Cold Storage of Six Marine Benthic Diatoms Native to the Mexico Pacific Coast

Cultures of six benthic diatoms were maintained in the dark to measure their viability and biochemical composition after 8 wk of storage at low temperature (4 C) in darkness by refrigeration. Cell density, growth rate, and viability for each benthic diatom changed significantly after storage. Significant differences were observed with regard to cell size (length and width) of Nitzschia laevis, Navicula sp., and Amphora tenerrima as a result of storage. In general, the proximal composition of the benthic diatom cultures changed after week 1 of storage and decreased after week 4 of storage for all the diatoms. These results demonstrate that under 1–4 wk of storage these diatoms maintain their viability and had changes in their proximal composition in species‐specific responses. Storage of preserved live microalgae cells is an alternative technique that can be used to reduce the need for continuous maintenance of live cultures and can provide live feed stock for aquaculture applications.     

Fishing operations and adaptive strategies of small‐scale fishers: insights for fisheries management in data‐poor situations

Small‐scale fisheries' management is complex given its multigear, multispecies nature; despite this, fishing effort has usually been controlled by nominal units, ignoring changes in effective fishing effort. This study aimed to understand the adaptive strategies of small‐scale fishers in San Felipe, Yucatan, Mexico through an analysis of their fishing operations. Minor changes in trip numbers among three seasons were observed, but increases in fishing time, depth and travel costs from one season to another at the operational level were found. It was also evident that high value species at the beginning of the season were gradually replaced by low‐value finfish as the season progresses. The results provide insights for new adaptive management strategies according to fisher's adaptive responses. For instance, using boats or fishing trips as fishing effort units in Yucatan may not be the most appropriated unit for management, as fishers adapt their strategies at different levels.     

Growth performance,osmoregulatory and metabolic modifications in red porgy fry,Pagrus pagrus,under different environmental salinities and stocking densities

The effects of two different environmental salinities [brackish water (BW), 12‰; sea water (SW), 39‰] and initial stock densities [low (LD), 1.0 g L^?1; high (HD), 2.0 g L^?1] on growth, osmoregulation, stress and energy metabolism of the fry Pagrus pagrus were investigated over a period of 45 days. Pagrus pagrus (n=80, 5.51 ± 0.25 g mean initial body weight) were randomly divided in eight groups. Growth, weight gain and specific growth rate increased in BW‐acclimated fish compared with SW‐acclimated fish. No differences were observed between the two stock densities tested at either environmental salinity. Plasma osmolality was lowest in BW‐acclimated specimens, but the stock density had no effect on this parameter. Branchial Na⁺,K⁺‐ATPase activity was positively correlated with environmental salinity, but unaltered at the renal level. Plasmatic parameters were enhanced by salinity and stocking conditions. At the hepatic level, triglyceride values were enhanced in BW‐acclimated fish maintained at LD. Muscle metabolites (glycogen, glucose and lactate) increased in BW‐ compared with SW‐acclimated fish; stock density had no influence. Our data suggest that changes in metabolic parameters could be correlated with the higher growth rates observed in P. pagrus acclimated to BW, while no significant effects due to the stocking density used were observed.     

Notes on hatchery spawning methods for bigmouth sleeper Gobiomorus dormitor

The bigmouth sleeper Gobiomorus dormitor, a popular sport fish within its native range, offers a management alternative to exotic species currently managed for recreational fishing. Hatchery production and stocking are needed to create reservoir sport fisheries because this species usually requires access to marine environments for recruitment. Bigmouth sleepers have not been spawned previously in a hatchery, and hence we used natural, artificial and semi‐natural spawning techniques. No egg deposition or propagation resulted from natural pond spawning. Artificial spawning techniques using Ovaprim^® and Chorulon^® injections followed by hand stripping were more successful. Semi‐natural (hormone injections plus volitional spawning) spawning trials using Ovaprim^® and Chorulon^® displayed the greatest potential, and three consecutive evening injections (1.0 mL kg^?1) of Chorulon^® appeared most conducive. High‐fecundity spawning was achieved by injecting bigmouth sleeper pairs and allowing volitional spawning in aquaria with spawning cavities. Initial success in 2007–2008 was isolated to wild‐caught fish, but captive broodstock were spawned using these techniques in 2009. Eggs hatched in <20 h at 23–24 °C. The resulting larvae, 1.0–1.5 mm in length, displayed large yolk sacs, unpigmented eyes and no apparent mouth. These hatchery propagation efforts suggest that hormone‐induced semi‐natural spawning has the greatest potential for bigmouth sleeper propagation.     

Iron,Copper, and Zinc in Some Fish Species of the Atrato River Delta,Colombian Caribbean

The concentrations of iron (Fe), copper (Cu), and zinc (Zn) were evaluated in 96 samples of the following eight fish species: Centropomus undecimalis, Caranx hippos, Scomberomorus brasiliensis, Lutjanus purpureus, Caranx crysos, Megalops atlanticus, Elops saurus, and Epinephelus itajara collected in the Atrato River Delta in the Gulf of Urabá. Three fish were caught from each of the following common fishing grounds: Bahía Candelaria, Bahía Marirrío, Bocas del Roto, and Bocas del Atrato. Fish were captured during a one-year period, with one specimen per species in each climatic period: dry, transient, and wet. The quantification was performed by microwave plasma-atomic emission spectroscopy. The highest levels of Fe and Cu were found in Caranx crysos, and highest level of Zn in Megalops atlanticus. According to the percentage of the daily value per food serving, Caranx crysos and Caranx hippos are good sources of Fe, and Caranx crysos is a good source of Cu.     

Replacement of fishmeal by vegetable meal mix in the diets of Litopenaeus vannamei reared in low‐salinity biofloc system: effect on digestive enzymatic activity

Biofloc (consortium of diverse microorganisms associated to suspending substrates) was developed from waste of shrimp Litopenaeus vannamei postlarvae culture under low salinity (5 g L^?1) to provide an additional nutritious biomass and reduce fishmeal inclusion in feeds in a 28‐day indoor shrimp nursery trial conducted in 15 experimental containers (250 L stocked at 600 org m^?3). Four experimental diets (isoproteic and isocaloric) containing different percentage of fishmeal: 0%, 10%, 20% and 30% substituted by vegetable meal mix (corn, sorghum and wheat) were formulated and elaborated. A control treatment consisted of a commercial feed. The main water quality parameters were monitored, and no significant differences were found among treatments. The growth and survival were similar among treatments. In general, digestive enzymatic activities showed differences being greater in the biofloc system compared with clear water. It was concluded that low‐salinity shrimp nursery could be successfully developed with minimum inclusion of fishmeal in feeds, without significant effect on production response. The adjustment of C : N ratio allowed the increase of microbial biomass in the bioflocs, which contributed to maintain good water quality, provide live food and enhance digestive enzymatic activity of cultured organisms.     

Advances in the study of activity additivity of supplemented proteases to improve digestion of feed protein by Penaeus vannamei

In vitro assays used porcine or bovine trypsin as models of exogenous enzymes to determine functioning in the presence of enzymatic extracts from the digestive gland of whiteleg shrimp Penaeus vannamei. Using electrophoresis and zymograms, when enzymes from the shrimp were mixed in the absence of protein substrate, they hydrolysed the trypsin from bovine or porcine origin. Porcine or bovine trypsin, when mixed with shrimp enzymes in pH‐stat assays in the presence of shrimp commercial feed, fish meal, or casein, there was added activity to hydrolyse the protein substrate. Hydrolysis of protein substrate was twofold to threefold stronger if exogenous enzymes were added. Results suggest that porcine or bovine trypsin could be used as feed supplements for whiteleg shrimp P. vannamei to enhance hydrolysis of proteins in feeds, because the commercial enzymes contributed to the hydrolysis of the protein in the three substrates in the presence of shrimp enzymes.     

The Accuracy of Intraoperative Diagnoses Based on Examination of Frozen Sections A Prospective Comparison with Paraffin-Embedded Sections

The accuracy of diagnoses based on examination of frozen sections was determined by comparing the results to those obtained by examination of tissues prepared using conventional methods (formalin fixation, paraffin-embedded tissue). One hundred ninety-four specimens were examined using the frozen section technique; 37 were examined to confirm a tentative diagnosis or to document lymph node metastasis and the remainder were examined to diagnose an unknown pathologic process. Of the 194 specimens examined, an accurate, specific diagnosis was obtained in 161 (83%); in 19 (10%), the pathologic process was correctly identified, but a specific diagnosis was not obtained; and in 2 (1%) the diagnosis was deferred. The remaining 12 (6%) were incorrectly diagnosed by the frozen section technique. When the number of specimens in which a specific diagnosis was obtained was combined with the number of specimens in which the pathologic process was correctly identified, the overall accuracy rate of the frozen section technique was 93%. There was no difference in the accuracy of the frozen section technique based on the reason for submission of the sample, source of tissue submitted, or the type of pathologic process (i.e., inflammatory or neoplastic). Of the 12 incorrect diagnoses, 4 (33%) were because of sampling errors and 8 (67%) were caused by interpretation errors. The proposed indications for the use of intraoperative frozen sections are: 1) to determine the nature of a pathologic process for which a preoperative diagnosis has not been established, 2) to determine the extent of spread of neoplastic tissue to lymph nodes and other organs, 3) to evaluate resection margins of a neoplastic process, and 4) to clarify situations where a discrepancy exists between the preoperative cytologic or histologic diagnosis and intraoperative gross pathology.