Integrating seabird dietary and groundfish stock assessment data: Can puffins predict pollock spawning stock biomass in the North Pacific?

Abstract van Damme, C. J. G., Bolle, L. J., Fox, C. J., Fossum, P., Kraus, G., Munk, P., Rohlf, N., Witthames, P. R., and Dickey-Collas, M. 2009. A reanalysis of North Sea plaice spawning-stock biomass using the annual egg production method. – ICES Journal of Marine Science, 66: 1999–2011. Uncertainty about the quality of current virtual population analysis-based stock assessment for North Sea plaice (Pleuronectes platessa) has led to various abundance indices. We compared biomass estimates from the annual egg production (AEP) method with current stock assessments based on catch-at-age to validate the current and historical perception of exploitation. The AEP method was also used to investigate the dynamics of the spatial components of plaice in the North Sea. We corrected for fecundity down-regulation and changes in sex ratio. Estimates from both methods were similar in trend and absolute biomass. On the Dogger Bank, there was a dramatic decline in biomass from 1948 and 1950 to 2004, and in the Southern Bight, the stock appeared to increase from 1987 and 1988 to 2004, although not reaching the historically high levels of 1948 or 1950. The timing of spawning of North Sea plaice does not appear to have changed throughout the period of high exploitation. We conclude that the AEP method is a useful way to hindcast the spatial dynamics of heavily exploited flatfish stocks.

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Stock assessment of the autumn cohort of neon flying squid (Ommastrephes bartramii) in the North Pacific based on past large-scale high seas driftnet fishery data

Fisheries Research ◽

10.1016/j.fishres.2006.01.003 ◽

2006 ◽

Vol 78 (2-3) ◽

pp. 286-297 ◽

Cited By ~ 32

Author(s):

Taro Ichii ◽

Kedarnath Mahapatra ◽

Hiroshi Okamura ◽

Yoshihiro Okada

Keyword(s):

North Pacific ◽

Large Scale ◽

Stock Assessment ◽

Ommastrephes Bartramii ◽

The North ◽

Fishery Data ◽

Neon Flying Squid ◽

The North Pacific ◽

High Seas

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Population dynamics and stock assessment of grey sharpnose shark Rhizoprionodon oligolinx Springer, 1964 (Chondrichthyes: Carcharhinidae) from the north-west coast of India

Indian Journal of Fisheries ◽

10.21077/ijf.2017.64.3.67657-02 ◽

2017 ◽

Vol 64 (3) ◽

Author(s):

G. B. Purushottama ◽

Gyanaranjan Dash ◽

Thakur Das ◽

K. V. Akhilesh ◽

Shoba Joe Kizhakudan ◽

...

Keyword(s):

Population Dynamics ◽

Stock Assessment ◽

Total Mortality ◽

North West ◽

The North ◽

Stock Biomass ◽

Spawning Stock ◽

Yield Per Recruit ◽

Peak Phase

The life history and exploitation parameters of Rhizoprionodon oligolinx Springer, 1964 were assessed using commercial landing data of 2012-2015 from Mumbai waters of India to understand the population dynamics and stock status of the species. The average annual landing of the species was estimated to be 383 t, which formed about 9.1% of the total shark landings of Maharashtra. L∞, K and t0 estimated were 97.1 cm, 0.47 yr-1 and -0.79 yr respectively. Total mortality (Z), fishing mortality (F) and natural mortality (M) rates were estimated as 2.16 yr-1, 1.48 yr-1 and 0.69 yr-1 respectively. The length at capture (L50), length at female maturity (Lm50) and male maturity (Lm50) were estimated as 49.7, 62.3 and 59.5 cm respectively, which indicated that most of the sharks entered peak phase of exploitation before attaining sexual maturity. Length-weight relationship indicated allometric growth (b>3) for the species. The species was found to be a continuous breeder and showed peak recruitment during April. The current exploitation rate (Ecur) was found to be 0.68, which is lower than Emax estimated for the species using Beverton and Holt yield per recruit analysis. Thompson and Bell prediction model showed that at current exploitation level, the biomass (B) has reduced to 32% of virgin biomass (B0) where as, the spawning stock biomass (SSB) has reduced to 16% of the virgin spawning stock biomass (SSB0). Hence the exploitation level for the species should be reduced by 40% that will ensure the availability of SSB at a relatively safer 30% level to rebuild the stock for long term sustainability of the resource.

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Maturity and growth population dynamics of Norway pout (Trisopterus esmarkii) in the North Sea, Skagerrak, and Kattegat

ICES Journal of Marine Science ◽

10.1093/icesjms/fsp153 ◽

2009 ◽

Vol 66 (9) ◽

pp. 1899-1914 ◽

Cited By ~ 12

Author(s):

Gwladys Lambert ◽

J. Rasmus Nielsen ◽

Lena I. Larsen ◽

Henrik Sparholt

Keyword(s):

Population Dynamics ◽

North Sea ◽

Stock Assessment ◽

Age Group ◽

Commercial Catch ◽

The North ◽

Stock Biomass ◽

Spawning Stock ◽

The North Sea ◽

Immature Fish

Abstract Lambert, G., Nielsen, J. R., Larsen, L. I., and Sparholt, H. 2009. Maturity and growth population dynamics of Norway pout (Trisopterus esmarkii) in the North Sea, Skagerrak, and Kattegat. – ICES Journal of Marine Science, 66: 1899–1914. The population dynamics of the Norway pout stock in the North Sea are investigated by statistical analyses, and GIS of ICES International Bottom Trawl Surveys (IBTS) and Danish commercial catch data from 1983 to 2006. The stock spawns mainly around mid-February along the northeastern English and Scottish coasts and between Shetland and Norway. Sex ratios indicate that males, which mature younger than females (age-at-50%-maturity, respectively, 1.2 and 1.5 years), migrate out of the Skagerrak–Kattegat to the spawning grounds before females. There is a decrease in the 2+-group maturity ratios as well as in weight and female length from before to after spawning. The results indicate spawning mortality. Only some 20% of the 1-group reaches maturity in the first quarter, which is higher than assumed in the stock assessment. Although the maturity ogives are variable over time, this difference should be taken into account when estimating spawning-stock biomass in routine assessments. Growth is also variable, with a tendency for male maximum length to be smaller than that of females, and immature fish to be smaller than mature ones in each age group. The juvenile growth rate is higher when the stock density is low and results in a reduced age-at-50%-maturity. Besides these intraspecific patterns, the growth rates show interspecific links to stock sizes of the important predators: cod, haddock, and whiting.

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Estimating uncertainty of data limited stock assessments

ICES Journal of Marine Science ◽

10.1093/icesjms/fsw145 ◽

2016 ◽

Vol 74 (1) ◽

pp. 69-77 ◽

Cited By ~ 15

Author(s):

Alexandros Kokkalis ◽

Anne Maria Eikeset ◽

Uffe H. Thygesen ◽

Petur Steingrund ◽

Ken H. Andersen

Keyword(s):

Stock Assessment ◽

Assessment Method ◽

Fish Stocks ◽

Stock Status ◽

North East ◽

The North ◽

Stock Biomass ◽

Uncertainty Estimates ◽

Stock Assessments ◽

Spawning Stock

Many methods exist to assess the fishing status of data-limited stocks; however, little is known about the accuracy or the uncertainty of such assessments. Here we evaluate a new size-based data-limited stock assessment method by applying it to well-assessed, data-rich fish stocks treated as data-limited. Particular emphasis is put on providing uncertainty estimates of the data-limited assessment. We assess four cod stocks in the North-East Atlantic and compare our estimates of stock status (F/Fmsy) with the official assessments. The estimated stock status of all four cod stocks followed the established stock assessments remarkably well and the official assessments fell well within the uncertainty bounds. The estimation of spawning stock biomass followed the same trends as the official assessment, but not the same levels. We conclude that the data-limited assessment method can be used for stock assessment and that the uncertainty estimates are reliable. Further work is needed to quantify the spawning biomass of the stock.

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