Does size matter? A cautionary experiment on overoptimism in length-based bioresource assessment

2007 ◽  
Vol 64 (7) ◽  
pp. 996-1008 ◽  
Author(s):  
Duane B Fonseca ◽  
Matt RJ Sheehy
Keyword(s):  
Growth Parameters ◽  
Stock Assessment ◽  
Age Determination ◽  
Relative Yield ◽  
Parameter Estimates ◽  
Freshwater Crayfish ◽  
Biological Reality ◽  
Length Increment ◽  
Size Matter ◽  
First Time

Recently, there has been considerable progress in the development of neurolipofuscin-based age determination methods for crustacean stock assessment. Initial applications to lobster and crab fisheries suggest some important method-related differences between conventional length-based assessment parameter estimates and those derived with the new aging technique. Here, for the first time, we aim to clarify the basis for and implications of some of these discrepancies using an experimental fishery context. We estimate von Bertalanffy growth parameters (k and l∞), longevity (tmax), total and natural mortality (Z and M, respectively), maximum sustainable relative yield-per-recruit (MSY'/R), and the exploitation rate that produces MSY'/R (EMSY'/R) for a freshwater crayfish (Pacifastacus leniusculus) population by length–frequency analysis and tag–recapture (length-increment-at-length) and compare these results with simultaneous neurolipofuscin demographic estimates. Our central finding is that the length-based approaches are largely blind to the biological reality of asymptotic postmaturational growth, with the consequence that longevity is prone to underestimation, late growth trajectories and mortality rates to inflation, and sex differences to misjudgment. This inherent bias is likely to lead to pervasive undervaluing of potential yields and overly optimistic target exploitation rates that will heighten the risk of growth and recruitment overfishing. Neurolipofuscin offers a means of identifying and overcoming this important problem.

scholarly journals Length-Based Stock Assessment of Smith's Barb, Puntioplites proctozystron (Bleeker, 1865) (Cyprinidae) and Asian Redtail Catfish, Hemibagrus nemurus, (Valenciennes, 1840), (Bagridae) in a Multipurpose Reservoir in Thailand

2021 ◽  
Vol 34 (2) ◽  
Author(s):  
KAJITPAN CHARERNNATE ◽  
PAVAROT NORANARTTRAGOON ◽  
TUANTONG JUTAGATE ◽  
Keyword(s):  
Growth Parameters ◽  
Stock Assessment ◽  
Relative Yield ◽  
Mesh Size ◽  
Fish Stock ◽  
Fish Stocks ◽  
The Status ◽  
Curvature Parameter ◽  
Spawning Potential Ratio ◽  
Fish Stock Assessment

Catches from inland fisheries in Thailand are about 200,000 tonnes annually and plays an important role in food security and subsidiary income. However, fish stocks are seldom assessed because of the lack of catch and effort data. In this study, two fish stock assessment models, viz., relative yield per recruit and length-based spawning potential ratio, were used to evaluate the status of two species as well as to highlight their applications to datalimited situation in Thailand. The study was conducted at Kangkrajan Reservoir, Thailand, for two targeted species, viz., Smith's barb, Puntioplites proctozystron (Bleeker, 1865) and Asian redtail catfish, Hemibagrus nemurus (Valenciennes, 1840) using length frequency data. The data were collected throughout 2019. Both species showed isometric growth. Von Bertalanffy growth parameters were estimated. Asymptotic length, curvature parameter and theoretical age at length zero were 36.2 cm TL, 0.39 yr-1 and -0.28 yr for P. proctozystron, respectively, and 63.2 cm TL, 0.37 yr-1 and -0.32 yr for H. nemurus. The exploitation rates reveal that both species are slightly overfished. Sizes at 50 % maturity and 50 % selectivities were 17.8 and 23.5 cm TL for P. proctozystron, respectively, and 15.6 and 20.8 cm TL for H. nemurus. Considering both parameters, the size at first capture to sustain the fisheries of P. proctozystron and H. nemurus should be >18 cm and >30 cm, respectively, which can be achieved by mesh-size regulations.

Growth of cod (Gadus morhua) in the western Baltic Sea: estimating improved growth parameters from tag–recapture data

2019 ◽  
Vol 76 (8) ◽  
pp. 1326-1337 ◽  
Author(s):  
Kate McQueen ◽  
J. Paige Eveson ◽  
Bodo Dolk ◽  
Thomas Lorenz ◽  
Thomas Mohr ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Gadus Morhua ◽  
Growth Parameters ◽  
Age Determination ◽  
Artificial Reef ◽  
Growth Parameter ◽  
Growth Function ◽  
Fish Growth ◽  
Parameter Estimates ◽  
Data Set

Tag–recapture data contain valuable information about individual fish growth, which can enhance the estimation of growth parameters. Tag–recapture data are especially useful when age-determination uncertainties throw age-based growth estimates and stock assessments into question, as is the present situation with several important gadoid stocks. Length-based (GROTAG method) and age-based (LEP method) growth functions were fit to a large data set of tagged and recaptured cod (Gadus morhua) from an artificial reef in the western Baltic Sea to calculate improved growth parameter estimates. The LEP method allowed integration of different data formats, including tag–recapture, length frequency, and length-at-age, to estimate a more robust and comprehensive growth function (von Bertalanffy growth parameters: L∞ = 154.56 cm, k = 0.11, t0 = –0.13). Two heavily exploited cod stocks inhabit the Baltic Sea, subsisting at the upper thermal and lower salinity limits of the species. Otolith shape analyses indicated that, unexpectedly, individuals from both populations were resident at the reef. Compared with cod populations elsewhere, cod in the western Baltic Sea grow relatively slowly and with weak seasonal fluctuations in growth rates, potentially due to adverse conditions for growth.

scholarly journals Population dynamics of an invasive species Carassius auratus in the Shatt Al-Arab River, Iraq

2020 ◽  
Vol 5 (3) ◽  
pp. 384-389
Author(s):  
Abdullah N. Abood ◽  
Abdul-Razak M. Mohamed
Keyword(s):  
Population Dynamics ◽  
Carassius Auratus ◽  
Assessment Tool ◽  
Growth Parameters ◽  
Stock Assessment ◽  
Relative Yield ◽  
Reference Points ◽  
Fish Length ◽  
Exploitation Rate ◽  
Precautionary Measures

The population dynamics of the crucian carp, Carassius auratus in the Shatt Al-Arab River, Iraq was studied from November 2015 to October 2016 with monthly samples collected by different fishing gears. The FAO-ICLARM Stock Assessment Tool (FiSAT II) software was used for the mathematical analysis. Length-weight relationship was calculated as W= 0.0149L3.065 for fish length 4.6 to 26.8 cm. Growth parameters L∞, K and Ø were computed as 29.1 cm, 0.51 and 2.635. The total (Z), natural (M) and fishing (F) mortalities were 2.69, 1.09 and 1.60, respectively. Exploitation rate (E) was 0.59. Length at first capture (Lc) was found to be 10.04 cm. C. auratus displayed one main pulse of annual recruitment. The relative yield per recruit analysis revealed that the exploitation rate (E) of C. auratus was higher than the biological target reference points E0.1 and equivalent to Emax. It could be concluded that the C. auratus stock in the Shatt Al-Arab River is operating nearby the exploited situation and needs some precautionary measures to avoid the overexploitation by activating the national law of fishing, exploiting and protecting aquatic resources, in particular preventing illegal fishing methods and follow up the execution of the closed season to prevent the decline of our fish resources.

scholarly journals Electrochromic Performance and Capacitor Performance of α-MoO3 Nanorods Fabricated by a One-Step Procedure

Coatings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 783
Author(s):  
Ying Duan ◽  
Chen Wang ◽  
Jian Hao ◽  
Yang Jiao ◽  
Yanchao Xu ◽  
...  
Keyword(s):  
Growth Parameters ◽  
Average Diameter ◽  
Fast Response ◽  
Cycle Stability ◽  
Electrochromic Devices ◽  
Step Procedure ◽  
One Step ◽  
Supercapacitor Performance ◽  
First Time ◽  
Prepared Nanorods

In this paper, we propose for the first time the synthesis of α-MoO3 nanorods in a one-step procedure at mild temperatures. By changing the growth parameters, the microstructure and controllable morphology of the resulting products can be customized. The average diameter of the as-prepared nanorods is about 200 nm. The electrochromic and capacitance properties of the synthesized products were studied. The results show that the electrochromic properties of α-MoO3 nanorods at 550 nm have 67% high transmission contrast, good cycle stability and fast response time. The MoO3 nanorods also exhibit a stable supercapacitor performance with 98.5% capacitance retention after 10,000 cycles. Although current density varies sequentially, the nanostructure always exhibits a stable capacitor to maintain 100%. These results indicate the as-prepared MoO3 nanorods may be good candidates for applications in electrochromic devices and supercapacitors.

scholarly journals Directly ageing the Caribbean spiny lobster, Panulirus argus with validated band counts from gastric mill ossicles

2018 ◽  
Vol 76 (2) ◽  
pp. 442-451 ◽  
Author(s):  
Gaya Gnanalingam ◽  
Mark J Butler ◽  
Thomas R Matthews ◽  
Emily Hutchinson ◽  
Raouf Kilada
Keyword(s):  
Spiny Lobster ◽  
Age Determination ◽  
Florida Keys ◽  
Panulirus Argus ◽  
Gastric Mill ◽  
Coefficients Of Variation ◽  
The Caribbean ◽  
First Time ◽  
Reader Experience

Abstract In crustaceans, ecdysis was long believed to result in the loss and replacement of all calcified structures, precluding the use of conventional ageing methods. However, the discovery of bands in the gastric ossicles of several crustaceans with some correlation with age suggests that direct age estimation may be possible. We applied this method to a tropical spiny lobster, Panulirus argus, one of the most iconic and economically valuable species in the Caribbean. The presence of growth bands was investigated using wild lobsters of unknown age and was validated with captive reared lobsters of known age (1.5–10 years) from the Florida Keys, Florida (USA). Bands were consistently identified in ptero- and zygo-cardiac ossicles of the gastric mill and did not appear to be associated with moulting. Validation with known age animals confirms that bands form annually. Counts between independent readers were reproducible with coefficients of variation ranging from 11% to 26% depending on reader experience and the structure used. This study demonstrates, for the first time, that direct age determination of P. argus is possible.

Growth Models with Corrections for the Retardative Effects of Tagging

1994 ◽  
Vol 51 (2) ◽  
pp. 263-267 ◽  
Author(s):  
Yongshun Xiao
Keyword(s):  
Growth Parameters ◽  
Growth Models ◽  
Simulated Data ◽  
Fish Growth ◽  
Lates Calcarifer ◽  
General Utility ◽  
Potential Applications ◽  
Length Increment ◽  
Animal Growth ◽  
Special Case

Length increment data from mark–recapture experiments are commonly used to obtain information on animal growth, assuming that tagging does not affect the growth of marked animals. The assumption is violated in many studies, but the effects of tagging on growth and estimates of growth parameters have not been and cannot be examined without appropriate models. This paper describes a model allowing quantification and estimation of the retarding effects of tagging on animal growth simultaneously with growth parameters in all existing growth models, reduction or elimination of biases in growth parameters induced by tagging, and relaxation of a key assumption in growth analysis using length increment data. A special case of this model was applied to simulated data and to tagging data from a centropomid perch (Lates calcarifer) to demonstrate its general utility. Tagging was inferred to have stopped the fish growth for 36.44 d (ASE = 12.70 d) if von Bertalanffy growth is assumed, but the period of recovery from tagging seemed size or age independent within the size range studied. If tagging retards animal growth, L∞ is slightly overestimated and K underestimated for unbiased data. Potential applications and limitations of the model are also discussed.

scholarly journals Age, Growth and Ovarian Histology of Sardinella aurita (Valenciennes, 1847) in the South of Atlantic Moroccan Coast

2021 ◽  
Vol 21 (04) ◽  
pp. 191-204
Author(s):  
Ayoub Baali ◽  
Oum Keltoum Belhsen ◽  
Khalil Chahdi Ouazzani ◽  
Khadija Amenzoui ◽  
Ahmed Yahyaoui
Keyword(s):  
Frequency Distribution ◽  
Stock Assessment ◽  
Atlantic Coast ◽  
Age Groups ◽  
Age Determination ◽  
Length Frequency Distribution ◽  
Length Frequency ◽  
The South ◽  
Moroccan Coast ◽  
Sardinella Aurita

Otoliths reading and length frequency distribution were used for age determination and growth estimation of Sardinella aurita (round sardinella) stock of Southern Atlantic coast of Morocco. Both otoliths' method for age determination and Bhattacharya’s method for length frequency analysis showed five age groups. The growth performance index revealed that there is significant accordance among method of length frequency distribution and otoliths reading for stock assessment studies of Sardinella aurita stock in the south of Morocco. The microscopic observation of female gonads using histology method was investigated for the first time in our study area and confirms the presence of five principal stages of ovary of sardinella aurita: immature, maturing virgin and recovering spent, mature (or pre-spawning phase), spawning, post-spawning or spent. In addition, our results of the fecundity showed that the mean relative fecundity obtained is estimated at 193 ± 98 oocytes/g which is lower compared to those obtained in other areas in the Atlantic coast.

Population dynamics and stock assessment of Hilsa shad, Tenualosa ilisha (Hamilton, 1822) along the coast of Bangladesh

2021 ◽  
Vol 48 (2) ◽  
pp. 231-241
Author(s):  
Md Khairul Islam ◽  
Md Humayun ◽  
Manmatha Nath Sarker ◽  
Md Sharifuddin ◽  
M Niamul Naser
Keyword(s):  
Growth Parameters ◽  
Stock Assessment ◽  
Population Analysis ◽  
Total Mortality ◽  
Maximum Sustainable Yield ◽  
Fishing Mortality ◽  
Recruitment Pattern ◽  
Weight Relationship ◽  
Tenualosa Ilisha ◽  
Highly Correlated

Stock Assessment of Tenualosa ilisha (Hamilton, 1822) were estimated using FiSAT-II software with length-frequency data collected from different landing centers. The Southeast Coast of Bay Of Bengal, Cox's Bazar. The Von Bertalanffy growth parameters Land K for the species were asymptotic length (L∞) was 51.41 cm, growth rate (K) was 0.75 year-1 and t0 = -0.2 year respectively. The estimated value of total mortality (Z) based on length converted catch curve using these growth parameters was 2.35 year-1.Natural mortality (M) based on growth parameters and mean environmental temperature (T = 27° C) was 1.00 year-1 and fishing mortality (F) was 1.35 year-1. Optimum length of hilsa at first capture (Lc=L50) was 28.36 cm TL. Growth performance indices (ϕ') was 3.30. The estimated value of the exploitation rate (E) using the length-converted catch curve was 0.57. The recruitment pattern of this species was continuous and two peaks per year. The present investigation clearly showed the over fishing (E > 0.50) condition for T. ilisha in Bangladesh. The estimated length-weight relationship for the combined sex was found to be W = 0.0109 L3. Virtual population analysis (VPA) showed that the maximum fishing mortality occurring in the length between 30 to 35 cm with a maximum value in the length of 32 cm that repeatedly indicate high fishing mortality in the T. ilisha. The generalized length-weight relationship was fitted with the pooled data of all monthly samples were BW = 0.029 TL2.718 (R2= 0.833) respectively. The results revealed that all length-weight relationships were highly correlated (r > 0.993). Maximum sustainable yield (MSY) was estimated as 435,554 t. Bangladesh J. Zool. 48(2): 231-241, 2020

Year-class detection reveals climatic modulation of settlement strength in the European lobster, Homarus gammarus

2002 ◽  
Vol 59 (7) ◽  
pp. 1132-1143 ◽  
Author(s):  
M R.J Sheehy ◽  
R C.A Bannister
Keyword(s):  
Stock Assessment ◽  
Global Climate ◽  
Larval Settlement ◽  
European Lobster ◽  
Homarus Gammarus ◽  
Cross Correlation Analysis ◽  
Age Dependent ◽  
Intractable Problem ◽  
First Time

Understanding the nature of recruitment relationships in the European lobster, Homarus gammarus, has been an intractable problem because of difficulties associated with quantification of its scarce planktonic larvae and early benthic phase. We attempt to address this problem by analyzing the age composition of a population off the northeast coast of England. Age-dependent in situ deposits of neurolipofuscin in the eyestalk are used as an age index. An approach is presented that accounts and (or) corrects for the two most important potential sources of error in age determinations by this technique, namely environmental temperature variation and unexplained individual variation. This yields, for the first time in very long-lived clawed lobsters, reproducible catch age structures with year-class resolution. The method should be generally applicable to crustaceans. Cross-correlation analysis shows that larval settlement strength in the European lobster is associated with local sea temperatures and onshore winds in a manner similar to that reported for other lobsters. These findings have important implications for stock assessment, particularly the use of traditional models dependent on size and steady state, yield forecasting, the effects of global climate change, arguments about spawner protection or restocking, and the spawner–recruit relationship.

scholarly journals Two-step Procedure Based on the Least Squares and Instrumental Variable Methods for Simultaneous Estimation of von Bertalanffy Growth Parameters

2019 ◽  
Vol 10 (2) ◽  
pp. 49-81 ◽  
Author(s):  
Ivelina Yordanova Zlateva ◽  
Nikola Nikolov
Keyword(s):  
Least Squares ◽  
Instrumental Variable ◽  
Initial Conditions ◽  
Growth Parameters ◽  
Individual Growth ◽  
Simultaneous Estimation ◽  
Parameter Estimates ◽  
Growth Equation ◽  
Von Bertalanffy ◽  
Step Procedure

Advanced in the present article is a Two-step procedure designed on the methods of the least squares (LS) and instrumental variable (IV) techniques for simultaneous estimation of the three unknown parameters L∞, K and t0, which represent the individual growth of fish in the von Bertalanffy growth equation. For the purposes of the present analysis, specific MATLAB-based software has been developed through simulated data sets to test the operational workability of the proposed procedure and pinpoint areas of improvement. The resulting parameter estimates have been analyzed on the basis of consecutive comparison (the initial conditions being the same) between the results delivered by the two-step procedure for simultaneous estimation of L∞, K and t0 and the results obtained via the most commonly employed methods for estimating growth parameters; first, use has been made of the Gulland-and-Holt method for estimating the asymptotic length L∞and the curvature parameter K, followed by the von Bertalanffy method for estimation of t0.

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