Hokkaido University Collection of Scholarly and Academic Papers
(65.354 recursos)
HUSCAP (Hokkaido University Collection of Scholarly and Academic Papers) contains peer-reviewed journal articles, proceedings, educational resources and any kind of scholarly works of Hokkaido University.
Mostrando recursos 1 - 20 de 28
1.
A new cottid species, Icelus sekii (Perciformes: Cottoidei) from Hokkaido, Japan - Tsuruoka, Osamu; Munehara, Hiroyuki; Yabe, Mamoru
A new cottid species, Icelus sekii, is described on the basis of six specimens collected from off Rausu and Urakawa, Hokkaido Island, Japan. This species is distinguished from its congeners by the following combination of characters: supraocular and parietal spines absent; nuchal spine obscure; uppermost preopercular spine unbranched; no scales between dorsal scale row and lateral-line scale row, and no scales below lateral-line scale row; supraocular, parietal, and nuchal cirri present; five dark brown saddles dorsolaterally; anal-fin rays 13; pectoral-fin rays 15; vertebrae 12 + 24~5 = 36~7. Icelus sekii can be mature at the smallest size among the species...
2.
帆角度制御による横揺れ減揺の研究 - 芳村, 康男; 五十嵐, 佳子; 黒田, 貴子; 菊本, 充弘
Recent huge amount of CO2 discharge and the diffusion of detrimental substances by the excessive use of petroleum resources have brought the serious problem of an earth scale such as the global warming. It has been the world common subject for every work of the future to take account of the preserving natural environments. There are several solutions for taking place the petroleum energy. One of them is the wind energy. In 1980’s when the petroleum price jumped up with the twice oil crises, the use of wind power was re-examined. Many kind of modern sailing rigs and new concepts...
3.
Inducible plasticity : optimal waiting time for the development of an inducible phenotype - Nishimura, Kinya
Qeustion: How does an organism that possesses inducible plasticity determine waiting time before the development of a secondary phenotype is suitable?
Model: Maximization of the fitness currency, the survival possibility times the expected amount of remaining energy at terminal time, with respect to waiting time before development of a secondary phenotype.
Key assumptions: If the individual develops the inducible secondary phenotype in the secondary environment, death rate is reduced. The development and maintenance of the inducible phenotype incurs a cost.
Results: The optimal waiting tiem should be longer under the following conditions: when the inducible phenotype has low effectiveness in...
4.
Validity and visualization of a numerical model used to determine dynamic configurations of fishing nets - Suzuki, Katsuya; Takagi, Tsutomu; Shimizu, Takashi; Hiraishi, Tomonori; Yamamoto, Katsutaro; Nashimoto, Katsuaki
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...
5.
Video analysis of fish schooling behavior in finite space using a mathematical model - Suzuki, Katsuya; Takagi, Tsutomu; Hiraishi, Tomonori
The schooling behavior of the fish Parapristipoma trilineatum (chicken grunt) was examined for a range of school sizes
in a water tank containing a central columnar structure using a mathematical model of fish schooling behavior that was
modified from that of Sannomiya and Matuda. The two-dimensional motion of individuals was captured on digital video over
about 10 min, and these time-series data were used to tune the model to the experimental conditions. The model parameters
were then used to evaluate schooling behavior quantitatively. Comparing force magnitudes between experimental conditions
revealed that propulsive force was less in a tank without the central structure than in a...
6.
Increase of inbreeding by stocking on wild population assessed by using individual-based life history model - Oota, Takeyuki; Matsuishi, Takashi
We assessed the genetic impact of stocking on natural populations by using individual-based
life-cycle models. We constructed models that used include density-dependent mortality at the early
life stage, natural mortality, fishing mortality, and the number of released fish. We varied these
variables by using random numbers. We focused on the genetic impact of the number of released
fish, the number of parent fish producing seedlings that were released, the sex ratio of the parent
fish, fishing mortality, and the methods to select the parents of the seedlings. When brood stock size
in hatchery is 5 male and 5 female, is...
7.
Weight-based yield per recruitment and spawning-biomass per recruitment analyses of Pacific cod Gadus macrocephalus off the Pacific coast of southern Hokkaido, Japan - Ueda, Yuji; Matsuishi, Takashi
The present study assessed the stock state of Pacific cod Gadus macrocephalus caught off the coast of southern Hokkaido, Japan. Weight-based yield per recruitment (YPR) and spawning-biomass per recruitment (SPR) analyses were used for this assessment. The current fishing mortality (average from 1998 to 2000) was 0.65 and weight at first capture was 0.5 kg bodyweight. Under these fishing pressures, the YPR of Pacific cod in southern Hokkaido was 1.06 kg/recruitment and percentage of SPR (%SPR) was 6.9%. The %SPR was lower than the critical limit at 20%SPR. The main reason that values of both YPR and %SPR were not...
8.
Estimation of Gillnet Selectivity Curve by Maximum - Fujimori, Yasuzumi; Tokai, Tadashi
A maximum likelihood method of estimating gillnet selectivity when
the data are obtained by gillnet fleets consisting of several nets of differing
mesh size is presented in this paper. The SELECT model is expanded by
application of the relative length (i.e. the ratio of fish length to mesh size)
to obtain a master curve of gillnet selectivity. Four kinds of functional
model, normal, lognormal, skew-normal and bi-normal are fitted to the data.
In addition, two cases where the relative fishing intensity is either
estimated or fixed by catch effort are compared. The bi-normal model has
the lower model deviance regardless...
9.
The influence of warp length on trawl dimension and catch of walleye pollock Theragra chalcogramma in a bottom trawl survey - Fujimori, Yasuzumi; Chiba, Kenji; Oshima, Tatsuki; Miyashita, Kazushi; Honda, Satoshi
We examined variation in trawl dimension, bottom contact, and catch with differing warp
lengths during walleye pollock surveys conducted by the Fisheries Research Agency. The
ratio of warp length to fishing depth (scope ratio) was set at 2.5, 3.0 and 3.5 at depths of 110 m.
At a 2.5 scope ratio, the net mouth shape and footgear contact fluctuated, as the trawl door did
not contact the bottom. Footgear contact was complete when the scope ratio was 3.0 or more.
Walleye pollock, sculpins, and flatfishes were the main catch in all tows, and the catch
increased with scope ratio. There...
10.
Design of a Small Fisheries Research Vessel with Low Level of Underwater-Radiated Noise - Yoshimura, Yasuo; Koyanagi, Yasunari
It is important for a fisheries research vessel to reduce the underwater-radiated noise. In 1995, the International
Council for the Exploration of the Sea (ICES) firstly recommended the maximum noise level for research vessels
to ensure the acoustic research works and to prevent the fish reaction against the noise 1). Since then, it has been
the world standard for the design of fisheries research vessels. For a small size vessel, however, it is very difficult
to achieve the recommendations because of not enough space or capacity to make sound insulations. Moreover,
the Froude number (Fn) of such small vessels tends to be higher than that...
14.
Spatial distribution and feeding habits of the shrimp Crangon uritai as a predator on larval and juvenile marbled sole Pleuronectes yokohamae - NAKAYA, Mitsuhiro; TAKATSU, Tetsuya; NAKAGAMI, Masayasu; JOH, Mikimasa; TAKAHASHI, Toyomi
To examine predation on larval and juvenile Pleuronectes yokohamae by Crangon uritai, the spatial distribution and feeding habits of C. uritai were studied. Crangon uritai fed on various prey, including P. yokohamae. Density-dependent predation on juvenile Crangon spp., larval and juvenile gobiid fish Chaenogobius heptacanthus, mysids, and gammarids was observed. The abundance of alternative prey might, therefore, play an important role in reducing the pressure of predation on P. yokohamae. In each year, C. uritai migrated from depths of 10 m in March to depths of 3 m in May. There was a significant negative correlation between the weighted mean...
15.
Effect of aging time on the availability of freshly precipitated ferric hydroxide to coastal marine diatoms - Yoshida, Masahiko; Kuma, Kenshi; Iwade, Shouei; Isoda, Yutaka; Takata, Hyoe; Yamada, Masumi
Cell growth and iron uptake of the coastal marine diatoms Chaetoceros sociale and Thalassiosira weissflogii were studied in the presence of short-aged amorphous ferric hydroxide (am-Fe(III)) media. These were prepared by aging for 1 day, 3 days, and 3 weeks after adding a small amount of ferric iron acidic stock solution to autoclaved filtered seawater and were experimentally measured in culture experiments at 10 degrees C for C. sociale and 20 degrees C for T. weissflogii. The order of cell yields for both species was: 1-day aged am-Fe(III) > 3-day aged am-Fe(III) >> 3-week aged am-Fe(III) media. The iron uptake...
16.
Biogeochemical fluxes through mesozooplankton - Buitenhuis, Erik; Le Quere, Corinne; Aumont, Olivier; Beaugrand, Gregory; Bunker, Adrian; Hirst, Andrew; Ikeda, Tsutomu; O'Brien, Todd; Piontkovski, Sergey; Straile, Dietmar
Mesozooplankton are significant consumers of phytoplankton, and have a significant impact on the oceanic biogeochemical cycles of carbon and other elements. Their contribution to vertical particle flux is much larger than that of microzooplankton, yet most global biogeochemical models have lumped these two plankton functional types together. In this paper we bring together several newly available data syntheses on observed mesozooplankton concentration and the biogeochemical fluxes they mediate, and perform data synthesis on flux rates for which no synthesis was available. We update the equations of a global biogeochemical model with an explicit representation of mesozooplankton (PISCES). We use the...
17.
バルジによる改造漁船船型の操縦性能 - 芳村, 康男; 馬, 寧; 鈴木, 四郎; 梶原, 善之
Fishing boats suffer from much capsizing as compared with other vessels. It may be pointed out that the stability of fishing boats tend to be poor as the bases of the severe operations and the poor management of loading condition as well as the problem with the restrictions of principal dimensions of ship. According to the recent capsizing of the trawler “Ryuho-maru V”, Ministry of Land, Infrastructure and Transport of Japan forced to check the stability of existing fishing boats and to improve the stability if not enough.
As for the improvement of the stability, the fitting of a bulge on...
18.
バルジによる改造漁船船型の波浪中運動の基本特性 - 馬, 寧; 芳村, 康男; 木村, 暢夫; 鈴木, 四郎; 山越, 康行
In order to improve the stability and to increase the working area for fishing vessel, bulges are often added on ship sides from underwater part up to upper deck. From the view point of seakeeping quality, it is important to clarify the effect of bulges on ship dynamic response as well as static stability. A fisheries research vessel “Ushio-maru” has been rebuilt (elongated and bulges fitted) recently. In this paper, we present the results of investigation into its stability improvement and study on the influence of bulge on its motion in waves by model experiments and theoretical calculations. It was...
19.
バルジによる漁船の船型改良について - 川島, 敏彦; 芳村, 康男; 鈴木, 四郎; 大本, 耕司
Fishing boats have several restrictions on their machinery arrangements and space utility on deck. For the improvement of the stability and the deck utility, the fitting of a bulge on sidewall of the vessel is one of the solutions. However, the bulge generally makes a significant increase of hull resistance and loss of speed. At the principal design stage of the elongation of the fisheries research ship “Ushio-maru”, the University of
Hokkaido, the authors examined the suitable form of the bulge to improve the stability without increase of the hull resistance. For this purpose, systematic calculations of wave making resistance by...
20.
Evolution of the maturation rate collapses competitive coexistence - Mougi, Akihiko; Nishimura, Kinya
Most theoretical studies on character displacement and the coexistence of competing species have focused attention on the evolution of competitive traits driven by inter-specific competition. We investigated the evolution of the maturation rate which is not directly related to competition and trades off with the birth rate and how it influences competitive outcomes. Evolution may result in the superior competitor becoming extinct if, initially, the inferior competitor has a lower, and the superior one a higher, maturation rate at the coexistence equilibrium. This counterintuitive result is explained by an explosive increase in the adult population of the inferior competitor as...
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