A Bumpy Old Road: Size-Based Methods in Fisheries Assessment

Pitcher, Tony J.

doi:10.1002/9780470693919.ch9

Cited by 9 publications

(14 citation statements)

References 26 publications

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Section: Discussionmentioning

confidence: 99%

“…Where multiple L ∞ and k values exist for a species in the literature, auximetric plots can be used to indicate the accuracy of the L ∞ and k values obtained by a new study as any values of that fall outside the boundaries of region characteristic for a given species can be considered as incorrect (Pitcher, ). Figure shows the auximetric plot for the genus Pomadasys with the expected general negative relationship between L ∞ and k (Pitcher, ) observed. Although the data for small spotted grunt are very limited (3 published studies, Table ), the L ∞ and k values obtained in the present study fall within the auximetric plot for the species and within the spread of data observed for the genus (Figure ) providing confidence in the VBG data.…”

Section: Discussionmentioning

confidence: 99%

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Age and growth validation of the small spotted grunt Pomadasys commersonnii (Lacepède, 1801) from the northwestern coast of the Arabian Sea of Oman

2018

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Summary Age structure and growth parameters were determined for a population of small spotted grunt, Pomadasys commersonnii in the Arabian Sea. Small spotted grunt samples were collected monthly between September 2007 and August 2008 by beam trawl [40 mm cod‐end mesh size] surveys conducted along the Arabian Sea coast of Oman from Ras Al‐Had in the north to the Oman‐Yemen border in the south west of Salalah between latitudes 16o 33′N and 22o 21′N and longitude 53o 09′ and 59o 55′ E and from depths of 20 to 250 m respectively. Marginal increment analysis of the sagittal otolith confirmed the deposition of annual increments on transverse sections, validating this technique for age and growth studies. Fish size (Fork Length, FL) ranged between 33–78 cm and age of fish ranged between 2 and 14 years with 5–9 years old fish comprising the majority of the catch. Both males and female exhibited asymptotic patterns of growth and the combined growth curve for both sexes provided von Bertalanffy growth (VBG) parameters of L∞ = 77.2 cm FL (≡83.8 cm Total Length), k = 0.232/y and t0 = −0.058 y. VBG parameters, derived from Length‐Frequency Distribution Analysis (LFA) using ELEFAN1, PROJMAT and SLCA, obtained similar values (average values for the 3 methods: L∞ = 78.8 cm FL, k = 0.35/y and t0 = −0.64 y) to those obtained from otolith analysis. A strong linear relationship was observed between otolith weight and age, and although age residuals ±4 years was observed between sagittal otolith age and estimated age (depending on sex and otolith weight), the results indicated that otolith weight could be used as a rapid proxy to estimate age and derive VBG parameters. In conclusion, both otolith ageing and LFA methods provided similar L∞ and k values and the average values derived from all 4 methods lies within the auximetric plot for the species providing confidence in the VBG parameters obtained for small spotted grunt in the Arabian Sea.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Age and growth validation of the small spotted grunt Pomadasys commersonnii (Lacepède, 1801) from the northwestern coast of the Arabian Sea of Oman

2018

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“…Since the cohorts could not be assumed to represent age classes, perhaps because of continuous reproduction in three taxa, the results could not be used to estimate VBGF parameters or mortality rates (King, 2007). Continuous or prolonged periods of recruitment lead to large variance in length by age and therefore obscure cohorts from young ages on (Pitcher, 2002). Understanding growth, and then mortality, for these taxa will require analysis of hard parts ( e.g.…”

Section: Discussionmentioning

confidence: 99%

“…For each case‐study taxon, both parametric mixture analysis (MIX, Pitcher, 2002) and non‐parametric methods (ELEFAN, SCLA and PROJMAT; Kirkwood et al , 2001) were applied to L T frequency data to estimate VBGF growth parameters: L ∞ (asymptotic length) and k (rate at which the asymptotic size is approached) and Z (total mortality rate). These approaches did not, however, prove profitable with the data.…”

Section: Methodsmentioning

confidence: 99%

Using life‐history information to assess potential effects of shrimp trawling on small fishes

Foster

Vincent

2010

Journal of Fish Biology

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The current study presents information on size distributions, size at recruitment to the fishery, size at maturity and patterns of reproduction for several small benthic fishes caught as by-catch in the southern Gulf of California (Mexico) shrimp trawl fishery: sand perch Diplectrum spp., lumptail searobin Prionotus stephanophrys, bigscale goatfish Pseudupeneus grandisquamis and silver stardrum Stellifer illecebrosus. Pseudupeneus grandisquamis, P. stephanophrys and S. illecebrosus populations were all sexually dimorphic in size. Total-length (L(T))-based analyses did not provide reliable information on survival and growth. The majority of sampled P. grandisquamis and S. illecebrosus were caught before reproductive maturity, whereas the majority of Diplectrum spp. and almost all P. stephanophrys were mature when caught. L(T) at 50% gear retention (L(Tc), mm) v. 50% maturity (L(Tm), mm): Diplectrum spp. 124.53 v. 131.43; P. grandisquamis 90.98 v. 135.20; S. illecebrosus 82.55 v. 137.30. L(Tc) for P. stephanophrys was 104.73, but L(Tm) could not be modelled for this species as almost all captured individuals were mature. Diplectrum spp., P. grandisquamis and S. illecebrosus were indeterminate spawners, whereas P. stephanophrys appeared to be a determinate spawner. Sex ratios were equal for each of the gonochoristic species. In general, the gonado-somatic index (I(G)) increased with increasing L(T) for all except P. stephanophrys, where I(G) decreased with increasing L(T) for both males and females. Mature individuals of all taxa were found throughout the sampling period (September to March), and I(G) increased with sample day for all except females of P. grandisquamis. The current data suggest the potential for fishery effects on sampled populations of P. grandisquamis and S. illecebrosus.

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“…Catchability (Mahon 1980;Anderson 1995) and abundance (Pauly and Moreau 1997;Pitcher 2002) also fluctuate with fish length. The motivations to account for such variabilities within a Bayesian hierarchical model to derive abundance estimates are 3-fold.…”

Section: Introductionmentioning

confidence: 99%

A hierarchical model to estimate the abundance and biomass of salmonids by using removal sampling and biometric data from multiple locations

Ruiz

2010

Can. J. Fish. Aquat. Sci.

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We present a Bayesian hierarchical model to estimate the abundance and the biomass of brown trout ( Salmo trutta fario ) by using removal sampling and biometric data collected at several stream sections. The model accounts for (i) variability of the abundance with fish length (as a distribution mixture), (ii) spatial variability of the abundance, (iii) variability of the catchability with fish length (as a logit regression model), (iv) spatial variability of the catchability, and (v) residual variability of the catchability with fish. Model measured variables are the areas of the stream sections as well as the length and the weight of the caught fish. We first test the model by using a simulated dataset before using a 3-location, 2-removal sampling dataset collected in the field. Fifteen model alternatives are compared with an index of complexity and fit by using the field dataset. The selected model accounts for variability of the abundance with fish length and stream section and variability of the catchability with fish length. By using the selected model, 95% credible interval estimates of the abundances at the three stream sections are (0.46,0.59), (0.90,1.07), and (0.56,0.69) fish/m2. Respective biomass estimates are (9.68, 13.58), (17.22, 22.71), and (12.69, 17.31) g/m2.

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A Bumpy Old Road: Size-Based Methods in Fisheries Assessment

Cited by 9 publications

References 26 publications

Age and growth validation of the small spotted grunt Pomadasys commersonnii (Lacepède, 1801) from the northwestern coast of the Arabian Sea of Oman

Age and growth validation of the small spotted grunt Pomadasys commersonnii (Lacepède, 1801) from the northwestern coast of the Arabian Sea of Oman

Using life‐history information to assess potential effects of shrimp trawling on small fishes

A hierarchical model to estimate the abundance and biomass of salmonids by using removal sampling and biometric data from multiple locations

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