scholarly journals Where is Fisheries Science Heading – How Can Fish Stock Assessments be Improved

1998 ◽  
Vol 23 ◽  
pp. 133-141 ◽  
Author(s):  
Ø Ulltang
Keyword(s):  
Fish Stock ◽  
Fisheries Science ◽  
Stock Assessments

scholarly journals Size-based theory for fisheries advice

2020 ◽  
Author(s):  
K H Andersen
Keyword(s):  
Life History ◽  
Body Size ◽  
Life History Traits ◽  
Fish Stock ◽  
Fisheries Science ◽  
Gear Selectivity ◽  
Stock Assessments

Abstract Fisheries science and management is founded upon the Beverton–Holt theory of fish stock demography. The theory uses age as the structuring variable; however, there are several reasons to use body size as the structuring variable. Most of the processes that affect a fish are determined by its body size rather than its age: consumption, mortality, maturation, fecundity, fish gear selectivity, etc., and measurements of body size are easy, accurate, and abundant. Here, I review size-based theory of a fish stock and compare it to classic age-based theory. I show that size- and age-based demography are equivalent representations of demography. However, size-based theory is axiomatic, which leads to a deeper theory with two advantages: predictions need fewer parameters than age-based theory and the theory connects directly to life-history traits. The connection with traits makes size-based theory particularly useful for data-poor application and facilitates evolutionary calculations. I compare age- and size-based theories for fisheries impact and stock assessments and provide a perspective on the challenges and future of single-stock theory.

scholarly journals Lessons from a career in fisheries science‡

2015 ◽  
Vol 72 (8) ◽  
pp. 2169-2179 ◽  
Author(s):  
Emory D. Anderson
Keyword(s):  
Fishery Management ◽  
Focal Point ◽  
Lessons Learned ◽  
Fish Stock ◽  
Atlantic Mackerel ◽  
Fisheries Science ◽  
High School Math ◽  
Stock Assessments ◽  
Silver Spring ◽  
The Usa

Abstract This article summarizes some of my accomplishments during a 45-year career in fisheries science that ranged from conducting fish stock assessments, working for an international marine science organization, and managing a variety of scientific projects and activities, to finally serving as a scientific editor. In doing so, I have tried to focus on lessons learned. Starting my working life as a high-school math teacher, I soon opted for a different career, returned to the university, and received a PhD in fisheries biology. The first 15 years of my career were at the Woods Hole Laboratory of the National Marine Fisheries Service (NMFS) doing fish stock assessments, where my main interest was Atlantic mackerel (Scomber scombrus). Until the USA declared a 200-mile Exclusive Economic Zone (EEZ) in early 1977, the focal point of my work was the International Commission for the Northwest Atlantic Fisheries (ICNAF). Lasting friendships with scientists from other countries developed during the ICNAF meetings and continued for years thereafter, some to the present day. During 1977–1985, my assessment activities were confined to domestic fisheries and interactions with regional fishery management councils, where I found that a cooperative attitude and the use of non-technical language made a positive impression and helped build trust. Involvement in ICES assessment working groups led, in 1985, to being appointed Statistician in the ICES Secretariat in Copenhagen and the start of an 8-year life in the international community that culminated in becoming General Secretary. Some major changes in ICES in which I was intimately involved are discussed. After my return to the USA in 1994, my career included managing a variety of activities and projects in Woods Hole and at NOAA/NMFS headquarters in Silver Spring, MD (where I was NMFS liaison to the National Sea Grant Office), finally concluding, after my retirement from NMFS in 2004, with continued engagement in fisheries science as an editor for ICES. Having benefited from experiences in science and administration and the lessons learned therein, it is a pleasure, via this article, to offer advice to young scientists contemplating potential paths to pursue in their careers.

scholarly journals Effective fisheries management instrumental in improving fish stock status

2020 ◽  
Vol 117 (4) ◽  
pp. 2218-2224 ◽  
Author(s):  
Ray Hilborn ◽  
Ricardo Oscar Amoroso ◽  
Christopher M. Anderson ◽  
Julia K. Baum ◽  
Trevor A. Branch ◽  
...  
Keyword(s):  
Fisheries Management ◽  
Marine Fish ◽  
Food System ◽  
Fish Stock ◽  
Management Tools ◽  
Fish Stocks ◽  
Fisheries Science ◽  
The World ◽  
Fish Catch ◽  
Intensively Managed

Marine fish stocks are an important part of the world food system and are particularly important for many of the poorest people of the world. Most existing analyses suggest overfishing is increasing, and there is widespread concern that fish stocks are decreasing throughout most of the world. We assembled trends in abundance and harvest rate of stocks that are scientifically assessed, constituting half of the reported global marine fish catch. For these stocks, on average, abundance is increasing and is at proposed target levels. Compared with regions that are intensively managed, regions with less-developed fisheries management have, on average, 3-fold greater harvest rates and half the abundance as assessed stocks. Available evidence suggests that the regions without assessments of abundance have little fisheries management, and stocks are in poor shape. Increased application of area-appropriate fisheries science recommendations and management tools are still needed for sustaining fisheries in places where they are lacking.

How much evidence is required for acceptance of productivity regime shifts in fish stock assessments: Are we letting managers off the hook?

2015 ◽  
Vol 168 ◽  
pp. 49-55 ◽  
Author(s):  
Neil L. Klaer ◽  
Robert N. O’Boyle ◽  
Jonathan J. Deroba ◽  
Sally E. Wayte ◽  
L. Richard Little ◽  
...  
Keyword(s):  
Regime Shifts ◽  
Fish Stock ◽  
Stock Assessments

Marine parasites as biological tags in South American Atlantic waters, current status and perspectives

Parasitology ◽  
2014 ◽  
Vol 142 (1) ◽  
pp. 5-24 ◽  
Author(s):  
D. M. P. CANTATORE ◽  
J. T. TIMI
Keyword(s):  
Current Status ◽  
Future Research ◽  
Fish Stock ◽  
South American ◽  
Fish Parasite ◽  
New Paradigm ◽  
Essential Information ◽  
Fisheries Science ◽  
Ecosystem Boundaries ◽  
Biological Tags

SUMMARYMany marine fisheries in South American Atlantic coasts (SAAC) are threatened by overfishing and under serious risk of collapsing. The SAAC comprises a diversity of environments, possesses a complex oceanography and harbours a vast biodiversity that provide an enormous potential for using parasites as biological tags for fish stock delineation, a prerequisite for the implementation of control and management plans. Here, their use in the SAAC is reviewed. Main evidence is derived from northern Argentine waters, where fish parasite assemblages are dominated by larval helminth species that share a low specificity, long persistence and trophic transmission, parasitizing almost indiscriminately all available fish species. The advantages and constraints of such a combination of characteristics are analysed and recommendations are given for future research. Shifting the focus from fish/parasite populations to communities allows expanding the concept of biological tags from local to regional scales, providing essential information to delineate ecosystem boundaries for host communities. This new concept arose as a powerful tool to help the implementation of ecosystem-based approaches to fisheries management, the new paradigm for fisheries science. Holistic approaches, including parasites as biological tags for stock delineation will render valuable information to help insure fisheries and marine ecosystems against further depletion and collapse.

scholarly journals Age-specific differences in the seasonal spatial distribution of butterfish (Peprilus triacanthus)

2016 ◽  
Vol 74 (1) ◽  
pp. 170-179 ◽  
Author(s):  
Charles F. Adams
Keyword(s):  
Time Series ◽  
Spatial Distribution ◽  
Reference Points ◽  
Trawl Survey ◽  
Spatial Equilibrium ◽  
Science Center ◽  
Fisheries Science ◽  
Specific Analysis ◽  
Stock Assessments ◽  
Seasonal Analysis

The spatial distribution of butterfish (Peprilus triacanthus) in the Northwest Atlantic Ocean was investigated using a suite of spatial indicators based on Northeast Fisheries Science Center spring and fall bottom trawl survey data, 1982–2013. In the spring, ages 2 and 3 were found farther northeast and deeper than age 1 butterfish, while in the fall, age 3 butterfish were found farther northeast and deeper than ages 0 and 1. There was no significant northward movement of butterfish in spring or fall over the course of either time-series. However, there was a significant increase in the area occupied by ages 1–3 in the spring that was correlated with surface temperature. This illustrates that responses to climate change may be manifested as range expansions, rather than poleward movement of the centre of gravity (i.e. bivariate weighted mean location of the population). Two changes were observed over the course of the fall time series, both for ages 1 and 2: increased spatial dispersion; and a decrease in depth. The former result would have been masked, while the latter would have been erroneously generalized to all age classes, if an age-specific analysis had not been done. This study demonstrates the importance of an age-based and seasonal analysis. It is also shown how a spatial distribution analyses can inform stock assessments by providing insights into diverging survey indices and availability to surveys in general. Similarly, spatial distribution analyses can be used to verify the spatial equilibrium assumption for the calculation of biological reference points.

Accounting for marine reserves using spatial stock assessments

2015 ◽  
Vol 72 (2) ◽  
pp. 262-280 ◽  
Author(s):  
Carey R. McGilliard ◽  
André E. Punt ◽  
Richard D. Methot ◽  
Ray Hilborn
Keyword(s):  
Spatial Heterogeneity ◽  
Stock Assessment ◽  
Marine Reserves ◽  
Movement Patterns ◽  
Catch Rate ◽  
Fish Stock ◽  
Rate Data ◽  
Stock Assessments ◽  
Age Structured ◽  
Movement Parameters

Some fish stock assessments are conducted in regions that contain no-take marine reserves (NTMRs). NTMRs are expected to lead to spatial heterogeneity in fish biomass by allowing a buildup of biomass inside their borders while fishing pressure occurs outside. Stock assessments do not typically account for spatial heterogeneity caused by NTMRs, which may lead to biased estimates of biomass. Simulation modeling is used to analyze the ability of several stock assessment configurations to estimate current biomass after the implementation of a single, large NTMR. Age-structured spatial operating models with three patterns of ontogenetic movement are used to represent the “true” population dynamics. Results show that assessing populations as a single stock with use of fishery catch-rate data and without accounting for the NTMR results in severe underestimation of biomass for two of the movement patterns. Omitting fishery catch-rate data or allowing time-varying dome-shaped selectivity after NTMR implementation leads to improved estimates of current biomass, but severe bias in estimated trends in biomass over time. Performing separate assessments for fished areas and NTMRs leads to improved estimation performance in the absence of movement among assessment areas, but can severely overestimate biomass otherwise. Performing a spatial assessment with estimation of movement parameters among areas was found to be the best way to assess a species, even when movement patterns were unknown. However, future work should explore the performance of spatial assessments when catchability varies among areas.

Fish stock assessments in Lake Konnevesi

Hydrobiologia ◽  
1982 ◽  
Vol 86 (1-2) ◽  
pp. 219-222 ◽  
Author(s):  
J. Toivonen ◽  
H. Auvinen ◽  
P. Valkeaj�rvi
Keyword(s):  
Fish Stock ◽  
Stock Assessments

scholarly journals Importance of modelling heteroscedasticity of survey index data in fishery stock assessments

2014 ◽  
Vol 72 (1) ◽  
pp. 130-136 ◽  
Author(s):  
Saang-Yoon Hyun ◽  
Mark N. Maunder ◽  
Brian J. Rothschild
Keyword(s):  
Coefficient Of Variation ◽  
Likelihood Function ◽  
Error Model ◽  
Fish Stock ◽  
Additional Parameter ◽  
Traditional Practice ◽  
Multiplicative Error ◽  
Additive Error ◽  
Stochastic Error ◽  
Stock Assessments

Abstract Many fish stock assessments use a survey index and assume a stochastic error in the index on which a likelihood function of associated parameters is built and optimized for the parameter estimation. The purpose of this paper is to evaluate the assumption that the standard deviation for the difference in the log-transformed index is approximately equal to the coefficient of variation of the index, and also to examine the homo- and heteroscedasticity of the errors. The traditional practice is to assume a common variance of the index errors over time for estimation convenience. However, if additional information is available about year-to-year variability in the errors, such as year-to-year coefficient of variation, then we suggest that the heteroscedasticity assumption should be considered. We examined five methods with the assumption of a multiplicative error in the survey index and two methods with that of an additive error in the index: M1, homoscedasticity in the multiplicative error model; M2, heteroscedasticity in the multiplicative error model; M3, M2 with approximate weighting and an additional parameter for scaling variance; M4–M5, pragmatic practices; M6, homoscedasticity in the additive error model; M7, heteroscedasticity in the additive error model. M1–M2 and M6–M7 are strictly based on statistical theories, whereas M3–M5 are not. Heteroscedasticity methods M2, M3, and M7 consistently outperformed the other methods. However, we select M2 as the best method. M3 requires one more parameter than M2. M7 has problems arising from the use of the raw scale as opposed to the logarithm transformation. Furthermore, the fitted survey index in M7 can be negative although its domain is positive.

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