respon larva ikan terhadap intesitas cahaya



Cahaya merupakan faktor eksternal dan ekologi yang penting, termasuk spektrum warna, intensitas dan fotoperiodik. Karakteristik cahaya sangat spesifik dalam lingkungan perairan dan sangat bervariasi di alam. Ambang intensitas cahaya minimal yang dibutuhkan untuk perkembangan dan pertumbuhan larva ikan.
Pada kondisi pencahayaan gelap, larva cenderung bergerak menyebar dalam mencari mangsa. Sehingga membutuhkan energi yang lebih tinggi. Aktivitas metabolisme yang tinggi memerlukan energi yang besar sehingga laju penyerapan kuning telurnya menjadi lebih cepat. Larva ikan pada hari pertama setelah menetas tidak ditemukan adanya pigmen pencahayaan pada matanya dan sedikit sekali diferensiasi penglihatan. Pada hari ketiga pigmen dengan retina yang bertingkat dan sel penglihatan telah berkembang. Selanjutnya pada hari kelima saraf optik dan cone (sel berbentuk kerucut pada retina) telah berkembang.
Intensitas dapat bervariasi, sebagai contoh antara 50 dan 150 lux untuk ikan Sparus auratus. Namun, beberapa spesies dapat tumbuh dan berkembang pada intensitas cahaya yang sangat rendah adalah seperti pada beberapa spesies larva ikan pelagis, sementara ikan kakap (Morone saxatilis). Pada saat larva umumnya hidup di daerah estuaria dengan air yang keruh. Juvenil ikan herring Clupea harengus, berenang cepat dan bertahan hidup ketika berpindah ke perairan yang gelap.
Ketika larva berubah menjadi juvenil maka rods (sel berbentuk batang pada retina) telah terbentuk. Cone dan rods merupakan fotoreseptor yang aktif bekerja dan peka terhadap gelap dan terangnya cahaya. Cone bekerja ketika kondisi terang, sedangkan rods bekerja pada kondisi gelap/samar. Dengan berkembangnya adaptasi terhadap gelap dan terang maka ikan muda (juvenil) mudah dalam menangkap mangsa. Aktivitas pemangsaan yang sukses akan menunjang pertumbuhan juvenil.
beberapa larva ikan masih belum berkembang organ penglihatannya secara sempurna sehingga sedikit sekali diferensiasi dalam membedakan cahaya terang dan gelap. Pada kondisi pro larva, cahaya dibutuhkan untuk stimulus pewarnaan (pigmentasi) pada organ penglihatan dan warna tubuh, suatu peristiwa yang penting di awal pertumbuhan dan perkembangan larva.
Secara umum, lama waktu penyinaran mempengaruhi kecepatan perkembangan larva. Ada atau tidaknya cahaya dapat memberikan pengaruh aktivitas yang berbeda terhadap larva ikan. Pergerakan aktivitas larva akan mempengaruhi laju penyerapan kuning telur saat larva berkembang dari pro larva menuju post larva. Efisiensi penyerapan kuning telur yang tinggi dapat terjadi akibat dari aktivitas larva yang rendah, sehingga kuning telur lebih banyak terserap untuk pertumbuhan.
Tingkat intensitas cahaya dibutuhkan untuk mengoptimasi pertumbuhan larva. Intensitas cahaya 600 – 1300 lx dapat meningkatkan pertumbuhan pada ikan seabream, sementara larva ikan kakap berkembang secara optimal pada 600 lx. Pada spesies lain, level optimum lebih rendah seperti pada atlantic halibut, pertumbuhan terbaik pada 1-10 lx. Disamping itu juga terdapat beberapa ikan yang sensitif terhadap intensitas cahaya yang tinggi. Hal ini terlihat pada ikan Southern flounder ( paralichtis lethogstigma ) yang dicobakan pada kisaran 340 – 1600lx dan tidak memberikan pengaruh terhadap pertumbuhan dan metamorphosis, pada spesies yang sama juga ditemukan perbedaan pigementasi pada post metamorphosis larva.
Peristiwa pergerakan berkumpulnya larva ikan di bawah cahaya dapat dibedakan sebagai peristiwa langsung yakni ikan–ikan tertarik oleh cahaya lalu berkumpul dan peristiwa tak langsung yakni karena ada cahaya maka plankton dan ikan–ikan kecil berkumpul kemudian ikan–ikan kecil berkumpul kemudian ikan yang dimaksud datang berkumpul dengan tujuan feeding (mencari makan). Larva gurame lebih mudah mendapatkan pakannya saat ada cahaya yang dibuktikan dengan jumlah pakan paling banyak ditemukan dalam lambung larva gurame pada saat siang hari atau ada cahaya. Artemia bersifat fototaksis positif dan cenderung bergerombol mendekati sumber cahaya. Hal tersebut akan memudahkan larva ikan dalam menangkap artemia sebagai mangsanya.
Variasi pertumbuhan juga dapat dijelaskan melalui aktivitas larva memburu mangsa, dan sangat tergantung pada perkembangan penglihatan larva. Intensitas cahaya yang rendah dibutuhkan untuk mengembangkan aktivitas berburu secara normal. Larva sea bream lebih menyukai cahaya yang redup dengan tingkat kelangsungan hidup dan efisiensi pakan yang tinggi dibanding pada cahaya yang terang. Berdasarkan nilai rata-rata tingkat kelangsungan hidup yang dicapai maka suhu 28 oC merupakan suhu yang terbaik bagi kehidupan larva

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response of fish larvae to light intensity

Light is an external factor and ecological importance, including the color spectrum, intensity and photoperiod. Light very specific characteristics in aquatic environments and are very varied in nature. Minimum light intensity threshold required for the development and growth of fish larvae.
In the dark lighting conditions, the larvae tend to move to spread in search of prey. Thus requiring higher energy. High metabolic activity that requires large energy so that the rate of absorption of the yolk becomes faster. Larval fish on the first day after hatching did not reveal any lighting pigment in the eye and very little visual differentiation. On the third day of the retinal pigment with a storied and vision has grown cells. Then on the fifth day of the optic nerve and the cone (cone-shaped cells in the retina) has grown.
The intensity can be varied, for example between 50 and 150 lux for fish Sparus auratus. However, some species can grow and thrive in very low light intensity is as in some species of pelagic fish larvae, while snapper (Morone saxatilis). By the time the larvae generally live in estuaries with murky water. Juvenile herring Clupea harengus, swim faster and survive when moving into the dark waters.

 When the larvae transform into juveniles, the rods (rod-shaped cells in the retina) has been formed. Photoreceptor cones and rods is an active work and sensitive to dark and bright light. Cone works when light conditions, while rods work in dark conditions / vague. With the development of adaptation to darkness and light, the young fish (juvenile) is easy to catch prey. Successful predation activity will support the growth of juvenile.
some fish larvae still undeveloped organs are perfect eyesight so little differentiation to distinguish light and dark. On the pro larval condition, light is needed for stimulus coloring (pigmentation) in the organs of sight and color of the body, an important event in the early growth and development of the larvae.

 In general, longer exposure time affects the speed of larval development. The presence or absence of light can give the effect of different activities on fish larvae. The movement of larval activity will affect the rate of absorption of the yolk when larvae develop from larvae to post-larvae pro. The efficiency of yolk absorption rate may occur as a result of low larval activity, so the yolk more absorbed for growth.
The level of light intensity required to optimize the growth of the larvae. Light intensity 600 - 1300 lx can increase the growth in fish seabream, while snapper larvae develop optimally at 600 lx. In other species, the optimum level is lower as the atlantic halibut, the best growth at 1-10 lx. Besides, there are some fish that are sensitive to high light intensity. This can be seen in the Southern flounder fish (paralichtis lethogstigma) is tested in the range of 340 - 1600lx and no effect on the growth and metamorphosis, the same species are also found differences in post pigementasi larval metamorphosis

 Event gathering movement of fish larvae under the light can be distinguished as a direct event that the fish attracted by the light assembly and indirect events namely because there is no light, the plankton and small fish congregate then small fish congregate then the fish in question come together with the goal of feeding (foraging). Carp larvae easier to get their feed when there is light as evidenced by the amount of feed most commonly found in the stomach carp larvae during daytime or no light. Artemia is fototaksis positive and tend to huddle closer to the light source. This will facilitate the fish in the catch Artemia larvae as prey.
Variations in growth can also be explained by the activity of larvae prey, and very dependent on visual development of larvae. Low light intensities are needed to develop normal hunting activities. Sea bream larvae prefer dim light with a survival rate and feed efficiency were higher than those in bright light. Based on the average value of the survival rate reached the temperature of 28 ° C is the best temperature for larval life

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CAPTURE TOOLS RESOURCE CONNECTION WITH FISH (as mandated by Law No.31 / 2004)

CAPTURE TOOLS RESOURCE CONNECTION WITH FISH (as mandated by Law No.31 / 2004)
- Does not exceed the allowable catch
- The type, size and number of fishing gear and the kit in accordance with the provisions of
- Area, and time lines or fishing season in accordance with the provisions of
- Meet the requirements of standard operating procedures and fishing
- Arrests based on cultivation

 - Do not causing pollution and destruction of fish resources and the environment
- Meet the boundary conditions and the size of the minimum weight of fish caught
- Do not catch fish protected


Environmentally friendly fishing gear, is characterized 
  •  Have a high selectivity;
  •  Catches (by-catch) is low;
  •  Not damage the habitat / environment (destructive);
  • Maintain biological diversity (biodiversity);\
  • Not capturing protected species / endangered;
  • Not jeopardize the operation of the fishing gear;
  • Catches of high quality

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Fishing Gear , GILLNET

Surface gill nets is one alternative fishing gear pelagic (surface fish). Surface gill nets operated passively stretched around the waters surface facing the direction of motion of the surface of the fish ruwaya. In this way the expected type of fish that were targeted for arrest (target species) will be caught in the mesh, is the catch

 Technology manufacture and operation of surface gill nets is relatively simple, can be used by small-scale fishing effort by boat without a motor up to industrial scale using auxiliary engines arrest and navigation tools to date. The use of fishing gear that has been commonly used by the fishing community.

Giving the name of the surface gill nets are generally associated with fish catching targets (target species). One of them is the surface gill nets to catch lemuru, called gill nets lemuru surface.
 .The largest concentration of population lemuru contained in the Bali Strait, although there are in other waters but relatively small, such as in the waters of South Sulawesi, South Java and West Sumatra.

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About the spread of small crab in indonesia

Spreading the biggest crab in Indonesia are on the east coast of Sumatra, the north coast of Java and South Sulawesi. Cirebon area is one of the largest crabs are quite important in the north of Java other than Bradford, Apex and Madura. Antara News (2008) potential adult crab in Cirebon area is likely to decline and increasingly difficult to obtain the crab. Various forms of fishing gear that is both active and passive numbers increased and many small crab catch size is relatively small (100-150 individuals per kilogram) (Sumiono, 2010). Data from Cirebon (West Java) showed CPUE which tends to decrease.
 
                     Information on the level of abundance of a resource group including crab and predicted growth rate of capture at each location can be determined through CPUE trend. Rise and fall of CPUE an indication of the factors that affect the stock was mainly intensity arrest (DJPT, 2012)


                      Growth in the crab is change the size, length or weight can be within a certain time after molting. The growth was influenced by the number and size of the food available, temperature, dissolved oxygen, water quality, age and size of the organism (Fatmawati 2010). Nonji (1986) suggests that the life cycle of crab crab zoea to adults experiencing skin changes around 20 times and widths karapaksnya can reach 18 cm. Furthermore Soim (1994) suggested that based on the results of the study found the male crab carapace width has better growth compared to females.
 

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