Bioconversion efficiency and growth in the white shrimp Penaeus indicus (Milne Edwards), fed with decomposed mangrove leaves

Food conversion efficiency and growth in the white shrimp Penaeus indicus fed with decomposed mangrove leaves of Avicennia marina and A. officinalis were monitored under laboratory conditions. It was observed that test animals fed with the decomposed leaves of A. marina had higher assimilation efficiency (87.96%), gross growth efficiency (10.82%), net growth efficiency (12.3%) and relative growth rate (0.0603 g/day) than those fed with A. officinalis. The relatively higher growth registered in the animals fed with decomposed leaves of A. marina was attributed to its high calorific and protein content.

Review of the California Trawl Fishery for Pacific Ocean Shrimp, Pandalus jordani, from 1992 to 2007

The commercial bottom trawl fishery for Pacific ocean shrimp, Pandalus jordani, or pink shrimp, operates mostly off the west coast of the contiguous United States. The California portion of the fishery has not been thoroughly documented or reviewed since the 1991 fishing season, despite its fluctuating more during the last 16 years (1992–2007) than at any other period in its 56-year history. We used fishery-dependent data, California Department of Fish and Game commercial landing receipts and logbook data, to analyze trends and review the California pink shrimp trawl fishery from 1992 to 2007. In particular, we focus on the most recent years of the fishery (2001–07) to highlight the gear developments and key management measures implemented in the fishery. The fishery is primarily driven by market conditions and is highly regulated by both state and Federal management agencies. Several key regulatory measures implemented during this decade have had significant effects on the fishery. For example, the requirement of a Bycatch Reduction Device on trawl nets targeting pink shrimp was approved in 2001 and has greatly reduced levels of finfish bycatch. Fishery production has declined, particularly in recent years, and may be attributed to decreased market prices, followed by reduced fishermen participation; both of which are related to changes in the processing sector and demand for the product.

An Accounting of the Sources of Steller Sea Lion, Eumetopias jubatus, Mortality

During 1991–2000, the west-are additional mortalities that fueled the ern stock of Steller sea lions, Eumetopias decline. We tabulated the levels of reported jubatus, declined at 5.03% (SE = 0.25%) anthropogenic sources of mortality (sub- per year, statistically significant rates (P < sistence, incidental take in fisheries, and 0.10) in all but the eastern Aleutian Islands research), estimated another (illegal shoot-region. The greatest rates of declines oc-ing), then approximated levels of predation curred in the eastern and central Gulf of Alas-(killer whales and sharks). We attempted to ka and the western Aleutian Islands (> 8.2% partition the various sources of “additional” per year). Using a published correction mortalities as anthropogenic and as addifactor, we estimated the total non-pup pop-tional mortality including some predation. ulation size in Alaska of the western stock We classified 436 anthropogenic mortalities of Steller sea lions to be about 33,000 ani-and 769 anthropogenic plus some predation mals. Based on a published life table and mortalities as “mortality above replace-the current rate of decline, we estimate that ment”; this accounted for 26% and 46% of the total number of mortalities of non-pup the estimated total level of “mortality above Steller sea lions during 1991–2000 was replacement”, respectively. The remaining about 6,383 animals; of those, 4,718 (74%) mortality (74% and 54%, respectively) was are mortalities that would have occurred if not attributed to a specific cause and may be the population were stable, and 1,666 (26%) the result of nutritional stress.

The River Teign SAP Consultation Document

This is the River Teign Salmon Action Plan Consultation document produced by the Environment Agency in 2003. The report pays attention on the external consultation of the River Teign Salmon Action Plan (SAP). This approach to salmon management within the England and Wales introduces the concept of river-specific Conservation Limits as a method of assessing the status of the salmon stock. The River Teign Salmon Action Plan follows the format of those completed for the Rivers Torridge, Taw and Dart. It is the fourth of eight action plans that will be produced for salmon rivers within the Devon Area Fisheries, Recreation and Biodiversity Team. The River Teign SAP contains a description of the river catchment and highlights particular features that are relevant to the salmon population and the associated fishery. The Teign salmon stock is currently failing to meet its conservation limit. This failure is largely attributed to the reduction in the survival rate during the marine phase of the salmon life cycle. This is likely to constrain stocks to lower levels than have existed historically. Still further catch controls may contribute to a reduction in exploitation rates and allow stocks to recover to meet their conservation limit. Other important actions include the continuation of habitat improvement works which aim to maximise spawning habitat utilisation, spawning success, and juvenile survival and production.

Life history of South African snoek, Thyrsites atun (Pisces: Gempylidae): a pelagic predator of the Benguela ecosystem

Snoek (Thyrsites atun) is a valuable commercial species and an important predator of small pelagic fishes in the Benguela ecosystem. The South African population attains 50% sexual maturity at a fork length of ca.73.0 cm (3 years). Spawning occurs offshore during winter−spring, along the shelf break (150–400 m) of the western Agulhas Bank and the South African west coast. Prevailing currents transport eggs and larvae to a primary nursery ground north of Cape Columbine and to a secondary nursery area to the east of Danger Point; both shallower than 150 m. Juveniles remain on the nursery grounds until maturity, growing to between 33 and 44 cm in the first year (3.25 cm/month). Onshore– offshore distribution (between 5- and 150-m isobaths) of juveniles is deter-mined largely by prey availability and includes a seasonal inshore migration in autumn in response to clupeoid recruitment. Adults are found through-out the distribution range of the species, and although they move offshore to spawn—there is some southward dispersion as the spawning season progresses—longshore movement is apparently random and without a seasonal basis. Relative condition of both sexes declined dramatically with the onset of spawning. Mesenteric fat loss was, however, higher in females, despite a greater rate of prey consumption. Spatial differences in sex ratios and indices of prey consumption suggest that females on the west coast move inshore to feed between spawning events, but that those found farther south along the western Agulhas Bank remain on the spawning ground throughout the spawning season. This regional difference in female behavior is attributed to higher offshore abundance of clupeid prey on the western Agulhas Bank, as determined from both diet and rates of prey consumption.

Length-weight relationship of intertidal molluscs from Mumbai, India

A study on the length-weight relationship of common intertidal molluscs from Mumbai showed a high degree of correlation between their length and weight. Most of the molluscs exhibited isometric growth pattern but in some species, allometric growth was found, which is attributed to maturity, nonlinear growth of shell and the ecological conditions. The variations in the growth rate of Gafriarium divaricatum sampled from two geographically separate sites, Bandstand and NCPA, is a result of variation in ecological conditions.

The study of Indian shrimp larvae feeding by enriched rotifer with vitamin C and unsaturated fatty acid (epa, dha) and its effects on growth factors, survival rate and environmental stresses

In this experiment, the feeding of Indian white shrimp larvae by unenriched rotifers (treatment 1) and enriched with highly unsaturated fatty acid (treatment 2) and highly unsaturated fatty acid along with vitamin C (treatment 3) on the growth factors, survival and resistance against salinity and formalin stress tests were studied and their differences with control treatment including newly hatched Artemia nauplii is compared. In this the study four treatments in a completely randomized design with 3 replicates per treatment were used. Farming of shrimp larvae of Zoea II to postlarvae 5 was done in 20 liter plastic bucket. Present results indicated that growth factors and survival rate of stage Zoea II to postlarvae 1 in treatments 1, 2 and 3 improve rather than control in which this case was due to optimal size rotifer rather than Artemia nauplii. Also, treatments 2 and 3 feeding with oil liver cod emulsion enriched rotifer have the highest concentration of DHA (mg/g DW) and the ratio DHA/EPA in which due to have shown the highest growth factors and a significant difference (P<0.05) with treatments 1 and control. The highest survival at stage PL1 were observed in treatment 3 that was enriched with ascorbyl palmitate in which have to the synergistic properties of vitamin C rather than treatments 2, 1 and control and showed a significant difference (P<0.05). But in stage PL5 the highest amount of growth and survival rates were related to control treatment which showed a significant difference (P<0.05) with other treatments that control has higher size rather than treatments 1, 2 and 3. Also, among experiment treatments that the two treatments 2 and 3 due to enrichment had higher growth and survival rates compared with treatment 1 in which their differences have also been significant (P<0.05). In the case of stress tests, results indicated that the highest survival rate has been reported when specimens were offered a diet containing high levels of highly unsaturated fatty acids with vitamin C. So that in stage PL1 in the salinity stress tests 10 and 20 ppt the highest survival rate was observed in treatment 3. As for the second, treatment 2 showed a significant difference (P<0.05) with treatment 3. It is worth mentioning that treatment 3 showed a higher survival rate compared to treatment 2 due to the synergistic properties of vitamin C. The difference between these two treatments with treatment 1 and control was also significant. No significant difference was observed in formalin stress test 100 ppm in this stage between treatments 3 and 2 which shows the highest survival rate. But their difference with treatments 1 and control was significant (P<0.05). Also, in stage PL5 in the salinity stress tests 10 and 20 ppt the highest survival rate was observed in treatment 3 which showed no significant difference (P<0.05) with control treatment. While their difference in the amount of survival rate with treatment 1 and 2 was significant (P<0.05). In this stage, the highest observed survival rate in formalin stress test 100 ppm included treatments control, 3 and 2 among which there were no significant differences (P<0.05). While the difference between these three treatments with treatment 1 was significant.

A study of Rastrineobola argentea in the Ugandan lakes

Increased stocks of mukene Rastrineobola argentea and the subsequent interest in its fishery on Lake Victoria has been attributed to the poor performance of the endemic fishery as a result of introductions into this lake of foreign fish species Lates niloticus and Oreochromis niloticus. R. argentea now remains the only endemic fish species of economic importance ranking second to the Nile perch in this lake. Despite this importance, biological information on the species and knowledge of its fishery is scanty. Preliminary observations on the species in the Ugandan waters indicate that R. argentea feeds mainly on zooplankton (copepods) during daylight hours. Small quantities of aquatic insect larvae/pupae (chironomids and chaoborids) are also eaten mainly at night. These fishes breed just after the rainy seasons and the young eventually mature at between 43-44 mm standard length. Growth and population parameters show a rate of growth (K) of 0.92 with L of 64.5 mm S.L. Natural mortality (M) is given at 2.371 and total mortality (2) of 3.594. Two mesh size nets 10 and 5 mm are in use in the lake. The smaller mesh size which is more preferred by the artisanal fishermen however tends to capture many immature fishes. There is therefore need for a unified lakewide data collection on the species and its fishery in order to obtain more reliable biological information necessary proper management of this fast developing fishery.

A report of the gillnet survey in the Ugandan waters of Lake Victoria under IFMP (January to March 2006)

Under the Implementation of the Fisheries Management Plan (IFMP) for Lake Victoria Result area 4, quarterly gillnet surveys are undertaken to monitor changes in fish stocks and environmental parameters in the shallow nontrawlable areas of the lake For purposes of monitoring surveys, the Ugandan sector of Lake Victoria is divided into 3 zones as shown in Figure 1. During the second quarter of APE2, two gillnet surveys were undertaken in zones 1 and 3 in February and March 2006 respectively. The purpose of the surveys was to monitor changes in the fish stocks and their biological characteristics, water quality, algal dynamics and invertebrate communities; as detailed in the various sections of the report. The surveys followed those conducted in November and December 2006 in the same zones. Results of the surveys showed that the number of fish taxa was higher in the near-shore fleets (0-100m) decreasing towards offshore. The near-shore areas were also associated with high primary productivity and hence secondary production to which Caridina and other invertebrates are part. These organisms are an important source of food for the fish and this may partly account for the high number of fish species recorded in this area of the lake. It was also observed that although Nile perch was the most dominant fish species recorded in all the stations during the surveys, haplochromines, Brycinus sadleri, Brycinus jacksonii Oreochromis niloticus and various mormyrid species contributed significantly to the fish biomass. The presence of many fish species and their coexistence with the predator, Nile perch is attributed to the presence of macrophyte cover and rocky habitats which serve as refugia in the shallow inshore habitats of Lake Victoria. In addition, the vegetated habitats are an important source of food for the fishes. As reported in macro-invertebrate studies, big populations of Caridina and other invertebrates were recorded among macrophyte beds. Caridina is an important source of food for juvenile Nile perch and other fish species so are the other invertebrates especially chironomid larvae, odonata nymphs and molluscs. Resurgence in haplochromine cichlids was observed during the surveys. The presence of haplochromines cichlids in all the sites especially Thruston Bay where it ranked the second by percentage contribution in number, is evidence of the recovery of this group of fishes which had declined largely due to predation by L. niloticus. Caridina nilotica has also increased in biomass and is a major component of the Nile perch diet. This could have reduced predation pressure on the haplochromines by Nile perch and has possibly contributed to recent resurgence in haplochromines cichlids in the lake in the shallow nontrawlable areas of the lake Rastrineobola argentea was found to be an important prey item for Nile perch and other fish species such as Clarias gariepinus. Measures should therefore be taken to ensure sustainable harvesting of Dagaa so that there is enough left to sustain the fishery of Nile perch and other species.

Growth rates of juvenile Nile perch, Lates niloticus L. in lakes Victoria, Kyoga and Nabugabo

The growth rates of Nile perch, Lates niloticus L. of 20 cm to 40 cm total length were estimated in lakes Victoria and Kyoga in 1991 and 1992 and Nabugabo in 1992 and 1993 by tagging. Fish grew faster in Lake Kyoga (mean growth rate 28.7 ± 1.3 cm S.E. per year, N = 49) than in Lake Victoria (18.9 ± 1.4 cm per year, N = 20) and Lake Nabugabo (19.0 ± 0.7 cm per year, N = 43). There were significant differences in growth rates between the lakes (F2 109 = 24.037, P < 0.001). Growth rates in Lake Kyoga were significantly higher than those of lak'es Victoria and Nabugabo (p < 0.001) but those of lakes Victoria and Nabugabo were not significantly different from each other (p = > 0.05). The faster growth rates in Lake Kyoga were attributed to improvement in food supply due to increases in stocks of haplochromine prey. Growth rates in Lake Kyoga were significantly higher, but those of lakes Victoria and Nabugabo were within the ranges of those reported in several native habitats of Nile perch.