Assessment Of Fishery Resources Research Articles

Validating RAPFISH sustainability indicators: Focus on multi-disciplinary aspects of Indian marine fisheries

In determining the importance of fisheries sustainability indicators, stakeholders’ interest plays a defining role in the fisheries management practices. The indicator based tools such as RAPFISH have been available for sustainability assessment of fishery resources. In the present study, procedures to validate the pre-selected RAPFISH, which is a multidisciplinary indicator based evaluation tool for measuring the sustainability of fishery resources, are applied. The sustainability indicators were subjected to validation process based on feedback from resource owners, users and experts, using Multi-Criteria Analyses such as Weighted Sum Model and Analytic Hierarchy Process. Based on the validation results, suggestions have been made to improve methodology and its effective application in practice. This paper demonstrates RAPFISH as a potentially effective multidisciplinary tool for evaluation of sustainability of fishery resources.

Current fishing practices may induce low risk of sperm limitation in female swimming crab Portunus trituberculatus in the East China Sea

Potential sperm limitation of the swimming crab Portunus trituberculatus was exam- ined during the reproductive season from September 2006 to April 2007 in the East China Sea. We documented developmental variations between the spermatheca and ovary and distinguished these into 5 stages. We counted the number of stored sperm in paired spermathecae and found that more than 50% of sperm initially received during mating disappeared as the sperm plug degenerated; around 1.70 × 10 8 were used for final fertilization, and there was significant correla- tion between the final number of stored sperm and female carapace width. Lastly, using knowl- edge of the reproductive characteristics of P. trituberculatus, we calculated potential sperm:egg ratios of 221:1 or 153:1 for the first brood, and 55:1 or 38:1 for lifetime broods—either from the per- spective of a fishery resource assessment or from the perspective of seed production. From com- parison to sperm:egg ratios of Callinectes sapidus (for lifetime broods this ranges from 10:1 to 42:1), we can infer that female P. trituberculatus in the East China Sea may be at low risk of sperm limitation under current fishing practices. This may be the result of greater fishing mortality of females, causing an increase in the operational sex ratio. The present study improves our knowl- edge of sperm limitation in brachyurans as fishing management in China is non-selective, which differs from other exploited decapod crustacean species around the world.

Assessment of Population Abundance by Hydroacoustics

AbstractThe extensive application of hydroacoustics to commercial fisheries provides a background for evaluation of its potential application to micronekton studies. Hydroacoustics has several advantages over other fishery resource assessment techniques, including high sampling power and capability for absolute population estimates, but also suffers from poor species discrimination, high complexity, and potential bias from target strength uncertainties. Application to micronekton encounters similar or even greater species identification problems and greater uncertainty associated with target characteristics, but even presently hydroacoustics offers a valuable tool for studies of patchiness and other behavioral characteristics.

Effectiveness of marine protected areas in managing the drivers of ecosystem change: a case of Mnazi Bay Marine Park, Tanzania.

Marine protected areas (MPAs) are being promoted in Tanzania to mitigate the drivers of ecosystem change such as overfishing and other anthropogenic impacts on marine resources. The effectiveness of MPAs in managing those drivers was assessed in three ecological zones, seafront, mangrove, and riverine of Mnazi Bay Marine Park, using Participatory Community Analysis techniques, questionnaire survey, checklist and fishery resource assessment methods. Eleven major drivers of ecosystem change were identified. Resource dependence had a major effect in all ecological zones of the park. The results indicated that the park's legislations/regulations, management procedures, and conservation efforts are reasonably effective in managing its resources. The positive signs accrued from conservation efforts have been realized by the communities in terms of increased catch/income, awareness and compliance. However, some natural and anthropogenic drivers continued to threaten the park's sustainability. Furthermore, implementation of resource use and benefit sharing mechanisms still remained a considerable challenge to be addressed.

Assessing size, abundance and habitat preferences of the Ocean Perch Helicolenus percoides using a AUV-borne stereo camera system

Traditional fishery resource assessment methods using trawl gear are unable to sample rocky substratum and are prone to underestimating the biomass of species having partial or strong association with rocky reefs. This study successfully used an Autonomous Underwater Vehicle (AUV) and image-yielding methods to estimate size, abundance and habitat preference of an abundant and commercially important ‘rockfish’ – the Ocean Perch (Helicolenus percoides) – in rocky habitats on the continental shelf off Tasmania, SE Australia. More than half (53%) of the Ocean Perch observed were photogrammetrically measured with known accuracy using a stereo camera system yielding length-frequency distributions. Observations of juvenile and adult H. percoides across a depth gradient showed that adults preferred rocky substrates over soft substrates, whereas juveniles preferred soft substrate over hard substrate. We found a positive relationship between rockfish abundance and increasing depth in most habitat types. These results demonstrate the utility of image-based methods for determining size composition and habitat preferences of some reef-associated species. However, there is scope to improve image-based methods using length estimation procedures that enable higher proportions of individuals to be measured (compared to the proportion achieved in this study), and by incorporating automated image annotation to decrease image analysis times, particularly when examining species/habitat relationships. The importance of analytical procedures that account for autocorrelation in non-independent image data on habitats and associated species is discussed. We conclude that rapidly maturing image-based observational methods have potential utility in complementing fishery stock assessments of some reef-associated species. Image-based methods are also well-suited to simultaneously provide additional quantitative measures of benthic habitats, invertebrate fauna and fishery environments.

Data mining and stock assessment of fisheries resources in Tonle Sap Lake, Cambodia

The potential of catch per unit effort (CPUE) analysis based on statistics of local fisheries in Tonle Sap Lake in Cambodia was evaluated. The fishery statistics system was improved through a cooperative project conducted by the Department of Fisheries and the Mekong River Commission between 1994 and 2000, especially in the seven provinces adjacent to Tonle Sap Lake. However, the fisheries statistics were not effectively utilized for sustainable stock management. After the cooperative project, fish catch data sorted by species or species group were collected at the province level in the seven provinces. Another recent project also revealed the numbers of fishing gears that operated in the seven provinces. The CPUEs of ten species in Kampong Thom Province—including Channa micropeltes and Cirrhinus spp.—could be calculated from 1994 to 2007, because these are caught solely using bamboo fence systems or barrages. CPUE analysis clarified that stocks of high-price fishes such as Ch. micropeltes, Hampala spp., and Pangasius spp. have deteriorated while those of relatively low-price fishes such as Cirrhinus spp., Cirrhinus microlepis, Cyclocheilichthys enoplos, and Channa striata have increased in recent decades.

Length-Weight Relationship of Demersal Fish from the Eastern Coast of the Mouth of the Gulf of California

The present study was performed with the purpose of describing the length-weight relationships for 64 species from 36 fish families of ecological and commercial importance, found at the soft bottom of the continental shelf on the Eastern coast of the mouth of the Gulf of California. The knowing the LWR is important because it provides information on the life history of species and may be an input to the assessment of fishery resources in the region. In this study, the demersal fish were collected during eight surveys aboard a commercial shrimp- trawling boat that operated at depths of 1 O to 60 m during the 2005/06 and 2006/07 shrimp fishing seasons. Parameter b ofthe model W = aLb varied from 1.801 to 3.916, with a mean value of 2.9511 (SD = 0.3574) and fits a normal distribution. We reported 38 new records of the LWR and 1 O of larger total length than those reported in FishBase.

An ecosystem-based fisheries assessment approach for Korean fisheries

Concern is growing over how ecosystems are being affected by fishing. A comprehensive ecosystem-based approach is required to holistically assess and manage fisheries resources and their associated habitats by considering ecological interactions of target species with predators, competitors, and prey species, interactions between fishes and their habitats, and the effects of fishing on these processes. A pragmatic ecosystem-based approach was developed for the assessment of fisheries resources in Korean waters involving three management objectives: sustainability, biodiversity, and habitat quality. A two-tier analytical method was employed. Tier 1 was designed for situations where sufficient information is available to allow for a quantitative evaluation of the status of the system, while Tier 2 was designed for situations where available information necessitated a semi-quantitative or qualitative assessment. A total of 20 Tier 1 indicators and 24 Tier 2 indicators were developed for assessment of ecosystem status. Both target and limit reference points were chosen for each indicator to assess the status of species, fisheries and ecosystems. Nested risk indices, such as objectives risk index (ORI), species risk index (SRI), fishery risk index (FRI), and ecosystem risk index (ERI), were developed to assess the ecosystem status at the management unit level. A risk assessment diagram was developed and found to be useful in quickly displaying results. A management status index (MSI) was also developed to evaluate the level of management improvement in species, fisheries, or ecosystems among different time periods or different areas. The method was demonstrated by applying it to the Tongyeong marine ranch and the Korean large purse seine fishery. It was found that this approach can be used to compare the status of species, fisheries and ecosystems spatially and temporally using an ecosystem perspective.

Age, growth, mortality and reproduction of the blackspot snapper, Lutjanus fulviflamma (Forsskål, 1775), in the southern Arabian Gulf

The population dynamics and reproductive biology of Lutjanus fulviflamma were investigated using biological and size-at-age data derived from regular monthly samples of commercial catches in the southern Arabian Gulf. Transverse sections of sagittal otoliths showed well defined structural increments consisting of alternating translucent and opaque bands which were validated as annuli. The maximum absolute age estimates were 12.8 yrs (males) and 14.3 yrs (females). The size-at-age relationships were highly asymptotic in form with the majority of growth being achieved by the second year beyond which there was little increase in size with age. There were differential growth characteristics between sexes with females increasing in size with age at a faster rate and growing to a significantly greater mean size-at-age than males. Fish were observed in spawning condition between April and July, and the mean sizes and ages at first sexual maturity were 16.7 cm L F (1.6 yrs) for males and 18.7 cm L F (1.9 yrs) for females. The relatively short lifespan, rapid initial growth, early attainment of sexual maturity and high natural mortality rate, suggest that unlike most of the larger Lutjanids, L. fulviflamma would be resilient to exploitation. Furthermore, the study demonstrates the utility of structural increments in sagittal otoliths as a foundation for age based approaches to the assessment of fisheries resources in the southern Arabian Gulf.

Decadal Changes in the Ocean Climate in Newfoundland and Labrador Waters from the 1950s to the 1990s

A review of decadal changes in the ocean climate in NAFO waters adjacent to Newfoundland and Labrador is presented based on standard station and section data and data from fishery resource assessment surveys. Both the annual trends and decadal means are examined for the decades of the 1950s to the 1990s. The analysis indicates that the 1950s and particularly the 1960s were the warmest decades during the latter half of the 20th century and the 1990s represent the third consecutive decade with below normal temperatures on the Newfoundland Shelf. The decadal mean salinity indicate that the magnitude of negative salinity anomaly on the inner Newfoundland Shelf during the 1990s was comparable to that experienced during the 'Great Salinity Anomaly' of the early 1970s. In addition, the decade of the 1990s has experienced some of the most extreme variations since measurements began during the mid-1940s. Ocean temperatures ranged from record low values during 1991 to record highs during 1999 in many areas, particularly on the Grand Bank of Newfoundland. The potential impact of the changes in ocean climate during the past several decades on marine production in Newfoundland waters is discussed.

An assessment of fishery resources of Laguna de Bay

An assessment of the major fishery resources of Laguna de Bay was conducted in 1995–1996. The study covered the socio-economics of landed fish catch and inventory of fishing gears. The socio-economic survey covered 3,055 fishermen; 87.5% were full-time workers and the rest were part-time. The total fishing effort exerted in the open waters of Laguna de Bay was 10,653,220 hours with a catch per unit effort of 0.25 kg h−1. The total fish production was 8,146 and 2,668 metric tons in 1995 and 1996, respectively. The catch mainly consisted of 13 species and was made with 20 gear types. Among the gear types, the gill net, fish corral, motorized push net, fyke net, fish pot, fish trap, and manual seine with fish shelter were considered major gear.

Demersal fish resources in the east china and yellow seas

Demersal fish resources in the East China and Yellow Seas were reviewed. A current and historical survey of the fishery was made. The distribution and migration of demersal fish were characterized, and an assessment of fishery resources was provided. The standardization of fishing efforts and resources management were also examined.

In Search of a Total Value Assessment Framework: SAFR Symposium Overview and Synthesis

The Social Assessment of Fisheries Resources (SAFR) Symposium explored potentials for more fully using the problem-solving abilities of social sciences in fishery management. The SAFR papers examine the theory, methods, and applications of economics, sociology, anthropology, political science, and philosophy in relation to the kinds of evaluations faced by fishery managers, particularly in North Americaˈs Great Lakes region. In this symposium overview, we consider whether a “total value framework” could be developed to assess all pros and cons of changes in fishery resources. We reject the notion of a perfect, uniform, quantitative total value assessment method, recognizing that existing assessment practices underrepresent some value elements and overrepresent others. Total value concepts must consider both basic human values (“held” values) and monetary or equivalent values, such as those in benefit–cost analysis (“assigned” values). Out total value framework illustrates the difficulty of reconciling these disparate types of human values in ways that lend practical guidance for evaluating fishery management choices. We survey the SAFR papers within this total value framework, considering the potential contributions and shortcomings of each discipline in evaluating human value changes.

Investigations into the accuracy and precision of hydroacoustic techniques for fishery resource assessment

Hydroacoustic techniques are becoming widely used in fishery resource assessment. There are many sources of variability and uncertainty in these techniques, and their accuracy and precision has been questioned. Studies at the University of Washington have evaluated the performance of hydroacoustic techniques in a variety of applications where substantial ground truth data were available. These studies have documented the magnitude of several variance components and shown that many of the larger sources of variability are biological rather than physical. [Work supported by Sea Grant.]