Population Characteristics of Gulf Menhaden, Brevoortia patronus

The status of the gulf menhaden, Brevoortia patronus, fishery was assessed with purseseine landing data from 1946 to 1992 and port sampling data from 1964 to 1992. These data were analyzed to determine growth rates, biological reference points for fishing mortality from yield per recruit and maximum spawning potential analyses, spawner-recruit relationships, and maximum sustainable yield (MSY). Virtual population approaches were used to obtain point estimates of stock size, recruits to age I, spawning stock size, and fishing mortality rates. Exploitation rates ranged between 14% and 45% for age-1 fish, between 30% and 72% for age-2 fish, and between 36% and 71% for age-3 fish. Biological reference points from yield per recruit (FO. I: 0.7-0.9 yr-1) and maximum spawning potential (F20: 1.62.9 yr-l and F30: 1.0-2.1 yr-1) were obtained for comparison with recent estimates of F (0.4-0.8 yr-l). Parameters from Ricker-type spawner-recruit relations were estimated, although considerable unexplained variability remained. Estimates of long-term MSY from fits of the generalized production model ranged between 664,000 metric tons (t) and 897,000 t. Declines in landings since 1988 have raised concerns about the status of the gulf menhaden stock. However, gulf menhaden are short lived and highly fecund. Thus, variation in recruitment to age 1 largely mediated by environmental conditions influences fishing success over the next two years (as age-1 and age-2 fish). Comparisons of recent estimates of fishing mortality to biological reference points do not suggest overfishing. (PDF file contains 26 pages.)

Distribution, Abundance, and Biological Characteristics of Groundfish off the Coast of Washington, Oregon, and California, 1977-1986

We compare results of bottom trawl surveys off Washington, Oregon, and California in 1977, 1980, 1983, and 1986 to discern trends in population abundance, distribution, and biology. Catch per unit of effort, area-swept biomass estimates, and age and length compositions for 12 commercially important west coast groundfishes are presented to illustrate trends over the lO-year period. We discuss the precision, accuracy, and statistical significance of observed trends in abundance estimates. The influence of water temperature on the distribution of groundfishes is also briefly examined. Abundance estimates of canary rockfish, Sebastes pinniger, and yellowtail rockfish, S. Jlavidus, declined during the study period; greater declines were observed in Pacific ocean perch, S. alutus, lingcod, Ophiodon elongatus, and arrowtooth flounder, Atheresthes stomias. Biomass estimates of Pacific hake, Merluccius productus, and English, rex, and Dover soles (Pleuronectes vetulus, Errex zachirus, and Microstomus pacificus) increased, while bocaccio, S. paucispinis, and chilipepper, S. goodei, were stable. Sablefish, Anoplopoma fimbria, biomass estimates increased markedly from 1977 to 1980 and declined moderately thereafter. Precision was lowest for rockfishes, lingcod, and sablefish; it was highest for flatfishes because they were uniformly distributed. The accuracy of survey estimates could be gauged only for yellowtail and canary rockfish and sablefish. All fishery-based analyses produced much larger estimates of abundance than bottom trawl surveys-indicative of the true catchability of survey trawls. Population trends from all analyses compared well except in canary rockfish, the species that presents the greatest challenge to obtaining reasonable precision and one that casts doubts on the usefulness of bottom trawl surveys for estimating its abundance. (PDF file contains 78 pages.)

An assessment of co-management potentials in the Lake Victoria fisheries of Kenya

Co-management is a system or a process in which responsibility and authority for the management of common resources is shared between the state, local users of the resources as well as other stakeholders, and where they have the legal authority to administer the resource jointly. Co-management has received increasing attention in recent years as a potential strategy for managing fisheries. This paper presents and discusses results of a survey undertaken in the Kenyan part of Lake Victoria to assess the conditions - behaviour, attitude and characteristics of resource users, as well as community institutions - that can support co-management. It analyses the results of this survey with respect to a series of parameters, identified by Pinkerton (1989), as necessary preconditions for the successful inclusion of communities involvement in resource management. The survey was implemented through a two-stage stratified random sampling technique based on district and beach size strata. A total of 405 fishers, drawn from 25 fish landing beaches, were interviewed using a structured questionnaire. The paper concludes that while Kenya's lake Victoria fishery would appear to qualify for a number of these preconditions, it would appear that it fails to qualify in others. Preconditions in this latter category include the definition of boundaries in fishing grounds, community members' rights to the resource, delegation and legislation of local responsibility and authority. Additional work is required to further elaborate and understand these shortcomings

Demographic characteristics of exploited tropical lutjanids: a comparative analysis

Demographic parameters from seven exploited coral reef lutjanid species were compared as a case study of the implications of intrafamily variation in life histories for multispecies harvest management. Modal lengths varied by 4 cm among four species (Lutjanus fulviflamma, L. vitta, L. carponotatus, L. adetii), which were at least 6 cm smaller than the modal lengths of the largest species (L. gibbus, Symphorus nematophorus, Aprion virescens). Modal ages, indicating ages of full selection to fishing gear, were 10 years or less for all species, but maximum ages ranged from 12 (L. gibbus) to 36 years (S. nematophorus). Each species had a unique growth pattern, with differences in length-at-age and mean asymptotic fork length (L∞), but smaller species generally grew fast during the first 1–2 years of life and larger species grew more slowly over a longer period. Total mortality rates varied among species; L. gibbus had the highest mortality and L. fulviflamma, the lowest mortality. The variability in life history strategies of these tropical lutjanids makes generalizations about lutjanid life histories difficult, but the fact that all seven had characteristics that would make them particularly vulnerable to fishing indicates that harvest of tropical lutjanids should be managed with caution.

Evaluation of the carcass and commercial characteristics of carps

The role of carcass evaluation techniques in aquaculture research programs, especially in genetics, breeding, production management, feeding and nutrition, cannot be overemphasized. Knowledge of production efficiencies and growth potentials in relation to desired carcass attributes has provided an impetus to improvements in genetic selection techniques and management of aquatic food animals. Accurate, standard and uniform methods of carcass evaluation are critically important. A standard format developed for collection of data on carps is presented in this paper.

Biological Characteristics and Fishery Assessment of Alaska Plaice, Pleuronectes quadrituberculatus, in the Eastern Bering Sea

Alaska plaice, Pleuronectes quadrituberculatus, is one of the major flatfishes in the eastern Bering Sea ecosystem and is most highly concentrated in the shallow continental shelf of the eastern Bering Sea. Annual commercial catches have ranged from less than 1,000 metric tons (t) in 1963 to 62,000 t in 1988. Alaska plaice is a relatively large flatfish averaging about 32 cm in length and 390 g in weight in commercial catches. They are distributed from nearshore waters to a depth of about 100 m in the eastern Bering Sea during summer, but move to deeper continental shelf waters in winter to escape sea ice and cold water temperatures. Being a long-lived species (>30 years), they have a relatively low natural mortality rate estimated at 0.20. Maturing at about age 7, Alaska plaice spawn from April through June on hard sandy substrates of the shelf region, primarily around the 100 m isobath. Prey items primarily include polychaetes and other marine worms. In comparison with other flatfish, Alaska plaice and rock sole, Pleuronectes bilineatus, have similar diets but different habitat preferences with separate areas of peak population density which may minimize interspecific competition. Yellowfin sole, Pleuronectes asper, while sharing similar habitat, differs from these two species because of the variety of prey items in its diet. Competition for food resources among the three species appears to be low. The resource has experienced light exploitation since 1963 and is currently in good condition. Based on the results of demersal trawl surveys and age-structured analyses, the exploitable biomass increased from 1971 through the mid-1980’s before decreasing to the 1997 level of 500,000 t. The recommended 1998 harvest level, Allowable Biological Catch, was calculated from the Baranov catch equation based on the FMSY harvest level and the projected 1997 biomass, resulting in a commercial harvest of 69,000 t, or about 16% of the estimated exploitable biomass.

Travel Characteristics of Marine Anglers Using Oil and Gas Platforms in the Central Gulf of Mexico

This study was designed to evaluate the travel characteristics of avid marine anglers off Louisiana in the Central Gulf of Mexico. It focuses on the complex marine travel patterns involving the extensive assemblage of oil and gas structures. In an intercept approach, marine recreationalf isherman were asked to identify near and offshore travel patterns on the day of the interview. Information was also solicited regarding how respondents selected and located fishing destinations as well as what method of fishing was undertaken that day. Petroleum platforms were a principal fishing destination, and platform anglers traveled an average distance of 75.5 km (40.7 n.mi.) to and from offshore fishing locations. In fishing an average of 6.5 platforms per trip, these anglers traveled about 21.3 km (11.5 n.mi.) between the first and last platform visited. Mean total distances for platform anglers were 96 km (51.8 n.mi). Travel distances for bay, nearshore, and bluewater anglers were also obtained.

Management strategies for exploitation of Uganda fisheries resources

Fisheries legislation in Uganda has not been feasibly applicable to all Uganda water bodies and species therein. Failure to make appropriate legislation to regulate fishing gears and methods has led to the decline or near collapse of some fisheries. Most fisheries have been damaged by destructive fishing gears and methods. Selectivity characteristics of several gears and fishing methods were therefore examined for different commercially important fish species in major and minor lakes and recommendations made on suitable types of gears, gear sizes and fishing methods for exploitation of the fisheries resource.

Study on regional differences in soil-water characteristics and their relevance to aquaculture productivity and fish disease

A total of 45 ponds used for fish polyculture were investigated in three zones of Bangladesh to identify the differences among the zones in respect to aqua-ecology, culture practices, fish productivity and health management. Four hundred and fifty fish from three zones were clinically examined by naked eye and histopathology. Out of total number of fish examined, 45 fish from Dhaka zones were examined for parasites and bacteria in addition to histopathology. Faded and haemorrhagic gill, skin, fin, scale loss and lesions were observed during fish examination. Aeromonas spp. Pseudomonas spp. and Streptococcus spp. were isolated respectively from 56%, 46% and 39% affected fish. Among the five water quality parameters analyzed, the highest average hardness and alkalinity respectively were recorded in Rajshahi (156 ppm and 142 ppm) followed by Dhaka (146 ppm and 132 ppm) and Chittagong (81 ppm and 90 ppm). The highest average pH was recorded in Mymensingh (7.52) followed by Rajshahi (7.13) and Chittagong (7.05). Water holding capacity of soil in Rajshahi zone was poor compared to other zones and farmers were found to be reluctant to fish farming.

The study of biological characteristics and determination of population dynamic parameters of sawtooth barracuda (Sphyraena putnamae) in the Persian Gulf (Hormozgun Province waters)

The biological characteristics and population dynamisms of Sphyraena putnamae, were studied in the northern Persian Gulf and Oman Sea restricted to Hormuzgan province waters within 13 months period, from November 2006 up to November 2007. Biometrical and anatomical measurements were carried out, and biological surveys were conducted on 486 specimens. On the other hand, the growth and mortality parameters were estimated by using 3096 samples. These samples were collected from 3 landings, namely Bandar Abbas, Bandar Lengeh and Bandar Jask. The measurements of the minimum and maximum Fork lengths and weights were 11.7 to 8.03 cm and 135.0 to 4140.0 g, respectively. The results indicated that this species, having the Relative Length of Gut, RLG=0.34±0.002, is strongly carnivorous (often fish-eater), proven by the fact that more than 98% of its stomach contents were fish pieces. Examining the changes in the index of stomach emptiness by the percentage of CV = 0.47% indicates that this fish is Moderate feeder. The level of feeding increased in March, before spawning and decreased in June and September, simultaneously with the spawning season. There are 2 peaks of reproduction or spawning seasons during the months of April-May and September, of which the prior is assumed as the main spawning. The sex ratio (M:F) was calculated 0.5:1.0(X2 =2.11), which did not show a significant difference with expected level of 1:1 (P>0.05). The average absolute and relative reproduction rates of Sphyraena putnamae is respectively as follows: 1866827.1±255448.9 and 1097.7±94.3. The highest and the lowest diameter of matured egg are from 200 to 750 μ, and its average diameter is 402.10 ± 0.190 μ. A parameter for Saw-tooth barracuda length measurement, Lm50, based on the Fork-length, was calculated as 54.01 cm. In other words, as far as the fisheries management is concerned, the fish whose lengths are less than 54.01 cm should not be caught. The calculated level of (R2) (correlations of total length & weight), indicated strong correlations between length and weight of this fish, and the obtained formula included W =0.007100 FL 2.9295 and reinforced this assumption. The “K” Index for this fish in 3 above mentioned landings (Jask, Bandar-Abbas and Bandar-Length) were 1.24, 0.37 and 0.46 per year, respectively and the FL index for the same landings were estimated as 129, 110 and 134 cm, respectively. The growth coefficient (MONRO) for the above mentioned regions were calculated as 3.601, 3.647 and 3.917, respectively; and in the surveyed regions there were no significant differences in populations. The Total mortality coefficient (Z) was calculated 0.76, 1.12 and 1.07 per year, the Natural mortality coefficient was 0.46, 0.63 and 0.70, and the Fishing mortality coefficient (rate) (F) was found to be 0.30, 0.49 and 0.37 per year. The value of the exploitation rate (E) is equal to 0.39 per year, indicating that this species is an under-exploited resource, and there is no excessive fishing pressure on the fish supply of this species in the afore-said regions. The highest level of exploitation was found for ‘Bandar Abbas’ fishing region and the lowest level of exploitation is in ‘Bandar Lengeh’ waters.

Population dynamics and management of yellowfin tuna (Thunnus albacares) of the Oman Sea

The Yellowfin tuna was caught more than all other species in the southern waters of Iran (24000 tons in 1998). In order to come up with the responsible fishing pattern, there was a need to identify some of the biological characteristics and population dynamic parameters. This thesis was the first which covered the whole Yellowfin tuna distribution in the Oman Sea, included the fishing grounds of Berris, Ramin, Chabahar, Pozm and Jask. The data during 1998-99 from different fishing grounds were polled. Based on the exponential relationship between length and weight in the size range 38-173 Cm, the relationship (W=aL^ b) was calculated as W=0.000012L ^ 3.0831). The mean fork length,head length,girth and weight were calculated respectively 84.15 Cm, 23 Cm, 53 Cm, and 11828 g. Length infinity was estimated 189 Cm with growth parameters of 0.42 per year. Growth performance index was 4.18 which was in agreement with the findngs of the other studies in the Indian and Pacific Oceans. The mortality parameters and exploitation rate were estimated as below: Z = 1.75-1.85 M=0.6 F=1.25 E=0.68 Occurence of empty stomach was high (60%) in the speciemens obtained from the Oman Sea. Purpleback flying squid (Sthenoteuthis oualaniensis) was the most dominant prey species observed in the study (57% in females and 60% in males), occurrence of teleost fishes were found to be the second (38% in males and 42% in females). Crabs also were identified in the specimens(1-2%). The study on sex ratio indicated that males were predominant at all sizes above 120 Cm fork length. 50.82% of specimens were males and 49.18% females. The monthly gonadosomatic index was deriven higher values during January to June which could be indicated as spawning period.

Report of the Workshop on Marine Protected Area Management in Myanmar, Myeik, Myanmar, 2-3 October, 2014

The objectives of the workshop included: an overview of the biophysical characteristics of the Myeik Archipelago; strengthen understanding of Marine Protected Areas (MPAs) management to mitigate resource use conflicts; share lessons and experiences of MPA management from the Asia-Pacific region; and to identify a road map for developing MPA management in the Myeik Archipelago.

Priorities for research and management on Lake Victoria

Under the worrisomely changing situation in fish species diversity, water environment characteristics, socio-economic dimensions and other ecosystems variables in Lake Victoria, there is an urgent need to put in place effective research and management packages aimed at safe guarding the sustainability of the vast resources of the lake. Priority in have been out-lined to develop strategies which would promote biological productivity and diversity, and socio-economic returns. But given the size of the lake (69,000 km2) and the complexity of dynamic forces which are driving the changes, coordinated approach for research and management among the riparian states and the international scientific community will be required. The task is not only extensive but urgent as well.

The effect of ecological changes in Lake Victoria on the present trophic characteristics of Oreochromis niloticus in relation to the species' role as a stabilizing factor of biomanipulation

The Lake Victoria ecosystem has experienced such a profound ecological change that Oreochromis niloticus - an introduced species, is the only important cichlid (out of the original 250 + spp) left in the lake. It is the basis of an important commercial fishery which is intensely exploited by sophisticated methods. An investigation of its feeding habits at present indicates that the species could also playa major role in the energy flux of the lake. Fisheries management in Lake Victoria will thus require multi-disciplinary studies which reflect a total ecosystem approach.

Changes in catches and biological characteristics of Nile tilapia (Oreochromis niloticus Linnaeus) in Lake Wamala (Uganda) under changing climatic conditions

There have been changes in catches and biological characteristics of the Nile Tilapia, Oreochromis niloticus (Linnaeus) in Lake Wamala (Uganda) since its introduction and establishment, but the factors which have contributed to these changes are not adequately understood. This study examined changes in catches and biological characteristics of Nile tilapia in relation to changes in temperature, rainfall and lake depth to provide an understanding of the role of changing climatic conditions. There was an increase in minimum, maximum and average temperature since 1980, but only minimum (0.021ºCyr-1) and average (0.018ºCyr-1) showed a significant trend (p < 0.05). Rainfall increased by 8.25 mmyr-1 since 1950 and accounted for 79.5% of the water input into the lake while evaporation accounted for 86.2% of the water loss from the lake. The lake depth was above 4 m during the years rainfall was above normal average of 1180 mm, except during the period 2011-2014. The contribution of Nile tilapia to total catch and CPUE changed with rainfall and lake depth up to 2000, after which they decreased despite increase in rainfall. There was a strong positive correlation between lake depth and average total length of Nile tilapia (r = 0.991, p < 0.001) and length at 50% maturity (r = 0.726, p < 0.001). The length-weight allometry between high and low lake depths was significantly different [t (6) = 3.225, p < 0.05], with Nile tilapia being heavier (for a given length) at high lake depth than at low lake depth. Fecundity of Nile tilapia was higher and egg diameter lower than what is reported in literature. Nile tilapia shifted from algal dominated diet during the wet season to include more insects during the dry season. The study showed that the catches and biological characteristics of Nile tilapia change with climate and hydrological factors and these need to be considered in management of the fisheries of Lake Wamala.