Stock assessment in inland fisheries: a foundation for sustainable use and conservation

Estimation of population abundances in the absence of good observational data are notoriously difficult, yet urgently needed for biodiversity conservation and sustainable use of natural resources. In the field of fisheries research, management regulations have long demanded population abundance estimates even if data available are sparse, leading to the development of a range of fish stock assessment methods designed for data-poor populations. Here, we present methods developed within the context of fisheries research that can be applied to conduct population abundance estimations when facing data-limitations. We begin the review from the less data-demanding approaches and continue with more data-intensive ones. We discuss the advantages and caveats of these approaches, the challenges and management implications associated with data-poor stock assessments, and we propose the implementation of the Bayesian hierarchical framework as the most promising avenue for future development and improvement of the current practices.

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Relative Growth of Three Chionoecetes Crabs (decapoda, Majidae) in the East Sea, Korea

Crustaceana ◽

10.1163/001121611x584316 ◽

2011 ◽

Vol 84 (8) ◽

pp. 897-904

Author(s):

Sung Il Lee ◽

Jung Nyun Kim ◽

Hyun-Woo Kim ◽

Chul-Woong Oh ◽

Jong-Hun Na

Keyword(s):

Stock Assessment ◽

Carapace Width ◽

Sustainable Use ◽

Morphological Characteristics ◽

Hybrid Form ◽

Important Species ◽

Relative Growth ◽

Significant Difference ◽

The Relationship ◽

Snow Crabs

AbstractSnow crabs, Chionoecetes spp., are among the commercially most important species of Decapoda in the world, and proper stock assessment and management are required for their sustainable use. In the present study, morphological characteristics of three snow crabs, Chionoecetes japonicus, Chionoecetes opilio and a hybrid form exhibiting characteristics intermediate between those of the parent species, Chionoecetes japonicus/opilio, have been compared. The ratio of carapace length including rostral horn (CL(RL)) to carapace width (CW) in C. japonicus, C. opilio, and the C. japonicus/opilio hybrid was 0.973 ± 0.020, 0.983 ± 0.019, and 0.956 ± 0.019, respectively. The only significant difference in regression slope among the three crabs, was between CW and chela height (CH), indicating that at a given size, the hybrid form is the fastest in the growth of chela height in relation to carapace width. In C. japonicus and C. opilio, the relationship between CW and total weight (TW) was significantly negatively allometric, while in the hybrids, it was significantly positively allometric. This indicates that at a given size, the hybrid form is heavier than the others.

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Modelling indices of abundance and size-based indicators of cod and flounder stocks in the Baltic Sea using newly standardized trawl survey data

ICES Journal of Marine Science ◽

10.1093/icesjms/fsx005 ◽

2017 ◽

Vol 74 (5) ◽

pp. 1322-1333 ◽

Cited By ~ 14

Author(s):

Alessandro Orio ◽

Ann-Britt Florin ◽

Ulf Bergström ◽

Ivo Šics ◽

Tatjana Baranova ◽

...

Keyword(s):

Time Series ◽

Baltic Sea ◽

Stock Assessment ◽

Generalized Additive Models ◽

Sustainable Use ◽

Demersal Fish ◽

Additive Models ◽

Trawl Survey ◽

The Baltic Sea ◽

The Baltic

Standardized indices of abundance and size-based indicators are of extreme importance for monitoring fish population status. The main objectives of the current study were to (i) combine and standardize recently performed trawl survey with historical ones, (ii) explore and discuss the trends in abundance, and (iii) the trends in maximum length (Lmax) for cod (Gadus morhua) and flounder (Platichthys flesus) stocks in the Baltic Sea. Standardization of catch per unit of effort (CPUE) from trawl surveys from 1978 to 2014 to swept area per unit of time was conducted using information on trawling speed and horizontal opening of the trawls. CPUE data for cod and flounder stocks were modelled using generalized additive models (GAMs) in a delta modelling approach framework, while the Lmax data were modelled using ordinary GAMs. The CPUE time series of the Eastern Baltic cod stock closely resembles the spawning stock biomass trend from analytical stock assessment. The results obtained furnish evidence of the cod spill-over from Subdivisions (SD) 25–28 to SD 24. The decline of Lmax in recent years was evident for both species in all the stocks analysed indicating that the demersal fish community is becoming progressively dominated by small individuals. It is concluded that the standardization of long time series of fisheries-independent data constitutes a powerful tool that could help improve our knowledge on the dynamics of fished populations, thus promoting a long-term sustainable use of these marine resources.

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Comprehensive discard reconstruction and abundance estimation using flexible selectivity functions

ICES Journal of Marine Science ◽

10.1093/icesjms/fsp033 ◽

2009 ◽

Vol 66 (4) ◽

pp. 763-771 ◽

Cited By ~ 36

Author(s):

G. Aarts ◽

J. J. Poos

Keyword(s):

Stock Assessment ◽

Sustainable Use ◽

Abundance Estimation ◽

Commercial Fishing ◽

The North ◽

Minimum Landing Size ◽

The North Sea ◽

Age Model ◽

Age Structured ◽

Precise Time

Abstract Aarts, G., and Poos, J. J. 2009. Comprehensive discard reconstruction and abundance estimation using flexible selectivity functions. – ICES Journal of Marine Science, 66: 763–771. The additional mortality caused by discarding may hamper the sustainable use of marine resources, especially if it is not accounted for in stock assessment and fisheries management. Generally, long and precise time‐series on age-structured landings exist, but historical discard estimates are often lacking or imprecise. The flatfish fishery in the North Sea is a mixed fishery targeting mainly sole and plaice. Owing to the gear characteristics and a minimum landing size for these species, considerable discarding occurs, especially for juvenile plaice. Discard samples collected by on-board observers are available since 1999 from a limited number of commercial fishing trips. Here, we develop a statistical catch-at-age model with flexible selectivity functions to reconstruct historical discards and estimate stock abundance. We do not rely on simple predefined selectivity ogives, but use spline smoothers to capture the unknown non-linear selectivity and discard patterns, and allow these to vary in time. The model is fitted to the age-structured landings, discards, and survey data, the most appropriate model is selected, and estimates of uncertainty are obtained.

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Revisiting the Diversity of Barbonymus (Cypriniformes, Cyprinidae) in Sundaland Using DNA-Based Species Delimitation Methods

Diversity ◽

10.3390/d13070283 ◽

2021 ◽

Vol 13 (7) ◽

pp. 283

Author(s):

Hadi Dahruddin ◽

Arni Sholihah ◽

Tedjo Sukmono ◽

Sopian Sauri ◽

Ujang Nurhaman ◽

...

Keyword(s):

Species Delimitation ◽

Stock Assessment ◽

Dna Barcode ◽

Peninsular Malaysia ◽

Reference Library ◽

Tropical Regions ◽

Operational Taxonomic Units ◽

Inland Fisheries ◽

Large Size ◽

Species Groups

Biodiversity hotspots often suffer from a lack of taxonomic knowledge, particularly those in tropical regions. However, accurate taxonomic knowledge is needed to support sustainable management of biodiversity, especially when it is harvested for human sustenance. Sundaland, the biodiversity hotspot encompassing the islands of Java, Sumatra, Borneo, and Peninsular Malaysia, is one of those. With more than 900 species, its freshwater ichthyofauna includes a large number of medium- to large-size species, which are targeted by inland fisheries. Stock assessment requires accurate taxonomy; however, several species groups targeted by inland fisheries are still poorly known. One of those cases is the cyprinid genus Barbonymus. For this study, we assembled a consolidated DNA barcode reference library for Barbonymus spp. of Sundaland, consisting of mined sequences from BOLD, as well as newly generated sequences for hitherto under-sampled islands such as Borneo. A total of 173 sequences were analyzed using several DNA-based species delimitation methods. We unambiguously detected a total of 6 Molecular Operational Taxonomic Units (MOTUs) and were able to resolve several conflicting assignments to the species level. Furthermore, we clarified the identity of MOTUs occurring in Java.

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