Assessment of Atlantic Red Drum for 1999: Northern and southern regions

An assessment of the status of the Atlantic stock of red drum is conducted using recreational and commercial data from 1986 through 1998. This assessment updates data and analyses from the 1989, 1991, 1992 and 1995 stock assessments on Atlantic coast red drum (Vaughan and Helser, 1990; Vaughan 1992; 1993; 1996). Since 1981, coastwide recreational catches ranged between 762,300 pounds in 1980 and 2,623,900 pounds in 1984, while commercial landings ranged between 60,900 pounds in 1997 and 422,500 pounds in 1984. In weight of fish caught, Atlantic red drum constitute predominantly a recreational fishery (ranging between 85 and 95% during the 1990s). Commercially, red drum continue to be harvested as part of mixed species fisheries. Using available length-frequency distributions and age-length keys, recreational and commercial catches are converted to catch in numbers at age. Separable and tuned virtual population analyses are conducted on the catch in numbers at age to obtain estimates of fishing mortality rates and population size (including recruitment to age 1). In tum, these estimates of fishing mortality rates combined with estimates of growth (length and weight), sex ratios, sexual maturity and fecundity are used to estimate yield per recruit, escapement to age 4, and static (or equilibrium) spawning potential ratio (static SPR, based on both female biomass and egg production). Three virtual analysis approaches (separable, spreadsheet, and FADAPT) were applied to catch matrices for two time periods (early: 1986-1991, and late: 1992-1998) and two regions (Northern: North Carolina and north, and Southern: South Carolina through east coast of Florida). Additional catch matrices were developed based on different treatments for the catch-and-release recreationally-caught red drum (B2-type). These approaches included assuming 0% mortality (BASEO) versus 10% mortality for B2 fish. For the 10% mortality on B2 fish, sizes were assumed the same as caught fish (BASEl), or positive difference in size distribution between the early period and the later period (DELTA), or intermediate (PROP). Hence, a total of 8 catch matrices were developed (2 regions, and 4 B2 assumptions for 1986-1998) to which the three VPA approaches were applied. The question of when offshore emigration or reduced availability begins (during or after age 3) continues to be a source of bias that tends to result in overestimates of fishing mortality. Additionally, the continued assumption (Vaughan and Helser, 1990; Vaughan 1992; 1993; 1996) of no fishing mortality on adults (ages 6 and older), causes a bias that results in underestimates of fishing mortality for adult ages (0 versus some positive value). Because of emigration and the effect of the slot limit for the later period, a range in relative exploitations of age 3 to age 2 red drum was considered. Tuning indices were developed from the MRFSS, and state indices for use in the spreadsheet and FADAPT VPAs. The SAFMC Red Drum Assessment Group (Appendix A) favored the FADAPT approach with catch matrix based on DELTA and a selectivity for age 3 relative to age 2 of 0.70 for the northern region and 0.87 for the southern region. In the northern region, estimates of static SPR increased from about 1.3% for the period 1987-1991 to approximately 18% (15% and 20%) for the period 1992-1998. For the southern region, estimates of static SPR increased from about 0.5% for the period 1988-1991 to approximately 15% for the period 1992-1998. Population models used in this assessment (specifically yield per recruit and static spawning potential ratio) are based on equilibrium assumptions: because no direct estimates are available as to the current status of the adult stock, model results imply potential longer term, equilibrium effects. Because current status of the adult stock is unknown, a specific rebuilding schedule cannot be determined. However, the duration of a rebuilding schedule should reflect, in part, a measure of the generation time of the fish species under consideration. For a long-lived, but relatively early spawning, species as red drum, mean generation time would be on the order of 15 to 20 years based on age-specific egg production. Maximum age is 50 to 60 years for the northern region, and about 40 years for the southern region. The ASMFC Red Drum Board's first phase recovery goal of increasing %SPR to at least 10% appears to have been met. (PDF contains 79 pages)

An evaluation of Northern Florida Bay as a nursery area for red drum, Sciaenops ocellatus, and other juvenile and small resident fishes.

Red drum is one ofthe most popular species sought by anglers in Florida Bay, yet juveniles are rarely encountered. We evaluated Florida Bay as a nursery area for red drum by sampling for recently-settled late larvae in basin areas within the bay with an epi-benthic sled at six stations in November 2000, and at seven stations during December 2000 through February 2001. In November 2000 we surveyed potential sampling sites in quiet backwaters adjacent to mangroves for juvenile red drum. A total of 202 sites were sampled mainly in northern Florida Bay and adjacent waters with a cast net. We collected only one recently-settled red drum larvae and no juveniles. Obviously the sites that we sampled in Florida Bay and adjacent waters are not nursery habitat for this valuable species. Sled collections were dominated by bay anchovy, Anchoa mitchilli, but densities were biased by one collection. Five small resident species were among the dominant species: rainwater killifish, Lucania parva; dusky pipefish, Syngnathus floridae; dwarf seahorse, Hippocampus zosterae; and clown goby, Microgobius gulosus. Three species that spawn outside Florida Bay in the GulfofMexico were common: pinfish, Lagodon rhomboides; pigfish, Orthopristis chrysoptera; and silver perch, Bairdiella chrysoura. Twenty-seven species were collected with the cast net. Hardhead silversides (Atherinomorus stipes), bay anchovy, tidewater mojarra (Eucinostomus harengulus), silver jenny (Eucinostomus gula), and goldspotted killifish (Floridichthys carpio) were the most common in cast net collections. Although only one red drum was collected, we were able to: (1) identify mesohaline waters from our cast net sites to test our preliminary assessment that mesohaline habitat might be limited in Florida Bay, (2) document the distribution and abundance of fishes collected by cast net that should enhance our understanding of ichthyofauna in the Northern Subdivision ofFlorida Bay and adjacent waters, and (3) from epibenthic sled collections, describe the habitats, abundance and distribution of recently settled larvae/small juveniles/small resident fishes during late fall and winter. This information should be useful to managers and future research. (PDF contains 34 pages)

Bag and size limit analyses for red drum in Northern and Southern Regions of the U.S. Atlantic

Assessments of the Atlantic red drum for the northern (North Carolina and north) and southern (South Carolina through east coast of Florida) regions along the U. S. Atlantic coast were recently completed. The joint Red Drum Technical Committee (SAFMC/ASMFC) selected the most appropriate catch matrix (incorporating an assumption on size of recreationally-released fish), selectivity of age 3 relative to age 2, and virtual population analysis (FADAPT). Given gear- and age-specific estimates of fishing mortality (F) for the 1992-1998 period, analyses were made of potential gains in escapement through age 4 and static spawning potential ratio (SPR) from further reductions in fishing mortality due to changes in slot and bag limits. Savings from bag limits were calculated given a particular slot size for the recreational fishery, with no savings for the commercial fisheries in the northern region due to their being managed primarily through a quota. Relative changes in catch-at-age estimates were used to adjust age-specific F and hence calculated escapement through age 4 and static SPR. Adjustment was made with the recreational savings to account for release mortality (10%, as in the stock assessment). Alternate runs for the northern region commercial fishery considered 25% release mortality for lengths outside the slot (instead of 0% for the base run), and 0% vs. 10% gain or loss across legal sizes in F. These results are summarized for ranges of bag limits with increasing minimum size limit (for fixed maximum size), and with decreasing maximum size limit (for fixed minimum size limit). For the southern region, a bag limit of one-fish per angler trip would be required to attain the stated target of 40% static SPR if the current slot limit were not changed. However, for the northern region, a bag limit of one-fish per angler trip appears to be insufficient to attain the stated target of 40% static SPR while maintaining the current slot limit. (PDF contains 41 pages)

Hydroacoustic evaluation of spawning red hind (Epinephelus guttatus) aggregations along the coast of Puerto Rico in 2002 and 2003

Red hind (Epinephelus guttatus) have been overfished in the Caribbean and were included with seven other regional grouper species deemed vulnerable to risk of extinction. The Puerto Rico Department of Natural and Environmental Resources desired to map spawning red hind aggregations within commonwealth waters as part of their resource management program for the species. Mobile hydroacoustic surveys were conducted over 3-day periods in 2002 and 2003, indexed to the full moon phase in February or March when red hind were known to aggregate. Four vessels concurrently sampled the southwest, south, and southeast coasts of Puerto Rico in 2002. In 2003, three vessels conducted complementary surveys of the northwest, north, and northeast coasts of the island, completing a circuit of the coastal shelf-spawning habitat. These surveys indicated that red hind spawning aggregations were prevalent along the south and west coasts, and sparse along the north coast during the survey periods. Highest spawning red hind concentrations were observed in three areas offshore of the west coast of Puerto Rico, around Mona and Desecheo islands (20,443 and 10,559 fish/km2, respectively) and in the Bajo de Cico seasonal closed area (4,544 fish/km2). Following both 2002 and 2003 surveys, a series of controlled acoustic measurements of known local fish species in net pens were conducted to assess the mean target strength (acoustic backscatter) of each group. Ten species of fish were measured, including red hind (E. guttatus), coney (E. fulvus), white grunt (Haemulon plumieri), pluma (Calamus pennatula), blue tang (Acanthurus coeruleus), squirrel fish (Holocentrus spp.), black durgeon (Melichtyhs niger), ocean file fish (Canthidermis sufflamen), ocean surgeon fish (Acanthurus bahianus), and butter grouper (Mycteroperca spp.). In general, the mean target strength results from the caged fish experiments were in agreement with published target strength length relationships, with the exception of white grunt and pluma.

Producing tilapia in small cage in West Africa

This document is part of a series of 5 technical manuals produced by the Challenge Program Project CP34 “Improved fisheries productivity and management in tropical reservoirs”. The Water Research Institute (WRI) in Akosombo, Ghana, is working to bring cage aquaculture technology to smallholder farmers. The stocking, feeding and cage-construction technology piloted by WRI is now being widely adopted in the Lower Volta basin in Ghana. The results of WRI research over the period 2005-2009 are presented here as a guide to potential investors. (PDF contains 19 pages)

Genetic improvement and utilisation of indigenous tilapia in southern Africa: final technical report, December 1st 1998 to June 31st, 2002

Mozambique tilapia (Oreochromis mossambicus) is an indigenous tilapia species in southern Africa, until now the majority of genetic research has been carried out on Asian species of tilapia but this project aims to look at this African species. Those most suited to further development in aquaculture in southern Africa have now been identified. The genetic characterisation of strains has been completed. This information has aided the choice of strains for use in small scale aquaculture and for genetically male tilapia (GMT) production. They will form the basis of future strategies for further genetic improvement, and management of genetic diversity of Mozambique tilapia. The information will also contribute towards responsible management and development of genetic resources, particularly with regard to indigenous species of tilapia. Good progress has been made with the adaptation and implementation of producing the supermale fish required to produce all male offspring, resulting in faster growing populations of tilapia. The presence of the project and its associated activity has been a catalyst for a surge in interest in tilapia culture throughout southern Africa. [PDF contains 183 pages]

Entwicklung einer einfachen und schnellen Analysenmethode für Kohlenmonoxid in Fisch und Durchführung orientierender Untersuchungen

Treatment with gases containing CO, misleadingly called “tasteless smoke” or “clear smoke”, prior to freezing of fish like tuna, tilapia and swordfish (to name only a few of these species that are characterised by an intensive coloration of flesh) stabilise the fresh red colour of muscle also after thawing and suggest consumers non-existing freshness. In the European Union, carbon monoxide is excluded from being a permitted additive and therefore this handling is not allowed. Notwithstanding of the clear legal position, producers and traders are trying to establish CO treated fish on the market. In the case of taking legal measures the food control laboratories have to provide evidence that fish has been treated by CO and therefore a respective method is necessary. The method of determination of carbon monoxide in fish flesh presently applied requires considerable material and mechanistic effort to detect CO by GC after catalytic transformation into methane. The aim of our work was a direct detection of CO using suitable sensor technology. Mechanistic requirements and results of preliminary investigations to detect carbon monoxide in fish flesh will be described.

The growth of Sarotherodon (Tilapia) niloticus L. in Opa Reservoir, University of Ife, Ile-Ife, Nigeria

The growth of Sarotherodon (Tilapia) niloticus in Opa reservoir, University of Ife was determined from the fish scales. Compared with the growth in other similar water bodies the growth was comparatively faster in this newly-impounded reservoir

Intestinal absorption by Sarotherodon galilaeus (syn Tilapia galilaea ) of Lake Kainji, Nigeria

Carbohydrates, protein, lipid and crude fibre were found to reduce in amount from the anterior to posterior regions along the gut of Sarotherodon galilaeus collected from Lake Kainji. Different regions of the gut exhibited different absorptive powers and all the compounds were differently absorbed in amount. Different sizes of fish showed different absorptive capacity

Quality changes in canned tilapia stored at ambient and accelerated temperatures

Changes in the quality of canned tilapia packed in oil and tomato sauce at ambient and accelerated temperatures were examined by microbiological and sensory evaluation. Canned tilapia were found to be microbiologically stable and organoleptically acceptable after six months storage period. Total viable count (TVC) were generally low (2.5 x 10 super(2)). Thermophilic organisms (Clostridium) were absent in all samples. The yield of edible part of tilapia was 72% after dressing. Pre-cooking of tilapia resulted in a loss of 21.5% of its dressed weight. Comparison of canned tilapia with available canned fishes (geisha and bonga) showed similar trends in the taste, proximate composition, microbiological stability and sensory scores.The possibility for investment in tilapia cannary was also investigated. It was found that production of canned tilapia will be economically viable if a ten hectare tilapia farm is used as a source of raw materials.

Duckweed (Lemna paucicostata Heglem ex Engle) in the diet of tilapia (Sarotherodon galilaeus)

The growth of Sarotherodon galilaeus fingerlings fed with test diet of 33% crude protein and containing 10% duckweed was compared with standard KLRI/40/6 feed of 40% crude protein. From an initial mean weight of 1.18gm and 1.17gm, the fingerlings in the test diet and control respectively grew to a final mean weight of 2.17gm and 1.98gm after seven weeks. With mean growth rate of 2.02% and 1.65% of their body weight per day respectively for the test diet and the control, it was obvious that the test diet was better and had a higher food conversion than the control. The duckweed must have therefore, supplied some essential amino acids to the test diet thereby making it a higher quality feed

The effects of supplemental feeds containing different protein: Energy ratios on the growth and survival of Tilapia nilotica (Oreochromis niloticus) in brackishwater ponds

A research was conducted in thirty approximately 100 sq.m earthern ponds of the Brackishwater Aquaculture Centre (BAC), College of Fisheries, University of the Philippines, Leganes Iloilo from November 7, 1982 to March 7, 1983 to evaluate the effects of nine supplemental feeds containing different protein: energy ratios on the growth and survival of Tilapia nilotica in brackishwater ponds. Nine supplemental feeds formulated were with protein levels of 20%, 25%, and 30% each at three energy levels of 3,000 kcals; 3,500 kcals; and 4,000 kcals. There was a control treatment with no feeding so that mean weight gain growth rate, feed conversion rate, and survival were determined. Fish fingerlings were acclimated from 0-29 ppt. salinity before the experiment and 20% of fish in each treatment were sampled after every 30 days. Growth rates were significantly different and increased with increasing energy level at the 30% protein feeds but decreased at high energy levels in the 20% and 25% protein feeds. Feed conversion was significantly different due to interaction between protein and energy levels in the feeds, and was better at the 30:3,500 kcals feeds having a feed conversion of 1.55 g. Survival was not significantly different

Pyridoxine and survival of tilapia (Sarotherodon mossambicus Peters)

Pyridoxine requirements of tilapia (Sarotherodon mossambicus Peters) were studied in two separate experiments using casein-based diets. In Experiment 1, fish on pyridoxine supplemented diet (14.0mg/100g diet) showed no adverse symptoms and remained healthy while fish on a pyridoxine-free diet showed abnormal behaviour with high mortality. Graded dietary pyridoxine (0.13 to 3.52mg/100g diet) was used in Experiment 2. Lower dietary supplementations of pyridoxine resulted in reduced weight increase, high mortality, high ratio of serum glutamate-oxal-acetate transaminase glutamate-pyruvate transaminase, and reduced blood sugar. The results suggest the dietary requirement of pyridoxine may be between 0.5g and 1.17mg/100g diet; higher supplementations did not appear to confer any further benefits

Small scale commercial production of tilapia fingerlings in floating bamboo net-hapas

The inadequate supply of tilapia seed is considered as one of the major present constraints to the development of the culture industry in Nigeria. The floating bamboo net-hapa hatchery/nursery system was observed to be very efficient in the mass production of tilapia (Oreochromis niloticus) fry and fingerlings at Kainji Lake Research Institute. This system was therefore, recommended for small-scale (artisanal) commercial operators consisting of fishermen families in order to increase their productivity and hasten development of rural communities. The economic analysis of this system showed that loan obtained for the recommended scale of operation can be amortized within 2 years of the project. It was emphasized that the operational and managerial skills of the fish farm operators account largely to the production cost and profitability of the enterprise