The systematic sampling for inferring the survey indices of Korean groundfish stocks

( Saang-yoon Hyun ),( Young Il Seo ) 한국수산과학회(구 한국수산학회) 2018 Fisheries and Aquatic Sciences Vol.21 No.3

The Korean bottom trawl survey has been deployed on a regular basis for about the last decade as part of groundfish stock assessments. The regularity indicates that they sample groundfish once per grid cell whose sides are half of one latitude and that of one longitude, respectively, and whose inside is furthermore divided into nine nested grids. Unless they have a special reason (e.g., running into a rocky bottom), their sample location is at the center grid of the nine nested grids. Given data collected by the survey, we intended to show how to appropriately estimate not only the survey index of a fish stock but also its uncertainty. For the regularity reason, we applied the systematic sampling theory for the above purposes and compared its results with a reference, which was based on the simple random sampling. When using the survey data about 11 fish stocks, collected by the spring and fall surveys in 2014, the survey indices of those stocks estimated under the systematic sampling were overall more precise than those under the simple random sampling. In estimates of the survey indices in number, the standard errors of those estimates under the systematic sampling were reduced from those under the simple random sampling by 0.23~27.44%, while in estimates of the survey indices in weight, they decreased by 0.04~31.97%. In bias of the estimates, the systematic sampling was the same as the simple random sampling. Our paper is first in formally showing how to apply the systematic sampling theory to the actual data collected by the Korean bottom trawl surveys.

The systematic sampling for inferring the survey indices of Korean groundfish stocks

Hyun, Saang-Yoon,Seo, Young IL The Korean Society of Fisheries and Aquatic Scienc 2018 Fisheries and Aquatic Sciences Vol.21 No.8

The Korean bottom trawl survey has been deployed on a regular basis for about the last decade as part of groundfish stock assessments. The regularity indicates that they sample groundfish once per grid cell whose sides are half of one latitude and that of one longitude, respectively, and whose inside is furthermore divided into nine nested grids. Unless they have a special reason (e.g., running into a rocky bottom), their sample location is at the center grid of the nine nested grids. Given data collected by the survey, we intended to show how to appropriately estimate not only the survey index of a fish stock but also its uncertainty. For the regularity reason, we applied the systematic sampling theory for the above purposes and compared its results with a reference, which was based on the simple random sampling. When using the survey data about 11 fish stocks, collected by the spring and fall surveys in 2014, the survey indices of those stocks estimated under the systematic sampling were overall more precise than those under the simple random sampling. In estimates of the survey indices in number, the standard errors of those estimates under the systematic sampling were reduced from those under the simple random sampling by 0.23~27.44%, while in estimates of the survey indices in weight, they decreased by 0.04~31.97%. In bias of the estimates, the systematic sampling was the same as the simple random sampling. Our paper is first in formally showing how to apply the systematic sampling theory to the actual data collected by the Korean bottom trawl surveys.

The systematic sampling for inferring the survey indices of Korean groundfish stocks

HYUN SAANG YOON,이성일 한국수산과학회 2018 Fisheries and Aquatic Sciences Vol.21 No.3

The Korean bottom trawl survey has been deployed on a regular basis for about the last decade as part of groundfish stock assessments. The regularity indicates that they sample groundfish once per grid cell whose sides are half of one latitude and that of one longitude, respectively, and whose inside is furthermore divided into nine nested grids. Unless they have a special reason (e.g., running into a rocky bottom), their sample location is at the center grid of the nine nested grids. Given data collected by the survey, we intended to show how to appropriately estimate not only the survey index of a fish stock but also its uncertainty. For the regularity reason, we applied the systematic sampling theory for the above purposes and compared its results with a reference, which was based on the simple random sampling. When using the survey data about 11 fish stocks, collected by the spring and fall surveys in 2014, the survey indices of those stocks estimated under the systematic sampling were overall more precise than those under the simple random sampling. In estimates of the survey indices in number, the standard errors of those estimates under the systematic sampling were reduced from those under the simple random sampling by 0.23~27.44%, while in estimates of the survey indices in weight, they decreased by 0.04~31.97%. In bias of the estimates, the systematic sampling was the same as the simple random sampling. Our paper is first in formally showing how to apply the systematic sampling theory to the actual data collected by the Korean bottom trawl surveys.

Inseason forecast of sockeye salmon return timing to Bristol Bay, Alaska

HYUN, Saang-Yoon 한국수산자원학회 2002 한국수산자원학회지 Vol.5 No.-

The annual variability in return timg of the Bristol Bay sockeye salmon (Oncorhynchus nerka) is one of the main factors that make an accurate forecast of the homing fish abundance difficult. Using the catch per unit effort data of the Port Moller test fishery, I developed methods of detecting the return timing five or seven days before the salmon reach the inshore bay. The temporal pattern in the CPUE at Port Moller explained about 59% of the variation in return timing in the fishing districts.

A Length-based Analysis of Recruitment Variability in the Korean Pollock Population under Data-limited Conditions

김규한,HYUN SAANG YOON 한국해양과학기술원 2018 Ocean science journal Vol.53 No.3

The walleye pollock (Gadus chalcogrammus) population in Korean waters had thrived until the mid-1980s, but this fish population has been depleted since the late 1990s. Limited data and lack of ecological research about the population prevented us from revealing the mechanism or material cause that resulted in the population’s collapse. Instead, we intended to examine possible hypotheses for the collapse, and built a statistical linear model, where juvenile fish, adult fish, and environmental factors were explored as variables. Because actual data on fish ages were not available, we estimated age compositions of the fish sample, applying the length-frequency analysis suggested by Schnute and Fournier (1980) to data on their lengths. Then we used the estimates of age compositions to determine adequate time lags between juvenile and adult stages in the statistical linear model. The selected final model suggested that the depletion of the fish population was associated with changes in water temperatures during April, June, and October and with adult abundance, but was not with the other species (e.g., sandfish (Arctoscopus japonicus) and flatfishes (Pleuronectidae sp.)) considered in the model. We further interpreted the results from ecological perspectives, referring to previous studies and ecological hypotheses.

Modification of Quinn’s length-based model for Korean chub mackerel (Scomber japonicus) population

Jinwoo Gim,Saang-Yoon Hyun,Jae Bong Lee 한국수산과학회 양식분과 2019 한국수산과학회 양식분과 학술대회 Vol.2019 No.5

A Bayesian sate-space production model for Korean chub mackerel (Scomber japonicas) stock

Yuti Jung,Saang-Yoon Hyun,Young Il Seo 한국수산과학회 양식분과 2019 한국수산과학회 양식분과 학술대회 Vol.2019 No.5

확률론적 연령구조모델을 이용한 한국 고등어(Scomber japonicus) 어획 강도

김진우 ( Jinwoo Gim ),현상윤 ( Saang-yoon Hyun ),이재봉 ( Jae Bong Lee ) 한국수산과학회(구 한국수산학회) 2020 한국수산과학회지 Vol.53 No.6

Achieving optimal sustainable yields (i.e., avoiding overfishing and maximizing fishery harvest at the same time) is one of the main objectives in fisheries management. Generally, management reference points (MRPs) such as fishing mortalities (Fmsy, F0.1, Fx%) have been suggested for the purpose. In this study, we intended to suggest MRPs for Korea chub mackerel Scomber japonicus stock, using a stochastic catch-at-age model (SCAA) and evaluate whether the current fishing intensity on the stock is appropriate. We used length frequency and catch-per-unit-effort data on the Korea chub mackerel stock collected from the large purse-seine fishery, and yields landed by all fisheries from years 2000 - 2019. We calculated yield per recruit and spawning potential ratio, and projected spawning stock biomass (SSB) under different fishing mortality, assuming annual recruitments were solely controlled by environmental effects (i.e., steepness of 1.0). Some of our major findings and suggestions were that the overfishing threshold would be F46%; i.e., the fishing mortality in the terminal year, 2019 was 0.257/year, which corresponded to F46%.

제주연안에 서식하는 오분자기, Haliotis diversicolor aquatilis의 생식주기

김성훈,이치훈,송영보,김병엽,HYUN SAANG YOON,이영돈 한국발생생물학회 2012 발생과 생식 Vol.16 No.2

제주도 성산 연안 지역에 서식하는 오분자기의 생식주기를 조사하기 위하여 2006년 5월부터 2007년 4월까지채집된 개체를 대상으로 생식소지수와 생식세포 발달단계, 황색 과립세포 출현양상과 생식상피의 형태변화를 조사하였다. 생식소지수(GI)의 월별 변화는 암컷과 수컷 개체 모두 유사한 경향을 보였다. 암컷 GI는 2006년 5월 21.63±2.42에서6~8월 55.38±11.73으로 최대값을 보였고, 9월 27.75±4.76으로 감소하였다가 10월 51.36±7.47 증가한 후 2007년 4월까지낮은 값(7.65±0.85)을 유지하였다. 오분자기의 생식주기는 생식세포 발달 단계에 따라 연속적인 6단계로 구분하였다. 암컷은 분열증식기(2월과 5월), 성장기(2월~5월), 성숙기(4월~7월), 부분산란기(5월~11월), 퇴행기(10월~12월) 그리고 회복기(9월~10월, 12월~2월) 등으로 구분할 수 있었다. 수컷은 분열증식기(2월과 5월), 성장기(3월~5월), 성숙기(4월~7월),방정기(6월~11월), 퇴행기(11월~2월) 그리고 회복기(9월~2월) 등으로 구분할 수 있었다. 생식소내 황색과립세포는 성숙및 산란기보다 분열증식기, 성장기, 퇴행기, 회복기에 많이 관찰되었다. 오분자기 GI 및 생식소의 조직상 관찰 결과, 암컷은 5월부터, 수컷은 6월부터 일부 개체가 부분산란 및 방정을 시작하여 8~9월에 1차 산란을 한 후 10~11월에 2차 산란에 가입하는 경향을 보여 일 년에 2회 이상의 산란시기를 갖는 다회 산란특성을 보였다

한반도 연근해 저층 트롤 조사 자료에 표본론을 적용한 개체군의 상대적 크기 추정

이효태,현상윤,Lee, Hyotae,Hyun, Saang-Yoon 한국수산과학회 2017 한국수산과학회지 Vol.50 No.5

The Korean National Institute of Fisheries Science (NIFS) has biannually (spring and fall, respectively) deployed a bottom trawl survey along the coastal areas for last decade, taking samples on a regular basis (i.e., a systematic sampling). Despite the availability of the survey data, NIFS has not yet officially reported the estimates of the groundfish population sizes as well as has not evaluated uncertainty of the estimates. The objectives of our study were to infer the relative size of a fish population, applying two different sampling techniques (namely simple and stratified sampling) with different observation units to the NIFS survey data, and to compare those two techniques in bias and precision. For demonstration purposes, we used data on Pacific cod (Gadus macrocephalus) collected by the 2011-2015 surveys, and the results of simple and stratified sampling showed that the point estimates and precision varied by observation unit as well as the sampling technique.