–  The continuous observation of salmon behaviour in some wild environments can be extremely difficult. We recorded spawning behaviour of female chum salmon (Oncorhynchus keta) in the field simultaneously using visual observation and fish‐borne data loggers with two‐axis accelerometer sensors. Using only acceleration records, behaviours were successfully classified into the eight well‐known components of spawning behaviour: swimming, nosing, exploratory digging, nest digging, probing, oviposition, covering and post‐spawning digging. To understand how the female chum salmon modulates spawning behaviours in relation to changes in environmental conditions, we compared the behaviours of salmon during normal flow of clear water to those of salmon during the heavy flow of turbid water after a storm. Salmon in the normal flow showed all eight behaviours, whereas salmon in the heavy flow showed only three behaviours: swimming, nosing and exploratory digging. The proportion of time spent on swimming was greater in the heavy flow than in the normal flow (mean of 98.47% vs. 92.84%). Moreover, the proportion of tail beating in swimming was greater in the heavy flow (77.86%) than in the normal flow (15.63%). Our results indicate that the behaviour of female chum salmon was strongly affected by the heavy flow of turbid water after a storm. The recording of accelerations is a promising method for clarifying the spawning behaviour of salmonids in the wild where continuous visual observation is too difficult.

The tail beat and activity behavior of four captive Japanese flounder Paralichthys olivaceus, were monitored with acceleration data‐loggers while the fish swam in an aquarium. Depth, swimming speeds and two‐axis acceleration data were collected continuously for approximately 20 h per fish. Simultaneously, the swimming behaviors of the fish were filmed at different angles. Using the specific characteristic of the acceleration profiles, in tandem with other types of data (e.g. speed and depth), four behavioral patterns could be distinguished: (i) ‘active’ swimming; (ii) burying patterns; (iii) ‘inactive’ gliding; and (iv) lying on the bottom. Tail beat frequency ranged from 1.65 ± 0.47 to 2.04 ± 0.25 Hz (mean ± SD; n = 4). Using the relationship between tail beat frequency and swimming speed, the ‘preferred’ swimming speed of the fish was estimated to be between 0.6 and 1.2 body lengths (BL)/s. Additionally, fish rarely swam faster than 1.2 BL/s. This study shows that the acceleration data‐loggers represent a useful and reliable system for accurately recording the tail beat of free‐ranging fish and estimating flatfish behavior.

:  The aim of the present study was to develop a numerical calculation method to simulate the three‐dimensional dynamic behavior of fishing nets. In a previous study, we presented a formulation to calculate net configurations. In this method, fishing nets were modeled as a group of lumped mass points interconnected with springs that have no mass. To verify the validity of calculation results using a computational model, we performed the flume tank experiments with a rectangular net and compared results with those of the numerical simulation of experiments. Using our method, numerical calculations for a rectangular net in a steady flow can provide accurate results. The calculated load and tension force distribution of the flat net were generally in accordance with the results of the flume tank experiments. This study shows that our method is valid for the simulation of fishing nets; furthermore, we have resolved earlier problems that were associated with this model.

The auditory thresholds for 10 specimens of the marbled sole Pleuronectes yokohamae were deter mined by heartbeat conditioning using pure tone stimuli of 9 frequencies from 60 to 1,000Hz, which were coupled with an electric shock. The marbled sole could hear sound in the frequency range from 60 to 1,000Hz, and the lowest threshold was 92.5dB re 1ƒÊPa at 100Hz. Hearing ability declined rapidly with increasing frequency above 300Hz, but little difference occurred in hearing ability be tween 400 and 500Hz. The results show that the auditory thresholds of marbled sole are higher and its sensitive frequency range is narrower than that for fish that have swimbladder.