Kuo-Tien Lee

A Fuzzy Logic Method for Collision Avoidance in Vessel Traffic Service

Currently Vessel Traffic Service (VTS) does not have enough technical capability to monitor a crowded surveillance area to maintain safety. Without an efficient alerting system, many marine accidents have occurred due to operator oversight. In this article, a new fuzzy logic method is proposed to add vessel collision avoidance capability to VTS/AIS systems for all potential collision ships in the surveillance area. Starting from the VTS standpoint and integrating AIS data into the Marine Geographic Information System (MGIS) as a platform, the calculations of ship domain and ship inertial force are utilized to generate models of a guarding ring and danger index. By this means, a precise prediction of collision time and position can be achieved using a marine GIS spatial analyst module. The proposed method is able to enhance the VTS operators decision-making abilities by providing a collision avoidance alerting system.

Multisatellite observation on upwelling after the passage of Typhoon Hai‐Tang in the southern East China Sea

[1]xa0The serial remote sensing based imageries clearly revealed large scale of upwelling within large regional enhancement of chlorophyll-a (Chl-a) concentration in the southern East China Sea (ECS) after the passage of super typhoon Hai-Tang in July 2005. After the typhoon on 22 July, the upwelling area ( 3.0 mg/m3 appeared in the shelf region, where the high Chl-a pattern matched the upwelling in terms of location and time. On the other hand, a large offshore SST cooling was also observed mainly to the right of typhoon track on 20 July, it lasted in a period of 2–3 days. This paper provides clear and high-resolution evidence that typhoon significant increased upwelling and Chl-a concentration in the southern ECS.

Fast computation of sample entropy and approximate entropy in biomedicine

Both sample entropy and approximate entropy are measurements of complexity. The two methods have received a great deal of attention in the last few years, and have been successfully verified and applied to biomedical applications and many others. However, the algorithms proposed in the literature require O(N(2)) execution time, which is not fast enough for online applications and for applications with long data sets. To accelerate computation, the authors of the present paper have developed a new algorithm that reduces the computational time to O(N(3/2))) using O(N) storage. As biomedical data are often measured with integer-type data, the computation time can be further reduced to O(N) using O(N) storage. The execution times of the experimental results with ECG, EEG, RR, and DNA signals show a significant improvement of more than 100 times when compared with the conventional O(N(2)) method for N=80,000 (N=length of the signal). Furthermore, an adaptive version of the new algorithm has been developed to speed up the computation for short data length. Experimental results show an improvement of more than 10 times when compared with the conventional method for N>4000.

Species identification of fish shoals from echograms by an echo-signal image processing system

Abstract Echograms of 229 fish shoals, including 35 skipjack, 43 round scad, 49 horse mackerel, 60 anchovy and 42 larval fish, were collected in the coastal waters of northeast Taiwan from 1991 to 1993. Using these data, the echo-signal image processing system (EIPS) was developed for species identification of echograms of fish shoals. The system consisted of programs for digital image transformation, digital image processing, measurement and computation of shoal descriptors, and discriminant functions for species identification. Also, principal component analysis, variable clustering analysis and stepwise discriminant analysis were conducted to determine the relationships among the descriptors. The important shoal descriptors for species identification were those related to external structure of the shoals (area, perimeter, height, width, axis length, circularity, rectangularity and number of pixels) and to internal structure of the shoals (mean value, standard deviation, skewness and curtosis of signal amplitude). The former explained more variances than the latter. The accuracy of species identification by the system was 98% for round scad, 97% for anchovy, 94% for skipjack, 91% for larval fish, and 67% for horse mackerel.

On the relationship between El Niño/Southern oscillation and South Pacific albacore

The influence of El Nino/Southern oscillation (ENSO) episodes on South Pacific albacore (Thunnus alalunga) is analyzed using historical catch per unit effort (CPUE) data collected from the Taiwanese distant-water longline fishing fleet, Southern oscillation indices and large scale measurements of seawater temperature. Two effects were identified from a time series analysis: (1) relatively low CPUE followed the onset of ENSO episodes with 8 and 4 yr time lag in fishing grounds between 10°S and 30°S and south of 30°S, respectively; and (2) towards the beginning of ENSO episodes CPUE was slightly higher in fishing grounds between the equator and 10°S. The time lag of the first effect corresponds to the time intervals that would be expected before the recruitment for the fish spawned during ENSO episodes. The second effect is interpreted as a result of the anomalous temperature structure of the seawater. The rise of the mixed layer depth (MLD) in the equatorial region as well as the narrowing volume of water comprising the albacores temperature preference in the subtropical region would both be expected to lead to a (slight) increase in the hook rate of albacore in the two regions.

Effects of fishing effort on stock size and catch of larval anchovy in coastal waters of southwestern Taiwan

Abstract Using monthly catch, fishing effort and catch per unit of effort (CPUE) data, the effects of fishing effort on stock size and catch were evaluated for the larval anchovy fishery in the coastal waters of southwestern Taiwan from 1980 to 1992. A analysis of the autocorrelation function of the CPUE time series (univariate ARIMA model) and the cross-correlation function of the prewhitened time series between CPUE and fishing effort (transfer function noise model) showed that neither stock size nor fishing effort in a fishing season affected stock size the following fishing season. Also, the synchronization of fishing effort with stock size and catch suggested that the fishery is operated efficiently. When the surplus production model was used, there was a significant negative correlation between CPUE and fishing effort. This is more likely due to an underestimation of CPUE caused by the increase in fishing effort rather than an actual decrease in stock size.

Environmental factors associated with the formation of larval anchovy fishing grounds in the coastal waters of southwest Taiwan

Daily commercial catches, school sizes and school densities of larval anchovy, and oceanographic and meteorological variables for the fishing seasons (January to June) from 1988 to 1990 were analyzed by means of principal component analysis to identify causative factors for the aggregation and abundance of larval anchovy, which make up the grounds in the coastal waters of southwest Taiwan. The results suggested that the primary factors associated with the formation of fishing grounds were surface water temperature that related to the occurrence of Engraulis japonicus, surface water salinity that was affected by influex of offshore water and river discharge, and phosphate content and solar radiation that affected plankton production.

The larval anchovy (Engraulis japonicus) fishery in relation to the environmental factors in coastal waters of Fangliao, Taiwan

Abstract Daily commercial catches, school densities and school sizes of larval anchovy ( Engraulis japonicus ), and oceanographic and meteorological variables for the spring fishing season (January to June) from 1988 to 1990 were analyzed by multiple regression analysis to identify factors influencing the aggregation and abundance of larval anchovy in the coastal waters of Fangliao, Taiwan. The results suggest the important factors were school density, that related to the mean body length of the larvae, surface water temperature, that determined the occurrence of Engraulis japonicus , surface water salinity, that was affected by river discharge and spring and neap tides, and the phosphate content and solar radiation, that affected plankton production.

Effects of climate variability and climate change on the fishing conditions for grey mullet (Mugil cephalus

Grey mullet (Mugil cephalus L.) is one of the most important commercial species of fish in the coastal fisheries of Taiwan. In this study, we analyzed the long-term (1967–2009) records of grey mullet catch per unit effort (CPUE) in the Taiwan Strait (TS) to investigate the influences of climatic indices on the annual catch of grey mullet at multiple timescales. A wavelet analysis revealed that variations in climatic indices, namely the Pacific Decadal Oscillation (PDO), the Oceanic Niño Index, and sea surface temperatures (SSTs) might have affected the abundance and migration behavior of grey mullet in the TS in winter. The CPUE of grey mullet showed significant high correspondence with the annual PDO index (R2u2009=0.82, pu2009<0.01). The results suggested that the PDO affects the migration of grey mullet, but that increases in SSTs are a more important influence on the decreased catches of grey mullet after 1980. Mean SSTs increased 1.01xa0°C at the Chang-Yuen Rise in the TS from 1984 to 2009. The 20xa0°C isotherms in the TS in the winter also shifted from 23–24°N in 1958–1978 to north of 25°N after 1998. The fishing grounds of grey mullet also shifted to the north following changes in the 20xa0°C isotherm in the TS.

Behavioural responses of larval anchovy schools herded within large-mesh wings of trawl net

Abstract Thirteen hydroacoustic surveys were conducted to study the behavioural responses of larval anchovy schools ( Engraulis japonicus, Encrasicholina punctifer , and E. heteroloba ) toward large-mesh trawl net wings (stretch meshes of 8 cm to 162 cm) during fishing in coastal waters of southwestern Taiwan. The wings served as an effective herding gear for the larvae. The herding efficiency was size dependent and increased with increase of larval body size. Between the wings, schools of larger larvae aggregated farther away from the wings toward the centre than those of smaller larvae, and had lower escapement through the meshes.