The maximum catch per unit of gillnet (unit had about 131, 000 meshes) for Wakasagi (pondsmelt) Hypomesus transpcificus nipponensis was estimated from the catch data of experimental fishings. Each fishing operation was designed to have different soaking time of the gear with the repetition of haulinjg, in which the distribution of the enmeshed fish was recorded before the gear was reset into the water with the catch intact.
The distance between each enmeshed fish was measured from the record in each haul and the catch-loss which dropped off from the mesh was checked comparing with the position of each enmeshed fish in the former hauling.
The results obtained here are summarized as follows;
1) Variation of catch with different soaking time from one hour to four hours showed the realized maximum number as more than 150 individuals.
2) The ratio of loss number to the enmeshed fish amounted to over 20%, and higher percentage of this ratio was observed within one hour after the fish was enmeshed.
3) The influence of the enmeshed fish seemed to decrease the efficiency of the neighbouring meshes within 7cm.
4) Potential catch per unit in this type of gillnet was estimated to be approximately 1, 000 individuals.

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Lobsters are commonly caught by bottom-set gillnets in Japan, and the height of the net is rather low compared with other bottom-set gillnets.
Let N denote the number of lobsters caught by a certain mesh of a gillnet which is h in height above the sea bottom. Here the value of h is determined by h=l(n-1/2)√2s-s², l being the mesh size of the gillnet used, h the number of mesh counted from the foot rope towards the head rope and s the coefficient of hanging given to the net.
The relationships between h and N obtained from the experiment were as follows:
The maximum catch of lobsters was obtained at the 3rd mesh which is about 19 cm high above the sea bottom and the relationships between h and N were LogN_(%)=??.88+0.09 h and either Log N_(%)=2.60-0.045 h or Log N_(%)=2.78-0.055 h in accordance with changes in the value of h and the month experimented.
The maximum catch of top-shells was observed at the height of about 58 cm.
Although the catch of the lobster was strongly affected by the phase of moon, that of the top-shell was not influenced by the moon at all.

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Using an automatic sensing instrument developed for observing the behaviour of crawling creatures, the authors investigated the influence of different underwater light intensities on the behaviour of Japanese spiny lobster, Panulirus japonicus, under light and dark alternating cycles of 24 hours. When the downward irradiance during light period was 3.3×10²lx and that during the dark period was more than 5.2×10^-3lx, the spiny lobster's behaviour during the dark period were largely disturbed: locomotor frequency was less than 1/4 in comparison with that under 0lx conditions in the dark period. Such a response was continuously maintained during the experimental period of 31 days. The locomotor frequency did not decrease at all when the downward irradiance during the dark period was less than 2.3×10^-5lx. On the other hand, there was hardly any difference in locomotor frequency during the dark period when the downward irradiance during the light period was of 3.5×10^-2lx and 3.3×10²lx.
In consequence, it was understood that Japanese spiny lobster locomotive behavior was considerably suppressed whenever underwater brightness increased even slightly during the nighttime.

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雄イセエビの摂餌行動および摂餌量を284日間連続測定した。これらの値の変化はイセエビの脱皮や水温変化によって著しく制約された。イセエビは,夏と秋の脱皮約1ヶ月前より摂餌量が減少し始め,脱皮直前には5～17日間摂餌せず,脱皮後には2～26日間以上摂餌しなかった。夏の脱皮後は摂餌量が急激に増加した。イセエビが摂餌した最低水温は11.8℃であった。イセエビの摂餌量は水温の上昇とともに顕著な増加傾向がみられたが,水温が28℃以上となると減少傾向に転じた。

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