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.

개체군 체장자료를 이용한 연령조성 추정

김규한 ( Kyuhan Kim ),현상윤 ( Saang-yoon Hyun ),서영일 ( Young Il Seo ) 한국수산과학회(구 한국수산학회) 2018 한국수산과학회지 Vol.51 No.1

Fish ages are critical information in fish stock assessments because they are required for age-structure models such as virtual population analysis and stochastic catch-at-age models, whose outputs include recruitment strengths, a spawning stock size (abundance or biomass), and the projection of a fish population size in future. However, most countries other than the developed countries have not identified ages of fish caught by fisheries or surveys in a consistent manner for a long time (e.g.,>20 years). Instead, data about fish body sizes (e.g., lengths) have been well available because of ease of measurement. To infer age compositions of fish in a target group using fish length data, we intended to improve the length frequency analysis (LFA), which Schnute and Fournier had introduced in 1980. Our study was different in two ways from the Schnute and Fournier’s method. First we calculated not only point estimates of age compositions but also the uncertainty in those estimates. Second, we modified LFA based on the von Bertalanffy growth model (vB-based model) to allow both individual-to-individual and cohort-to-cohort variability in estimates of parameters in the vB-based model. For illustration, we used data about lengths of Korean mackerel Scomber japonicas caught by purse-seine fisheries from 2000-2016.

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%.

한국 연근해 어업에서 수집되는 어류 개체군 체장자료의 표집(sampling) 방법 제안

박민규 ( Min Gyou Park ),현상윤 ( Saang-yoon Hyun ) 한국수산과학회(구 한국수산학회) 2021 한국수산과학회지 Vol.54 No.1

In Korea, marine fish landed at ports are randomly sampled on a periodic basis (e.g., daily or weekly), and body sizes (e.g., lengths and weights) of those sampled fish are measured. The motivation for our study is whether or not such measurements reflect the size distribution, especially the length distribution of fish landed (= a population), because such length measurements are key data for a length-based assessment model. The current sampling method is to sample fish landed at ports by body size group (e.g., very small, small, medium, large, very large), using the sampling weights as the number of boxes by body size group. In this study, we showed that length composition data about fish sampled by the current method did not represent the length frequency distribution of the fish landed, and suggested that an alternative sampling method should be applied of using the sampling weights as the number of fish landed by body size group. We also introduced a method for determining an appropriate sample size.

자원복원력 개념을 적용한 사전확률분포 및 상태공간 잉여생산 평가모델: 살오징어(Todarodes pacificus) 개체군 자원평가

김진우 ( Jinwoo Gim ),현상윤 ( Saang-yoon Hyun ),윤상철 ( Sang Chul Yoon ) 한국수산과학회 2022 한국수산과학회지 Vol.55 No.2

It is a difficult task to estimate parameters in even a simple stock assessment model such as a surplus production model, using only data about temporal catch-per-unit-effort (CPUE) (or survey index) and fishery yields. Such difficulty is exacerbated when time-varying parameters are treated as random effects (aka state variables). To overcome the difficulty, previous studies incorporated somewhat subjective assumptions (e.g., B₁=K) or informative priors of parameters. A key is how to build an objective joint prior of parameters, reducing subjectivity. Given the limited data on temporal CPUEs and fishery yields from 1999-2020 for common squid Todarodes pacificus, we built a joint prior of only two parameters, intrinsic growth rate (r) and carrying capacity (K), based on the resilience level of the population (Froese et al., 2017), and used a Bayesian state-space production assessment model. We used template model builder (TMB), a R package for implementing the assessment model, and estimating all parameters in the model. The predicted annual biomass was in the range of 0.76×10⁶ to 4.06×10⁶ MT, the estimated MSY was 0.13×10⁶ MT, the estimated r was 0.24, and the estimated K was 2.10×10⁶ MT.

생활사 기반 모델을 이용한 동해 명태(Gadus chalcogrammus)의 개체군 평가

김규한 ( Kyuhan Kim ),손명호 ( Myoung Ho Sohn ),현상윤 ( Saang-yoon Hyun ) 한국수산과학회(구 한국수산학회) 2017 한국수산과학회지 Vol.50 No.1

Since the late 1990s, walleye pollock Gadus chalcogrammus fisheries in Korean waters have been considered collapsed. Although many fisheries scientists suspect that the collapse might have been triggered by overexploitation of juvenile pollock or environmental changes, such conjectures have been neither tested nor investigated, partially because of limited data on the population. There has been no survey of the population, and the ages of fish in fishery catch have rarely been identified. Instead, fishery catch data from 1975-1997 included information about two life stages, `juveniles and adults,` and data on catch-per-unit-effort (CPUE) during 1963-2007 and those on fish length and weight during 1965-2003 had been sporadically collected from commercial fisheries. To test hypotheses about the collapse of the pollock fisheries, we used a statistical linear model with juvenile CPUE as the response vari-able, and abiotic (e.g., water temperatures) and biotic factors [e.g., adult pollock, flatfishes (Pleuronectidae sp.), and sandfish (Arctoscopus japonicus) CPUEs] as the explanatory variables. The model results indicated that depletion of the pollock population was associated with both biotic (adult pollock and flatfishes abundance) and abiotic factors (mid-water temperatures in February and October). We further interpreted the results from ecological and biological perspectives, suggesting possible mechanisms.

한국 해역의 살오징어(Todarodes pacificus) 개체군 자원평가를 위한 베이지안 상태공간 잉여생산량 모델의 적용

안동영 ( Dongyoung An ),김규한 ( Kyuhan Kim ),강희중 ( Heejung Kang ),현상윤 ( Saang-yoon Hyun ) 한국수산과학회 2021 한국수산과학회지 Vol.54 No.5

Given data about the annual fishery yield of the common squid Todarodes pacificus, and the catch-per-unit-effort (CPUE) data from multiple fisheries from 2000-2018, we applied a Bayesian state - space assessment model for the squid population. One of our objectives was to do a stock assessment, simultaneously incorporating CPUE data from the following three fisheries, (i) large trawl, (ii) jigger, and (iii) large purse seine, which comprised on average a year about 65% of all fisheries, allowing possible correlations to be reflected. Other objectives were to consider both observation and process errors and to apply objective priors of parameters. The estimated annual exploitable biomass was in the range of 3.50×10⁵ to 1.22×10⁶ MT, the estimated intrinsic growth rate was 1.02, and the estimated carry-ing capacity was 1,151,259 MT. Comparison with available results from stock assessment of independently analyzed single fisheries revealed a large difference from the estimated values, suggesting that stock assessment based on multiple fisheries should be performed.