Fish Length at first maturity in Fisheries Conservation. Presentation outline

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1 Fish Length at first maturity in Fisheries Conservation Rodolfo Reyes Jr. Hagnaya Beach Resort, San Remigio, Cebu 24 Feb Presentation outline Importance of knowing the length our fishes mature and are able to lay eggs How fishes grow What is Length at first Maturity? Why allow fishes to grow bigger than Lm? Can we optimize our fishing to get more fish from our fisheries? - Optimal length (Lopt); Optimal length (Lopt); what is Lopt? Philippine fisheries examples Campaigns to catch fishes at > Lm and the desired outcome - Fish Rulers, Maturity Posters Desired impact of these campaigns The fishes in our area Data available and data needed FishBase can help when available data is deficient

2 What we know about your favorite Fishes (from workshop participants favorite fishes lists) Ilak maturity: 25 cm max length: 50 cm Danggit maturity: 14 cm max length: 40 cm Katambak maturity: 24 cm max length: 50 cm Bulis maturity: 24 cm max length: 50 cm Lagaw maturity: 16 cm max length: 22 cm

3 Growth in Fishes Lolong - saltwater crocodile; 6.2 m; 50 years old Bunawan, Agusan del Sur, 2011 Most species, except for birds and mammals, grow throughout their lives!

4 Guiness World Record Largest crocodile ever caught. Unfortunately it died after 2 yrs in captivity in 2013 Bluefin Tuna 580 kg.

5 A giant sea turtle? No, it is just an illusion The Growth of Anduhaw Linf = 33 cm Lm = 19 cm Length Age=10 months 1 year Age 2 years 3 years Anduhaw,, for example, is sexually mature at 19 cm, at the age of 10 months. If you, however, allow it to grow until it dies, it can reach a length of 33 cm.

6 They who grow fast, die young! Different species grow at different rates. Smaller and short-lived species, in general, mature (attain Lm) faster than larger or longer-living living species. Danggit, for example, attain sexual maturity in about 8 months, but they live for while for some Lapu-lapu it can take as long as several years before they reach maturity. They who grow fast, die young! Danggit 14 cm, 8 months 3 years Budboron 18 cm, 1 year 5 years Indangan 20 cm, 1-2 years 5 years Solid 21 cm, 2-3 years 9 years Sambagon 40 cm, 1-2 years 12 years Diwit 40 cm, 2 years 12 years Suno cm, 2-3 years 12 years Maya-maya 30 cm, 3 years 13 years

7 The Growth of Anduhaw Linf = 33 cm Lm = 19 cm Maturity 10 months Age=10 months 1 year Age 2 years 3 years Anduhaw, for example, is sexually mature at 19 cm, at the age of 10 months. If you, however, allow it to grow until it dies, it can reach a length of 33 cm. Determination of Lm - Collect specimens covering the entire range of sizes available. For Timbungan, for example, individuals from 5 cm to 40 cm. - Group the fishes into size 5 cm size classes. - Cut the fishes open and determine the number of mature individuals for each size class. - The size class where half of the individuals examined are mature is the size class containing the Lm.

8 Lm= Juvenile fish Mature fish 100 % 50 % 0 10 cm 20 cm 30 cm 35 cm The Growth of Anduhaw Linf = 33 cm Lm = 19 cm Maturity 10 months Age=10 months 1 year Age 2 years 3 years

9 Geographic variations in Lm and Linf 14 cm 20 cm Bolinao, Pangasinan Puerto Princesa, Palawan What we have discussed so far How fishes grow. - fishes grow throughout their lives until they die. - smaller size fishes grow faster. - fast growing fishes reach maturity quickly. - but they also don t live very long. What Length at first maturity is. - Length at which fishes reach maturity. How Length at first maturity is determined. - Examining the gonads of samples of different sizes.

10 Presentation outline Importance of knowing the length our fishes mature and are able to lay eggs How fishes grow What is Length at first Maturity? Why allow fishes to grow bigger than Lm? Can we optimize our fishing to get more fish from our fisheries? - Optimal length (Lopt); what is Lopt? Philippine fisheries examples Campaigns to catch fishes at > Lm and the desired outcome - Fish Rulers, Maturity Posters Desired impact of these campaigns The fishes in our area Data available and data needed FishBase can help when available data is deficient Definition of Terms Length at first Maturity (Lm) the length at which 50% of individuals in a population are mature. Maximum Length (Lmax) the length of the largest individual caught in a locality. Length infinity (Linf) Length infinity (Linf) the length to which a fish would grow if it were to grow until it dies.

11 Budboron, Camotes Sea, 1988 (BFAR data) - an example of a fishery that could be improved! Budboron, Camotes Sea, 1988 (BFAR data)

12 Bilang ng isda = 2,956 Total weight = 130 kg 16.5 cm Bilang ng isda = 2,956 Total weight = 180 kg We get 38% more fish! Anduhaw, Visayan Sea, 1986 (BFAR data) - optimized harvesting

13 Why allow fish to grow? - We harvest them when they are bigger and we get more fish to eat! - They spawn eggs at least once, and produce the next generation of fishes we can catch. The Fish Ruler and Poster The Fish Rulers and Posters urge fishers to catch, and consumers to buy only fish have reached maturity and have laid eggs to contribute to the next generation of fishes.

14 The Fish Ruler The Fish Ruler shows the Length at maturity of important fish species. It can be customized for a locality (e.g., Tañon Strait) or a fishery (ex., gillnet fisheries). It tells fishers and consumers that fishes smaller than the lengths shown are probably juvenile fish that have not yet to reach maturity and spawned. Maturity Poster The Maturity Poster shows pictures of species in actual size at maturity. The idea is to post these posters in public markets. Consumers can hold up the fish that they are about to buy against the pictures on the poster to know whether the fish has reached maturity.

15 Does FishBase have Lms for my species? Will you find in FishBase Lms for species in your area? Probably yes. FishBase has compiled life history parameters including Lms for most fishes important to fisheries. For species that do not have Lms, FishBase has a modelling tool that provides usable estimates. Check out FishBase and its many Life History Tools for your own work! Tañon Strait Fishes For many Philippine fishes FishBase has compiled Lm estimates from researches, fisheries reports, and student theses. The and Lms management can of be marine accessed key biodiversity by clicking areas on Growth in the More Information Section in the Species Summary in Page. the Philippines, for the present and future generations.

16 FishBase has Lm for many Philippine fishes Summary of discussion How fishes grow What is Length at first Maturity? Why allow fishes to grow bigger than Lm? Can we optimize our fishing to get more fish from our fisheries? - Optimal length (Lopt); what is Lopt? Philippine fisheries examples Campaigns to catch fishes at > Lm and the desired outcome - Fish Rulers, Maturity Posters Desired impact of these campaigns The fishes in our area Data available and data needed for a Fish Ruler and Poster campaign. Where FishBase can help when available data is deficient.

17 End of Presentation Thank you ( ツ )