48 2.2 90 12.7

50 2.5 92 13.5

52 2.8 94 14.4

54 3.1 96 15.2

56 3.4 98 16.1

58 3.8 100 17.1

60 4.1

Reference: Moran M. J. and C. Burton. 1990. Relationships among partial and whole lengths and weights for Western Australian pink snapper Chrysophys auratus ( Sparidae). Fisheries Department of Western Australia, Fisheries Research Report No. 89.

Mulloway (Argyrosomus japonicus)

Total Length (cm) Weight (kg) Total Length (cm) Weight (kg)

45 1.0 112 14.4

46 1.1 116 16.0

48 1.2 120 17.6

50 1.3 124 19.4

52 1.5 128 21.4

54 1.7 130 22.3

56 1.9 135 24.9

58 2.1 140 27.7

60 2.3 145 30.8

64 2.8 150 34.0

68 3.3 155 37.4

72 3.9 160 41.1

76 4.6 165 45.0

80 5.4 170 49.1

84 6.2 175 53.5

88 7.1 180 58.1

92 8.1 185 63.0

96 9.2 190 68.1

100 10.3 195 73.5

104 11.6 200 79.2

108 12.9

Dusky Flathead (Platycephalus fuscus)

Total Length (cm) Weight (kg) Total Length (cm) Weight (kg)

36 0.3 72 2.7

37 0.3 74 2.9

38 0.3 76 3.2

39 0.4 78 3.5

40 0.4 80 3.8

41 0.4 82 4.1

42 0.5 84 4.4

43 0.5 86 4.8

44 0.6 88 5.1

45 0.6 90 5.5

46 0.6 92 5.9

47 0.7 94 6.4

48 0.7 96 6.8

49 0.8 98 7.3

50 0.8 100 7.8

52 0.9 105 9.1

54 1.1 110 10.6

56 1.2 115 12.2

58 1.3 120 14.0

60 1.5 125 15.9

62 1.7 130 18.1

64 1.8 135 20.4

66 2.0 140 23.0

68 2.2 145 25.7

70 2.5 150 28.7

Reference: Steffe, A.S., Murphy, J.J., Chapman, D.J., Tarlinton, B.E. and Grinberg, A. 1996. An assessment of the impact of offshore recreational fishing in NSW waters on the management of commercial fisheries. FRDC Project no. 94/053. Publishers, Fisheries Research Institute, NSW Fisheries. 139pp.

[slinkymalinky]

Wow... I've been aiming too low! Looking forward to tangling with an 8kg bream and a 28kg Flathead

That's a handy conversion chart Mariner... thanks mate, I'll hang onto this.

Cheers, Slinky

[GregL]

Slink

The only prob is I have weighed in a couple of 44cm fork length bream in comps and they have only ever made 1.6kgs MAX.

I wish they weighed the magic 2kg mark!

If it said fork length it would go pretty close give or take 15%.

G

[Hodgey]

The last two bream that I have caught that measured 45cm in total weighed in at 1.62kg and 1.50 kg, so I think the 15% varaiation mentioned by Greg is pretty much on the money.

These measurements are a great guide for those of us who release a lot of our fish without weighing them. Thanks Carl

Hodgey

[Boog's Boat]

I found this somewhere when and took a photo of it can't remember where, just up for comparison sakes. Hope the picture works

Nathan

Edited August 23, 2008 by Boog's Boat

[Josh88]

Seems pretty accurate and useful. We've had quite a few spot on with those weights-lengths and a few fairly different. Usually just measure and weigh when we're out there-provided we didn't forget either.

Josh

[flatty hunter626]

i personally dont find the bream one very accurate. as i hav caught numerous bream over 40cm and they are all around the 1 to 1.1kg mark.......really where did they get 1.6kg from!........they must have been catching some pretty dam fat fish!.

cheers flatty hunter

[bjneville]

Has anyone ever seen a 70cm Bream?!?