RASIO AREA OTAK DAN ORGAN PENGLIHATAN KERAPU MACAN (Ephinephelus fuscoguttatus) HUBUNGANNYADENGAN POLAMAKAN

Otak merupakan cerminan indera-indera yang berfungsi dan berkembang pada ikan. Pemahaman tentang otak ikan akan sangat membantu dalam mempelajari adaptasi tingkah laku ikan. Ikan kerapu macan (Ephinephelus fuscoguttatus) merupakan jenis ikan yang hidup di wilayah eufotik dengan habitat kompleks, di mana ikan-ikan yang hidup pada habitat yang kompleks memiliki area otak telencephalon yang besar dan organ penglihatan yang lebih baik. Penelitian ini menggambarkan seberapa penting organ penglihatan yang dicerminkan oleh struktur otak Ephinephelus fuscoguttatus dalam hubungan dengan pola aktivitas makan. Penelitian dilakukan dengan metode eksperimen laboratorium. Ephinephelus fuscoguttatus yang digunakan memiliki panjang total rata-rata 225 sampai dengan 280 mm. Data penelitian meliputi rasio bobot otak dan data fisiologi organ penglihatan serta waktu respon makan Ephinephelus fuscoguttatus. Data diuji secara statistik dengan uji-t. Hasil penelitian menunjukkan persentase rasio area optic tectum lebih tinggi dibandingkan dengan persentase rasio area otak yang lain, yaitu 40,87 sampai dengan 49,13%. Hal tersebut, mengindikasikan bahwa indera yang berkembang adalah penglihatan. Kemampuan jarak pandang maksimum (maximum sighting distance) Ephinephelus fuscoguttatus 3,93 sampai dengan 4,74 m untuk benda berdiameter 20 mm, 4,91 sampai dengan 5,92 m untuk benda berdiameter 25 mm, serta 5,89 sampai dengan 7,11 m untuk benda berdiameter 30 mm. Pola makan Ephinephelus fuscoguttatus yang diasumsikan sebagai waktu respon makan antara kondisi siang dan malam hari tidak berbeda nyata (nilai t-hitung 1,37). Dapat diklarifikasi bahwa Ephinephelus fuscoguttatus dikelompokkan sebagai ikan karang dengan pola aktivitas makan crescupular yang menggunakan organ penglihatan untuk mencari makan. Brain is reflection of senses which is functioning and growing in fish. Understanding about fish brain would hardly assist in studying adaptation of fish behaviour. Ephinephelus fuscoguttatus is a type of fish living in euphotic zone with complex habitat. The fish that lives at complex habitat have a big brain area of telencephalon which indicate better vision organ. This research describes how the important of vision organ that expressed by brain structure of Ephinephelus fuscoguttatus related to its feeding activity pattern. Research was done using laboratory experiment method. Ephinephelus fuscoguttatus used has average total length of 225 to 280 mm. Research data covered brain weight ratio and data of visual organ and response time for feeding of Ephinephelus fuscoguttatus. Data were statistically tested using t student test. The result showed ratio area of optic tectum was higher (40.87 to 49.13%) compared to other brain area. This condition indicates that visual sense of Ephinephelus fuscoguttatus is well developed compared to other senses. The maximum sighting distance of Ephinephelus fuscoguttatus was 3.93 to 4.74 m for visual object of 20 mm diameter, 4.91 to 5.92 m for object of 25 mm and 5.89 to 7.11 m for object of 30 mm. The feeding pattern of Ephinephelus fuscoguttatus assumed as response time for feeding between noon and night time condition was not significantly (t-test was 1.37). It can be clarified that Ephinephelus fuscoguttatus grouped as reef fish with crescupular activity pattern that use their visual organ for feeding activity.

ANALISIS INDRA PENGLIHATAN IKAN KERAPU MACAN (Epinephelus fuscoguttatus) DAN HUBUNGANNYA DALAM MERESPONS UMPAN

The visual organ in fish has an important role in ensuring its survival. Fish can respond to bait or food with its visual organ. The objectives of this research are to analyse the visual performance of grouper (cone cell morphology, the visual axis, and visual acuity) and to analyse the relation between visual senses with fish behavior response to the bait. This research was conducted in the laboratory by means of the determination of fish retina histology method and behavior of fish. The morphology retina of grouper consists of a single cone and double cone which form a mosaic structure, the visual axis was identified at upper-fore with the angle of 26.8o.The visual acuity of grouper was low in index values with ranged from 0.06 to 0.07 for fish with a total length of 200 to 300 mm, the maximum sighting distance to the bait with the diameter of 20 mm size ranged from 3.93 to 4.74 m, the bait with 25 mm diameter size range from 4.91 to 5.92 and bait with a diameter of 30 mm size ranged from 5.89 to 7.11 m. The frequency of fish closed the bait distance of 30 cm was 45.83%, 25 cm was 33.33% and 20 cm was 20.83%, respectively.

Research of Instrument Erecting in the Settlement Observation when Slope Changed

The settlement observation usually adopts precision geometric leveling method, to improve the accuracy, generally requiring the value of central cross-hair to be in the range of 0.5m to 2.8m. However, it may easily exceed the range in the regions that have big value of slope. After analyzing, the conclusion is as follow: when the value of slope is certain, we can adjust the height of instrument, sighting distance and distance of slope, so as to make the value of central cross-hair in the range of our requirement. Thus make a compromise of the measurement efficiency and accuracy of measurement. When the values of slope are in the range of 10 degree to 20 degree, the critical values of sighting distance and distance of slope vary greatly. In the process of actual field measurement, combining with the slope acquisition method, taking the critical values of sighting distance and distance of slope as experience values, and it achieves a good effect.