Assessing abundance and catch selectivity of Octopus cyanea by the artisanal fishery in Lakshadweep islands, India

2018 ◽  
Vol 31 ◽  
pp. 10 ◽  
Author(s):  
Aditi Nair ◽  
Sutirtha Dutta ◽  
Deepak Apte ◽  
Balasaheb Kulkarni
Keyword(s):  
Sex Ratio ◽  
Stock Assessment ◽  
Fishing Effort ◽  
Local Economy ◽  
Fishing Activity ◽  
Island States ◽  
Juvenile Abundance ◽  
Long Time ◽  
Female Bias ◽  
Lakshadweep Islands

Subsistence fishery for cephalopods contributes significantly to the local economy of several Asian, African and island states. In addition to being unregulated and undocumented, recent studies indicate that low-scale fisheries can have detrimental effects on marine ecosystems. In the Lakshadweep islands, men, women and children have been involved in spear fishing for octopus for a long time, but there is a paucity of information on the biology and fishery of the octopus species in Indian waters. In this study, we estimated the population abundance, morphometry and sex ratio of Octopus cyanea. Moreover, we examined whether the current octopus spear fishing activity displayed size or sex selectivity, given that larger individuals are easier to spot and brooding females spend more time in crevices. O. cyanea surveys were conducted by snorkeling in the lagoons of Kavaratti and Agatti islands between November 2008 and April 2012. The estimated mean density of O. cyanea was 3 and 2.5 individuals per hectare in Agatti and Kavaratti, respectively. Individual mean weight was 923.36 g and 846.26 g in Agatti and Kavaratti and the male:female sex ratio 1.35:1 and 3.8:1, respectively. Comparison between visual counts and fisheries landings indicated that fishing effort was concentrated in areas of high juvenile abundance but without female-bias. Constructing a long-term database of fishery catches will help with stock assessment and understanding the factors that influence octopus populations. Implementation of a lower size limit of 500 g would act as a precautionary measure against catching very small octopuses.

scholarly journals TIPE PERIKANAN DAN STATUS SUMBERDAYA IKAN TERUBUK (Tenualosa macrura, Bleeker 1852), DI PERAIRAN ESTUARIN BENGKALIS DAN SELAT PANJANG

2018 ◽  
Vol 23 (4) ◽  
pp. 261
Author(s):  
Suwarso Suwarso ◽  
Muhammad Taufik ◽  
Akhmad Zamroni
Keyword(s):  
Sex Ratio ◽  
Species Conservation ◽  
Fishing Effort ◽  
Conservation Area ◽  
Gill Net ◽  
Spawning Stock ◽  
The Status ◽  
Long Time ◽  
Protandrous Hermaphrodite ◽  
Average Size

Ikan terubuk (Tenualosa spp.) adalah ikan estuarin bersifat ‘protandrous hermaphrodite’ dan endemik di estuarin sekitar Bengkalis. Jenis Tenualosa macrura ditemukan di sekitar Bengkalis (Riau), jenis T. ilisha di sekitar Labuhan Batu dan Labuhan Bilik (Sumatra Utara), sedangkan T. toli ditemukan di perairan pantai barat Pemangkat (Kalbar). Sumber daya terubuk di sekitar Bengkalis saat ini sangat menurun akibat eksploitasi dan recruitment overfishing meskipun pembatasan penangkapan telah diterapkan. Tulisan ini membahas status sumber daya ikan terubuk di sekitar Bengkalis dan Selat Panjang berdasarkan data monitoring hasil tangkapan periode 2014-2016 dan observasi lapangan selama 2015-2016. Ikan terubuk merupakan ikan dominan dari enam jenis hasil tangkapan pada gill net, jumlahnya sekitar 15% dari total hasil tangkapan, upaya penangkapan tergolong intensif sehingga penurunan upaya yang dilakukan ternyata kurang signifikan, bahkan pada saat close season dan close area (September sampai November) upaya penangkapan cenderung tinggi. Kondisi ini tentu tidak sesuai dengan tujuan perlindungan terbatas dan konservasi jenis yang diterapkan. Penurunan populasi terubuk tampak nyata dalam bentuk hasil tangkapan (CPUE), sex ratio maupun produksi pendaratan. Ikan kategori “Pias” (ikan jantan) tetap dominan dan semakin banyak, sebaliknya kategori “Terubuk” (ikan betina matang gonad) semakin sedikit, artinya ukuran rata-rata ikan juga semakin kecil. Keberadaan populasi ikan terubuk di sekitar P. Tiga (Kab. Kepulauan Meranti) dengan kondisi matang gonad dan secara genetik memiliki pola DNA yang sama dengan yang berada di Bengkalis. Perluasan daerah konservasi dan perlindungan terbatas terhadap stok-stok tersebut disarankan.The terubuk (Tenualosa spp) or shads, is a estuarine and endemic ‘protandrous hermaphrodite’ fish species. Species Tenualosa macrura is found in estuarine waters around Bengkalis (Riau Province), T. ilisha around Labuhan Batu and Labuhan Bilik (North Sumatera Province) while T. toli in west coast of Pemangkat (West Kalimantan Province). The terubuk reosurce in Bengkalis water is heavily degraded due to high exploitation and recruitment overfishing eventhough fishing limitation is applied. This paper is discussing the status of terubuk/longtail shad (Tenualosa macrura) resources in Bengkalis estuarine and Selat Panjang waters (Kabupaten Kepulauan Meranti) base on data of 2014-2016 catch monitoring data and field observation during 2015-2016. Terubuk is one of 6 dominant catches from gillnet, contributing about 15% of all catch. The fishing effort was so intensive even though management measure is applied to reduce its exploitation. During the close season when fishing on terubuk is banned (in September to November) as well as the ban in close area , the fishing effort has been still high. This condition is not in line with the objective of protecting the terubuk resources. Therefore, this condition must be changed and returned to objective of “limited protection” and “species conservation” by adopting a more strict rule on limiting fishing effort on terubuk through an evaluation. The decreasing of terubuk population can be seen from CPUE, sex ratio and also in landing, short time (2012 – 2016) and long time (18 years). In overall, the “Pias” (adult male) individuals remainned dominant and wereeven getting more in number, while the “Terubuk” (adult female) on the contrary, which means that the average size of actual fish cought was getting smaller. The existence of terubuk population around Pulau Tiga (Kabupaten Kepulauan Meranti) with mature gonad would share the same genetic pattern with population from Bengkalis. This explaines the connectivity between two stocks, at least there might be another spawning stock other than Bengkalis’s. The expand of the conservation area and limited protection on those stocks is highly recommended.

Fecundity and Gonado-somatic Index of Trichiurus lepturus (Linnaeus, 1758) Along the Zamboanga del Norte Coast

2018 ◽  
Vol 6 (7) ◽  
pp. 120
Author(s):  
Ma. Dulce C. Guillena
Keyword(s):  
Sex Ratio ◽  
Stock Assessment ◽  
Chi Square ◽  
Moon Phases ◽  
Ovary Weight ◽  
Moment Coefficient ◽  
Trichiurus Lepturus ◽  
Significant Difference ◽  
The Relationship ◽  
Somatic Index

Gonado-somatic index and fecundity are tools for measuring the sexual maturity and ability of animals to reproduce.  This study investigates the reproduction of Trichiurus lepturus. Specifically, this aimed to determine the sex ratio, the GSI, the relationship between fecundity and total length, fecundity and total weight, fecundity and ovary weight. The Descriptive Method of research was used.  Percentage and chi-square was utilized in determining the percentage of occurrence and sex ratio respectively.   Pearson r Product Moment Coefficient of Correlation was used to determine the relationships of the parameters. The study revealed that females outnumbered males and the sex ratio for different month showed significant difference.  Spawning season was observed to occur in November and December as revealed in its GSI values and it synchronized with the full and new moon phases.  Fecundity is positively correlated with body weight, body size, and ovary weight where ovary weight is observed to be the best index for fecundity.  The results of this study could be used further for formal stock assessment of cutlassfish fishery.

scholarly journals Assessing the Potential of Catch-Only Models to Inform on the State of Global Fisheries and the UN’s SDGs

2021 ◽  
Vol 13 (11) ◽  
pp. 6101
Author(s):  
Rishi Sharma ◽  
Henning Winker ◽  
Polina Levontin ◽  
Laurence Kell ◽  
Dan Ovando ◽  
...  
Keyword(s):  
Stock Assessment ◽  
Fishing Effort ◽  
The State ◽  
Sources Of Information ◽  
Ongoing Research ◽  
Traditional Assessment ◽  
Stock Status ◽  
Stock Assessments ◽  
Recent Developments ◽  
Measure Of Performance

Catch-only models (COMs) have been the focus of ongoing research into data-poor stock assessment methods. Two of the most recent models that are especially promising are (i) CMSY+, the latest refined version of CMSY that has progressed from Catch-MSY, and (ii) SRA+ (Stock Reduction Analysis Plus) a recent developments in field. Comparing COMs and evaluating their relative performance is essential for determining the state of regional and global fisheries that may be lacking necessary data that would be required to run traditional assessment models. In this paper we interrogate how performance of COMs can be improved by incorporating additional sources of information. We evaluate the performance of COMs on a dataset of 48 data-rich ICES (International Council for the Exploration of Seas) stock assessments. As one measure of performance, we consider the ability of the model to correctly classify stock status using FAO’s 3-tier classification that is also used for reporting on sustainable development goals to the UN. Both COMs showed notable bias when run with their inbuilt default heuristics, but as the quality of prior information increased, classification rates for the terminal year improved substantially. We conclude that although further COM refinements show some potential, most promising is the ongoing research into developing biomass or fishing effort priors for COMs in order to be able to reliably track stock status for the majority of the world’s fisheries currently lacking stock assessments.

scholarly journals Sustainable exploitation of temperate fish stocks

2009 ◽  
Vol 6 (1) ◽  
pp. 124-127 ◽  
Author(s):  
Henrik Sparholt ◽  
Robin M. Cook
Keyword(s):  
Species Interactions ◽  
Fishery Management ◽  
Regional Scale ◽  
Single Species ◽  
Fishing Effort ◽  
Theoretical Concept ◽  
Maximum Sustainable Yield ◽  
Production Model ◽  
The Status ◽  
Long Time

The theory of maximum sustainable yield (MSY) underpins many fishery management regimes and is applied principally as a single species concept. Using a simple dynamic biomass production model we show that MSY can be identified from a long time series of multi-stock data at a regional scale in the presence of species interactions and environmental change. It suggests that MSY is robust and calculable in a multispecies environment, offering a realistic reference point for fishery management. Furthermore, the demonstration of the existence of MSY shows that it is more than a purely theoretical concept. There has been an improvement in the status of stocks in the Northeast Atlantic, but our analysis suggests further reductions in fishing effort would improve long-term yields.

Exploitation status and stock assessment by pseudo-cohort analysis of the bluefish, Pomatomus saltatrix, in the Gulf of Gabes (Tunisia)

2007 ◽  
Vol 87 (5) ◽  
pp. 1315-1319 ◽  
Author(s):  
Khalifa Dhieb ◽  
Mohamed Ghorbel ◽  
Othman Jarboui ◽  
Abderrahmen Bouaïn
Keyword(s):  
Stock Assessment ◽  
Cohort Analysis ◽  
Fishing Effort ◽  
Individual Growth ◽  
Eastern Coast ◽  
Pomatomus Saltatrix ◽  
Gulf Of Gabes ◽  
Gulf Of Gabès ◽  
Exploitation Status ◽  
The One

The bluefish, Pomatomus saltatrix, is quite abundant in the Gulf of Gabes, off the south-eastern coast of Tunisia. It is commercially exploited by artisanal gears and trawlers all year round, and by purse seine nets from May to August (bluefish fishery season). Catches of bluefish, in the period 1996–2004 fluctuated between 365.6 t and 1240.1 t with an annual average of 805 t. This fluctuation, partially due to the migratory nature of the species, could be also attributed to the fleet activities that sometimes changed at the mercy of the operators. The analysis of the virtual population of bluefish in the Gulf of Gabes showed that, in 2002, the stock that had just recovered rightly after an excessive fishing in 1996–1997 was again subject to a fishing effort that passed its capacity (E=0.71; E>0.5). The biomass (B) estimated to be ~2178.9 t only tolerated the extraction of 713.4 t (more or less one-third of B). However, the three fleets in use removed 1029.1 t with a yield per recruit (Y/R) of 70.5 g. As a result of this over-fishing, the actual stock of bluefish in the Gulf of Gabes was characterized by individuals having a mean total length of 17.88 cm, a size which is much lower than the one at first sexual maturity (23.5 cm). The turnover (D/B) being of 75.23%, it did not allow the reconstitution of the stock. The total removals (~1639 t) due to both natural mortality (M=0.28) and fishing mortality (F=0.675) had to be compensated especially by individual growth (1534.2 t; 93.6%) because of the low weight of the recruits.

scholarly journals Influencia de la proporción sexual y del ambiente en la tasa de crecimiento poblacional de Callinectes bellicosus (Decapoda: Portunidae) del Golfo de California

2016 ◽  
Vol 64 (3) ◽  
Author(s):  
Demetrio Angel Rodríguez-Felix ◽  
Miguel Angel Cisneros-Mata ◽  
Eugenio Alberto Aragón-Noriega ◽  
José Alfredo Arreola-Lizárraga
Keyword(s):  
Sex Ratio ◽  
Gulf Of California ◽  
Sensitivity Analyses ◽  
Swimming Crab ◽  
Linear Regression Models ◽  
Habitat Size ◽  
Positive Dependence ◽  
Fishing Activity ◽  
Important Species ◽  
Spawning Period

The brown swimming crab (Callinectes bellicosus) is an economically important species in the Gulf of California, and its fishing activity, held in Sonora from 1986, has been affected by a 20-year declining trend in its biomass. With the aim to understand the possible reasons of this species population changes along time, we estimated population growth rate (r) and sex ratio of C. bellicosus, and combined them with three parameters describing its habitat: sea temperature, wetland extension and habitat size in four areas along the coast of Sonora. For this, monthly mean sex ratio was estimated from crabs samples obtained from commercial catches during 1998-2002 and 2012; mean sea surface temperature for the spawning period (May-August) were derived from remote sensors for the same years; while wetland coverages were obtained from published reports, and habitat size was estimated as the fishing surface. For each area, r was estimated using a method developed for limited data situations using commercial landings (t) from 1986-2013. With data from the four areas, simple and multiple linear regression models were developed to ascertain theoretical sensitivities of r to variations in sex ratio and environmental parameters. A total of 24 556 crabs were sampled; males dominated (68.8 %) over females during the study period and in all areas; a cluster analysis identified two groups according to sex ratio: a Northern group with zones 1 and 2, and a Southern group with zones 3 and 4. r values were different in all zones (P<0.001) as was sex ratio (P=0.037); no differences in temperature were identified within the study years (P>0.995). Both the estimated data and sensitivity analyses suggest the existence of a direct and positive dependence of r on the proportion of female crabs and wetland size. We hypothesize that excess fishing of females caused the declining biomass trend of the brown swimming crab in Sonora, and concluded on the convenience of implementing harvest refugia inside coastal wetlands to protect females during the spawning season. 

The Method of Forecasting the Population of Chinese Population Attractive Cities

2013 ◽  
Vol 295-298 ◽  
pp. 2654-2659 ◽  
Author(s):  
Shu Hao Jiao
Keyword(s):  
Chinese Population ◽  
Local Population ◽  
Local Economy ◽  
Floating Population ◽  
Leslie Matrix ◽  
The People ◽  
Population Forecasting ◽  
Long Time ◽  
The City ◽  
Male To Female

This paper presents a method of forecasting the population of Chinese population attractive cities. In this model the overall population is divided into two main parts, floating population(the people who will live in the city for a long time but do not have household register) and local population. The increment of floating population is positively correlated with the increment of local GDP approximately. Leslie matrix is used to imitate the process of the local population growth. Four main factors, death rate, birth rate, the ratio of male to female, and the growth of the local economy are considered to forecast the local population and floating population separately. The method in this paper overcome these shortcomings of the former method that they cannot explain the inner changes of the population, and ignore the factor of migration. So this method will offer a basis for the science of population forecasting.

scholarly journals Short-term stock assessment of Loligo gahi at the Falkland Islands: sequential use of stochastic biomass projection and stock depletion models

2006 ◽  
Vol 64 (1) ◽  
pp. 3-17 ◽  
Author(s):  
Rubén Roa-Ureta ◽  
Alexander I. Arkhipkin
Keyword(s):  
Sex Ratio ◽  
Stock Assessment ◽  
Scaling Factor ◽  
Falkland Islands ◽  
Short Term ◽  
Projection Model ◽  
Biomass Estimate ◽  
Projected Length ◽  
Spatio Temporal ◽  
Stock Depletion

Abstract Roa-Ureta, R. and Arkhipkin, A. I. 2007. Short-term stock assessment of Loligo gahi at the Falkland Islands: sequential use of stochastic biomass projection and stock depletion models – ICES Journal of Marine Science, 64, 3–17. Two short-term stock assessment models are combined to examine the pre-season, in-season, and post-season dynamics of the Loligo gahi fishery off the Falkland Islands over four consecutive fishing seasons. A stochastic biomass projection model (SBPM) projects a pre-season survey-based biomass estimate from the date of the survey to the start of the season. A stock depletion model (SDM) assesses in-season biomass from commercial daily catch-and-effort data. The SBPM projects the SDM biomass estimate at the end of the season to a post-season date of spawning. Combining the SBPM and the SDM helps to clarify the spatio-temporal functioning of the stock and to assess the comparability of survey- and fishery-based estimates of biomass. For the first 2005 season, projected length frequencies indicate two pulses of recruitment onto the fishing grounds. Survey-based projections of biomass were lower than equivalent fishery-based estimates. Over two surveys, the sex ratio was balanced, suggesting full recruitment of both sexes onto the fishing grounds, and the ratio of survey-projected to fishing-estimated biomass was constant. This constant is interpreted as a scaling factor between survey biomass and absolute biomass.

Grenadiers of the World Oceans: Biology, Stock Assessment, and Fisheries

2008 ◽  
Keyword(s):  
Stock Assessment ◽  
Average Length ◽  
Total Body Length ◽  
Fishing Effort ◽  
Long Distance ◽  
Northwest Atlantic ◽  
Northeast Atlantic ◽  
The North ◽  
Mid Atlantic Ridge ◽  
Total Body

<em>Abstract</em>.—Total body length of roundnose grenadier <em>Coryphaenoides rupestris </em>reaches 123 cm at maximum observed age of 30 years. In the Northwest Atlantic, predominating length is 50–70 cm, in the area of Mid-Atlantic Ridge and off Europe, 50–90 cm. Average length at maturity is 76 cm. Main spawning takes place in the Northeast Atlantic in summer-autumn. Mean fecundity is 30,000 eggs. Grenadier occur mainly near the bottom, but somtimes in the pelagic layer. Vertical migrations are very variable. Long distance horizontal migrations of adults have not been recorded. There is no consensus about population structure. In the Northwest Atlantic the greatest catch (83,700 t) was taken in 1971. Since then the fishery declined until it was stopped completely. On the Mid-Atlantic Ridge, the maximum catch (29,900 t) was taken in 1973, after which catches decreased. In the last 15 years, in the European waters, catches increased and reached 28,900 t in 2004. In the majority of the areas the stock size is at the low level. In the Northeast Atlantic (including the Mid-Atlantic Ridge) the fishery is regulated by NEAFC by the restriction of fishing effort and closed areas. In the Northwest Atlantic, directed fishery is banned by NAFO. In the North Atlantic, in the whole fishing period, the international catch amounted to about 1,000,000 t.

Size-dependent seasonal activity for males of the dung beetle Copris acutidens (Coleoptera: Scarabaeidae)

2019 ◽  
Vol 151 (6) ◽  
pp. 757-767 ◽  
Author(s):  
Mayumi Akamine
Keyword(s):  
Body Size ◽  
Sex Ratio ◽  
Dung Beetle ◽  
Threshold Value ◽  
Reproductive Period ◽  
Seasonal Activity ◽  
Size Dependent ◽  
Horn Length ◽  
Female Bias ◽  
Early Activity

AbstractThis study aimed to determine differences in activities between two male morphs of the dung beetle Copris acutidens Motschulsky (Coleoptera: Scarabaeidae) during the reproductive period and to examine the size distribution of reproductive males that stayed in nests. The activities of two male morphs distinguished by a threshold value of body size were compared with those by horn length. Regardless of body size or horn length, earlier activity of minor males was observed during the reproductive period. The sex ratio showed the greatest female bias when minor males were the more abundant than major males, indicating that minor males were the most active when competition was the weakest and these could avoid direct combat with major males. In morphs distinguished by horn length, more major males than minor males stayed in nests with females although the major males became the most active from the middle of the reproductive period. Thus, longer horns may directly confer a competitive advantage to males, enabling them to stay in nests with females, whereas early activity of minor males does not always indicate the effect of horn length directly. Therefore, this behaviour may occur regardless of whether the morphs differ in body size or horn length.

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