Fisheries Management Research Papers - Academia.edu (original) (raw)

The world’s oceans and coasts are awash in a sea of politics. The marine environment is increasingly busy, changing, and a site of degradation, marginalization, injustice, contestation and conflict over declining resources and occupied... more

The world’s oceans and coasts are awash in a sea of politics. The marine environment is increasingly busy, changing, and a site of degradation, marginalization, injustice, contestation and conflict over declining resources and occupied spaces at local to global scales. Themes of political ecology, such as power and politics, narratives and knowledge, scale and history, environmental justice and equity, are thus salient issues to understand in ocean and coastal governance and management. This subject review examines research on these themes of political ecology in the ocean and coastal environment and reflects on how the insights gained might be applied to governance and management. Political ecology provides important insights into: the influence of power in ocean management and governance processes; the manner in which narratives, knowledge, and scale are used to legitimize and shape policies and management efforts; the effects of historical trajectories on present circumstances, options, and practices; and the nature of inequities and environmental injustices that can occur in the marine environment. Moreover, ocean and coastal researchers, practitioners, and decision makers ought to engage with the political processes and injustices occurring in the ocean. Moving from critical insights to constructive engagements will ensure that political ecology helps to plant seeds of hope in the Anthropocene ocean.

This dissertation examines multiple scales of Indigenous history on the Northwest Coast from the disciplinary perspective of archaeology. I focus on cultural lifeways archaeologically represented in two key domains of human existence:... more

This dissertation examines multiple scales of Indigenous history on the Northwest Coast from the disciplinary perspective of archaeology. I focus on cultural lifeways archaeologically represented in two key domains of human existence: food and settlement. The dissertation consists of six individual case studies that demonstrate the utility of applying multiple spatial and temporal scales to refine archaeological understanding of cultural and historical variability on the Northwest Coast over the Mid-to-Late Holocene (ca. 5,000-200 BP). The first of three regionally scaled analyses presents a coast-wide examination of fisheries data indicating that Pacific herring (Clupea pallasii) exhibit a pervasive and previously under-recognized importance in Northwest Coast Indigenous subsistence practices. Next, I use zooarchaeological data from the southern British Columbia coast to identify a pattern of regional coherence in Coast Salish and Nuu-chah-nulth hunting traditions reflecting the scale of intergenerational cultural practice. The third study re-calibrates the settlement history of a small and historically significant locality in Coast Tsimshian territory (Prince Rupert Harbour) to clarify the temporal resolution of existing radiocarbon datasets and test inferences about social and political change. Following this regional exploration of scale, I document site-specific temporal variability in archaeological fisheries data from a Nuu-chah-nulth ‘big-house’ reflecting climatic and socio-economic change. I examine Indigenous oral histories and archaeological datasets to evaluate these parallel records of settlement in the neighbouring territory of an autonomous Nuu-chah-nulth polity before and during the occupation of a large defensive fortress. Finally, I demonstrate how everyday foodways are archaeologically expressed and reflect ecological differences and active management strategies within several spatially associated sites over millennial timescales. These linked case studies offer new clarity into long-standing debates concerning archaeologically relevant scales of cultural-historical variability on the NWC. They collectively demonstrate an enduring regional and temporal coherence for key aspects of Indigenous resource use and settlement and a historical dynamism at finer scales. I argue this has cultural, historical, and archaeological significance as well as relevance for contemporary understandings of the Northwest Coast environment. I conclude that a focus on the pervasive aspects of the everyday over millennia offers insight into individual actions across broader patterns of history.

The major aim of this article is to examine how migrations affect private governance, taking as a case study the Prud'homie de pêche, a private order that has governed the fishery of Marseille for the past six centuries. Scholarship... more

The major aim of this article is to examine how migrations affect private governance, taking as a case study the Prud'homie de pêche, a private order that has governed the fishery of Marseille for the past six centuries. Scholarship generally argues that social norms guarantee the efficiency of private orders and their ability to resist the arrival of newcomers. My data suggests that the Prud'homie has failed to accommodate social changes prompted by migratory flows, not despite but because of its social norms. This paper suggests that social norms are not only powerful tools of governance for private orders, but also forces of inertia that can prevent these orders from accommodating social changes.

The species diversity, richness and composition of fish communities as well as some physico-chemical conditions were analyzed in order to establish baseline data inventory in three wetland systems in Ghana. Water quality checker was used... more

The species diversity, richness and composition of fish communities as well as some physico-chemical conditions were analyzed in order to establish baseline data inventory in three wetland systems in Ghana. Water quality checker was used to measure five physico-chemical parameters while a pole-seine net was used for fish sampling. Results showed that dissolved oxygen content of Essei lagoon was critically low (averagely 0.7 mg/L) while temperature was significantly higher in Butuah lagoon, with the Whin estuary maintaining moderately good conditions. Twenty-six (26) species of shell-and finfishes belonging to 18 families from freshwater, brackishwater and marine sources were encountered in the water bodies. Whin had the most rich and diverse fish community (d= 3.21, H'= 1.62), followed by Butuah (d= 1.54, H' = 1.56), with Essei recording the least (d= 0.99, H' =1.02). The moderately good environmental conditions, together with the higher richness and diversity of fish biota in the Whin estuary generally reflect a highly productive system that merits management planning and possible conservation status. The lower richness and the correspondingly lower diversity of fish community in the Essei and Butuah Lagoons with most of the fish being juveniles require serious and realistic management interventions to be enforced.

Global climate action plans risk resulting to climate maladaptation and shocks when prudent measures are inapt. Adaptation strategies require multidisciplinary approach from all sectors with periodic monitoring and evaluation which are... more

Global climate action plans risk resulting to climate maladaptation and shocks when prudent measures are inapt. Adaptation strategies require multidisciplinary approach from all sectors with periodic monitoring and evaluation which are carefully planned, locally adaptable and results-oriented. For decades, various governments, development practitioners and international organizations have made concerted efforts in tackling large scale climate events. These stern initiatives forms part of Millennium Sustainable Development Goals (SDGs), specifically SDG 13 meant to combat climate change. The increasing demand for frameworks that effectively monitor and examine the outcomes of these huge investments made by policy-makers across regions have enhanced the evaluation and monitoring of various climate change adaptation strategies. This study sought to assess the effectiveness and sustainability of initiated adaptation strategies. The study used descriptive statistics based on informants’ ...

The carbon (δ13C) and nitrogen (δ15N) values of Sander vitreus scales differed pre and post-introduction in treatment lakes among years following the introduction of Micropterus dolomieu. No difference of δ13C and δ15N in S. vitreus... more

The carbon (δ13C) and nitrogen (δ15N) values of Sander vitreus scales differed pre and post-introduction in treatment lakes among years following the introduction of Micropterus dolomieu. No difference of δ13C and δ15N in S. vitreus scales was found in control lakes where M. dolomieu were not introduced. In treatment lakes, S. vitreus δ15N increased and δ13C decreased. No relationship was found between S. vitreus and M. dolomieu abundance in the two treatment lakes. Size
structure of S. vitreus and M. dolomieu was negatively correlated and condition of the two species was positively correlated. Although S. vitreus feeding habits may have changed in the treatment lakes after M. dolomieu introductions, evidence suggests that fitness-related factors (i.e. abundance and condition) of S. vitreus remained unchanged, indicating S. vitreus and M. dolomieu may coexist
where M. dolomieu have been introduced.

The overall objective of this study was to assess to what extent Macrobrachium rosenbergii culture in reservoir is sustainable and whether it has the potential to provide a livelihood option for reservoir fishers. Fisheries and... more

The overall objective of this study was to assess to what extent Macrobrachium rosenbergii culture in reservoir is sustainable and whether it has the potential to provide a livelihood option for reservoir fishers. Fisheries and socioeconomic data collection were conducted from 2016 January to 2018 December in five perennial reservoirs in the Northern Province of Sri Lanka. Results revealed that culture-based fisheries and the introduction of M. rosenbergii in the five selected reservoirs have achieved considerable success and resulted in significant increases in fish production, income of fishers, availability of fresh fish for the rural communities and livelihood opportunities for fishing families. Socioeconomic factors such as, age, fisheries experience, fish catch of the previous day, market value, household status and livelihood diversification influenced reservoir fishing. Low rainfall, strong wind, high temperature, over-growth of aquatic plants and algal blooms wildlife attacks and theft of fishing gear were identified as key stressors.

There is a growing consumption trend towards sustainability. A feedback between sustainability of consumption and biodiversity maintenance seems a positive trend toward sustainability. The results showed that an index of... more

There is a growing consumption trend towards sustainability. A feedback between sustainability of consumption and biodiversity maintenance seems a positive trend toward sustainability. The results showed that an index of perception of consumers could serve to evaluate the status of the perception about fish resources. This index could be useful for comparing different areas or communities. It could be useful for mapping areas where educational programs could be enforced and detecting population strata where educational attention should be important.

Fisheries ministers squander the economic potential of our seas by consistently fishing over and above the limits recommended by scientists. This is the third in a series of briefings to identify which countries are standing in the way of... more

Fisheries ministers squander the economic potential of our seas by consistently fishing over and above the limits recommended by scientists. This is the third in a series of briefings to identify which countries are standing in the way of more fish, profits and jobs for European citizens.

This meeting, the second national Fisheries Governance Dialogue, aimed to help stakeholders in the fisheries sector generate a shared understanding of critical lessons and pathways for fisheries co-management success in Ghana. This was a... more

This meeting, the second national Fisheries Governance Dialogue, aimed to help stakeholders in the fisheries sector generate a shared understanding of critical lessons and pathways for fisheries co-management success in Ghana. This was a direct response to the call from both fisheries communities and the government of Ghana for a radical change from the way fisheries resources are currently being managed. Indeed, the justification for such a gathering for dialogue was appropriately summed up by the Deputy Minister for Food and Agriculture in Charge of Fisheries, Hon. Nii Amasa Namoale, in many of his opening remarks, such as the following: “The Government recognizes the urgent need to change the way the country is managing fisheries. While in the past anyone was allowed to purchase a boat and fish, this is no longer the reality of the industry and there is a need to address the issue of open access ...” “The Government recognizes the importance of engaging stakeholders in the proces...

Micropterus salmoides is an important fish species for sport fishing activities, condition that has promoted its introduction to different reservoirs in Mexico and worldwide. With the aim to improve its fisheries management, this research... more

Micropterus salmoides is an important fish species for sport fishing activities, condition that has promoted its introduction to different reservoirs in Mexico and worldwide. With the aim to improve its fisheries management, this research dealt with some reproductive aspects of this species in the Gustavo Diaz Ordaz reservoir, where it was studied from August 2008 through March 2011. To this end, we obtained 938 specimens, with gillnets of different sizes, to determine their total length (Lt, in cm), weight (Pt, in g), sex, gonadosomatic index, condition factor, fecundity and size at first maturity. Lt and Pt ranged from 15.9 to 63 cm (37.4 +/- 78.0) and 57 to 4431 g (731.7 +/- 619.0), respectively. The Pt-Lt relationship showed a positive allometric growth, with no significant difference between males and females (F = 0.9955, p = 0.3187). The male: female ratio obtained was 1:0.83. Mass spawning lasted from December to April. Size at first maturity was 33.7 cm and average fecundity...

Lecithocladium angustiovum is identified from the stomach (87.33%) and the intestine (12.67%) of Indonesian short mackerel (Rastrelliger brachysoma). The description includes an elongated body; a mean total length of 1018.84 µm; and an... more

Lecithocladium angustiovum is identified from the stomach (87.33%) and the intestine (12.67%) of Indonesian short mackerel (Rastrelliger brachysoma). The description includes an elongated body; a mean total length of 1018.84 µm; and an ecsoma of 47.52% of the total length. The oral and ventral sucker ratio is 1:0.63, and the pharynx length is 97.42 µm. The sequence results were obtained by 18s rDNA gene sequencing of the 354 basepair (bp) DNA segment, and the mean base composition (%) was 17.7 A; 35.7 T; 29.6 G; and 17.1 C. A phylogenetic tree was constructed to demonstrate the genetic distance between L. angustiovum and sequences from Lecithocladium excisum, Dinurus longisinus, Plerurus digitatus and Lecithochirium caesionis obtained from GenBank.

Precious corals (Coralliidae) have been a part of numerous aspects of human life and culture for several millennia. They differ from reef-building corals and primarily inhabit deep waters. Their characteristics of a slow renewal rate and... more

Precious corals (Coralliidae) have been a part of numerous aspects of human life and culture for several millennia. They differ from reef-building corals and primarily inhabit deep waters. Their characteristics of a slow renewal rate and high commercial value make them a frangible resource that is easily overexploited. Proposals to manage the main species with high commercial value through trade controls and listing in Appendix II were submitted to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in 2007 and 2010. Two of the main arguments for the northern Pacific precious coral CITES proposal were the more than 60% to 80% decline of Corallium secundum and C. sp. nov. in landings since 1980s and lack of proper management. Although both proposals were rejected, they have sparked debates regarding the benefits of managing coral resources through trade controls and fisheries management. In this study, several arguments related to this topic on northern Pacific precious corals are presented, in the following three dimensions: (1) a reconstructed historical landing series from official FAO data and information on the history of coral fishing have scientifically indicated that the substantial decline in landings in the late 1980s was caused by the abandonment of fishing grounds and a shift in the target species; (2) enhanced management plans, which incorporate effective monitoring, control, and surveillance (MCS) measures, have been implemented in the two main countries that fish precious coral; and (3) the influence of socioeconomic factors must be considered when assessing CITES listing applications. Recommendations for achieving sustainable coral resource conservation are also provided.

This interdisciplinary study integrated methods traditionally related to the social or natural sciences to elucidate and evaluate the various socioenvironmental factors affecting the fisheries of Puerto Rico. Using a case study approach,... more

This interdisciplinary study integrated methods traditionally related to the social or natural sciences to elucidate and evaluate the various socioenvironmental factors affecting the fisheries of Puerto Rico. Using a case study approach, this work focused on Puerto Real, Cabo Rojo, in southwest Puerto Rico, which is the most productive landing site on the island. Phenomenological and semi-structured interviews applied to commercial fishermen and other stakeholders, respectively, were used to

Una breve descripción del parásito, su presentación y los posibles tratamientos

We reconstructed the structure of a tropical marine food web and then analyzed it to evaluate how the trophic network could respond to anthropogenic pressures such as the removal of species by fisheries. To reconstruct the... more

We reconstructed the structure of a tropical marine food web and then analyzed it to evaluate how the trophic network could respond to anthropogenic pressures such as the removal of species by fisheries. To reconstruct the presence/absence of predator-prey interactions, we assembled detailed quantitative information from the scientific literature on the stomach contents of 80 predator species (elasmobranchs, teleosts and invertebrates) collected in the Golfo de Tortugas (Colombia) between 1990 and 2009. We tested three conceptual models of network structure (random, small-world, and scale-free), characterized by different system properties and tolerance to perturbations, to evaluate which one better fitted the reconstructed food web. Our results suggest that this network has small-world structure and scale-free properties. An impact on one species may therefore spread to many species through short interaction chains; only a few nodes with high centrality values would support the network structure. However, contrary to current theory, our analysis revealed no clear relationships between species with high centrality and the large-scale structural patterns observed in the network (small-world and scale-free properties). This observation indicates that ecosystem-based fisheries management should prioritize not only high-centrality species (e.g., shrimps, which furthermore are species of high commercial value in the area), but should also consider species with unique structural properties such as those with little or no topological redundancy such as large sharks. For this reason, top predator conservation needs more attention than currently received in fisheries management.

Investigations into population structure have been at the forefront of fisheries research for decades, yet it is generally ignored in stock assessmentmodels. As the complex nature ofmarine population structure has been uncovered, models... more

Investigations into population structure have been at the forefront of fisheries research for decades, yet it is generally ignored
in stock assessmentmodels. As the complex nature ofmarine population structure has been uncovered, models have attempted
to accurately portray it through the development of spatially explicit assessments that allow for movement between subpopulations.
Although current tag-integrated movement models are highly complex, many arose from the relatively simple
models of Beverton and Holt (1957). This article traces the historical development of these models and compares their
features. Originally estimation of movement utilized only tag-recapture models, but now tag-integrated assessment models
incorporate several sources of fishery, survey, and tag-recapture information to inform movement estimates. As spatial
management measures become more widely used, it is increasingly important that assessment models include the spatial
complexities of population structure and patterns of fishery removals, in order for more reliable monitoring of population
rebuilding to take place. A generalized metapopulation model is proposed for use in fisheries stock assessment, which allows
for adult movement among spatially discrete sub-populations. The input requirements for the model include region-specific
catch-at-age, a tag-recapture dataset, and auxiliary information, such as a fishery-independent abundance index.

This study was carried out in Beki river, for the period of seven months in 2014. Through profilistic study, we were evaluate the socio-economic condition of fishermen and their different kinds of fishing gears. A total sample of... more

This study was carried out in Beki river, for the period of seven months in 2014. Through profilistic study, we were evaluate the socio-economic condition of fishermen and their different kinds of fishing gears. A total sample of respondents was 276 fishermen. The result of the study revealed that most of the responded belonged to the Muslim community (68.48%). Illiteracy was found one of the major problem of the studied area as about 72.10% respondents were found to be illiterate. Here, fishing business was totally male dominated (97.10%) and maximum (90.22%) fishermen had married. About 49.28% of total respondents were found to belong under the age group between 31-40 years. About 52.17% respondents working as farmer for other earning apart from fishing. Various kinds of fishing gear were used in Beki River for fishing, viz., Cast nets, Scoop nets, Gill nets, Fishing lines and Traditional Bamboo Trap.

The San Francisco Estuary (SFE) is heavily influenced by anthropogenic activities, including historic and chronic contaminant inputs. These contaminants can adversely affect SFE fish populations, particularly white sturgeon, because they... more

The San Francisco Estuary (SFE) is heavily
influenced by anthropogenic activities, including historic
and chronic contaminant inputs. These contaminants can
adversely affect SFE fish populations, particularly white
sturgeon, because they are a benthic dwelling, long-lived
species. We measured a suite of metals and organic contaminants
in liver and gonad tissues of 25 male and 32
female white sturgeon as well as several physiological
indicators of sturgeon health. Most sturgeon (68% of males
and 83% of females) were estimated to be between 13 and
17 years of age. Sturgeon tissues had elevated concentrations
of several metals, including As, Ba, Cd, Cu, Cr, Pb,
Hg, Ni, Se, and Zn. The most frequently detected organic
contaminants in sturgeon livers and gonads were DDE,
PCBs, PBDEs, and galaxolide. Selenium was detected at
levels similar to those shown to cause impaired liver
physiology and reproductive success in white sturgeon.
Observed Hg levels were higher than those shown to result
in lower condition factor and gonadosomatic indices in
white sturgeon. Liver galaxolide levels correlated with
decreased plasma estradiol levels in female sturgeon. The
Cd, As, and Cu warrant further investigation, because they
were detected at levels known to impair fish health. Our
results suggest contaminants are negatively affecting SFE
white sturgeon health and fitness. Future SFE white sturgeon
contaminant research is suggested.

The study measures the relationship between physicochemical variables with the cell density of phytoplankton in different stages of pond – nursery ponds, grow out ponds and brood stock ponds. The study was conducted on nine fish ponds as... more

The study measures the relationship between physicochemical variables with the cell density of phytoplankton in different stages of pond – nursery ponds, grow out ponds and brood stock ponds. The study was conducted on nine fish ponds as three from each category of pond at Natore Government Fish Farm in Bangladesh, during the months of January to June in 2012. The observed physicochemical variables– water temperature, transparency, dissolved oxygen, pH, ammonia-nitrogen, total alkalinity and total hardness – were found within the standard ranges. Four groups of phytoplankton– Bacillariophyceae, Chlorophyceae, Cyanophyceae and Euglenophyceae– werefound among the ponds where Euglenophyceae was recorded highest number almost in all ponds over the study period. Total abundance of different groups of phytoplankton was recorded as mean (±SD) cell density (cell/l) 62.77±2.16×104, 47.22±0.69×104, and 77.12±3.42×104 in nursery pond, grow out pond and brood stock pond, respectively. Overall phytoplankton was found better in brood stock pond than others. Total phytoplankton density has been exhibited significantly positive correlation with DO and inverse relation with water temperature, pH, ammonia-nitrogen and total alkalinity in case of nursery pond. In case of grow out pond, total phytoplankton density has been exhibited significantly positive correlation with temperature and transparency, and significantly negative correlation with others physicochemical characteristics. In case of brood stock pond, total phytoplankton density has no significant relationship with any physicochemical variables of water.

Following aquarium releases, invasive lionfishes have colonized large areas of the Caribbean and western Atlantic, resulting in an immense ecological damage. The early stages of that invasion are poorly known. Indeed, a lag of time... more

Following aquarium releases, invasive lionfishes have colonized large areas of the Caribbean and western Atlantic, resulting in an immense ecological damage. The early stages of that invasion are poorly known. Indeed, a lag of time between the introduction and detection often preclude genetic characterization of that crucial phase. With elevated awareness, the recent invasion of Pterois miles was quickly detected in the Mediterranean Sea. We hereby show that the very first individuals establishing populations in the Mediterranean Sea display haplotypes that nest within the large genetic diversity of Red Sea individuals, thus indicating an invasion via the Suez Canal. We also show that only two haplotypes are detected in the Mediterranean Sea, suggesting that few individuals may have been involved in the invasion. Thus, we conclude that the Mediterranean invasion is the result of a movement of individuals from the Red Sea, rather than from other means, and that low genetic diversity ...

Abstract Recent studies have shown that coastal and shelf cephalopod populations have increased globally over the last six decades. Although cephalopod landings are dominated by the squid fishery, which represents nearly 80% of the... more

Abstract Recent studies have shown that coastal and shelf cephalopod populations have increased globally over the last six decades. Although cephalopod landings are dominated by the squid fishery, which represents nearly 80% of the worldwide cephalopod catches, octopuses and cuttlefishes represent ∼10% each. Total reported global production of octopuses over the past three decades indicates a relatively steady increase in catch, almost doubling from 179,042 t in 1980 to 355,239 t in 2014. Octopus fisheries are likely to continue to grow in importance and magnitude as many finfish stocks are either fully or over-exploited. More than twenty described octopus species are harvested from some 90 countries worldwide. The current review describes the major octopus fisheries around the globe, providing an overview of species targeted, ecological and biological features of exploited stocks, catches and the key aspects of management.

Population parameters for Red Pandora, Pagellus bellottii (Steindachner, 1882) from the eastern coastline of Ghana, using length-frequency data from June 2014 to January 2015 were assessed. A total of 440 samples of Pagellus bellottii... more

Population parameters for Red Pandora, Pagellus bellottii (Steindachner, 1882) from the eastern coastline of Ghana, using length-frequency data from June 2014 to January 2015 were assessed. A total of 440 samples of Pagellus bellottii were measured for standard length and analyzed with FiSAT II. The asymptotic length (L ∞) and growth rate (K) were 19.43 cm and 0.42 per year. Theoretical age at birth (t 0) and growth performance index (ϕ) were-0.44 per year and 2.20. The age at first maturity (tm 50) and longevity (t max) were 2.2 years and 7 years. The Bhattacharya's method revealed three modal lengths groups: 9.3 cm, 12.1 cm, and 14.6 cm. Total mortality rate (Z), natural mortality rate (M) and fishing mortality rate (F) were 2.58 per year, 1.10 per year, and 1.48 per year. Exploitation rate (E current) and maximum exploitation rate (E max) were estimated as 0.57 and 0.93 respectively. The recruitment pattern was continuous with two major recruitment pulses. VPA outcome showed that mid-lengths of 11.5 cm and 12.5 cm experienced the highest harvesting rate. The fishing regime of Pagellus bellottii fell in the developed stage based on the quadrant rule. Maximum Sustainable Yield (MSY) was 7864.18 tons. Results from the study indicated the existence of growth overfishing with the present state of exploitation as a forewarning to the collapse of the fishery in future. With resilience of Red pandora within the medium category, incidence of overfishing will produce economic consequences. The developed stage of fishing suggested that maximization of yield per recruits will lead to low stock biomass of Red pandora.

The relationships between size (length and width) of the lagenar (asteriscus) and the utricular (lapillus) otoliths and body length for five cyprinid fish species, freshwater bream Abramis brama, white bream Blicca bjoerkna, Prussian carp... more

The relationships between size (length and width) of the lagenar (asteriscus) and the utricular (lapillus) otoliths and body
length for five cyprinid fish species, freshwater bream Abramis brama, white bream Blicca bjoerkna, Prussian carp Carassius gibelio, brond-snout Chondrostoma regium, and rudd Scardinius erythrophthalmus, collected from Lake Ladik from November 2009 through
October 2010, are presented. The right and left side measurements of otoliths were pooled in all cases except asteriscus length in
Prussian carp. Nonlinear and linear functions provided the best fit for 80% and 20% of all species, respectively. All relationships were
highly significant (P < 0.001, R2 > 0.71) and the mean percent prediction errors were less than 10%. The results showed that reliable
original size estimates of all species studied are obtainable from their otolith biometrics. The regressions from this study can be useful for investigators examining food habits of piscivorous fauna and sizes of these fishes in archaeological samples.

The common cuttlefish (Sepia officinalis) is an important commercial resource and one of the most appreciated cephalopod in the Egyptian Mediterranean waters. It is a target species for the trawl fishery in Port Said fishing ground... more

The common cuttlefish (Sepia officinalis) is an important commercial resource and one of the most appreciated cephalopod in the Egyptian Mediterranean waters. It is a target species for the trawl fishery in Port Said fishing ground contributing about 10% of the total annual landings. The stock of Sepia officinalis in the southeastern Mediterranean (Port Said waters) has been assessed using a three years length frequency data (2008-2010) collected monthly from the trawl fishery at the fishing harbor of Port Said city. By applying the Y/R analysis on the pseudo-cohort 2008-2010 using the VIT program, it is noticed that this stock is over exploited, being the fishery operating below the optimal yield level since the current Y/R is lower than the maximum. Results suggest a decreasing trend in the average fishing mortality along the studied period by about 30-40%.

Aim This study investigated the use of stable δ13C and δ18O isotopes in the sagittal otolith carbonate of narrow-barred Spanish mackerel, Scomberomorus commerson, as indicators of population structure across Australia.Location Samples... more

Aim This study investigated the use of stable δ13C and δ18O isotopes in the sagittal otolith carbonate of narrow-barred Spanish mackerel, Scomberomorus commerson, as indicators of population structure across Australia.Location Samples were collected from 25 locations extending from the lower west coast of Western Australia (30°), across northern Australian waters, and to the east coast of Australia (18°) covering a coastline length of approximately 9500 km, including samples from Indonesia.Methods The stable δ13C and δ18O isotopes in the sagittal otolith carbonate of S. commerson were analysed using standard mass spectrometric techniques. The isotope ratios across northern Australian subregions were subjected to an agglomerative hierarchical cluster analysis to define subregions. Isotope ratios within each of the subregions were compared to assess population structure across Australia.Results Cluster analysis separated samples into four subregions: central Western Australia, north Western Australia, northern Australia and the Gulf of Carpentaria and eastern Australia. Isotope signatures for fish from a number of sampling sites from across Australia and Indonesia were significantly different, indicating population separation. No significant differences were found in otolith isotope ratios between sampling times (no temporal variation).Main conclusions Significant differences in the isotopic signatures of S. commerson demonstrate that there is unlikely to be any substantial movement of fish among these spatially discrete adult assemblages. The lack of temporal variation among otolith isotope ratios indicates that S. commerson populations do not undergo longshore spatial shifts in distribution during their life history. The temporal persistence of spatially explicit stable isotopic signatures indicates that, at these spatial scales, the population units sampled comprise functionally distinct management units or separate ‘stocks’ for many of the purposes of fisheries management. The spatial subdivision evident among populations of S. commerson across northern and western Australia indicates that it may be advantageous to consider S. commerson population dynamics and fisheries management from a metapopulation perspective (at least at the regional level).