Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Information from the logbooks of the longline fleet operating under Mexican flag from 1980 to 1990 was analyzed to determine the tendency of the catch per unit effort (CPUE) of the sailfish fishery. Multivariate analysis techniques (principal components analysis) were used to group the fishing units of this fleet. Time series methods were used to estimate the tendency of the CPUE as an abundance indicator, and this was compared to the behavior of the same index for sailfish sport fishing in Manzanillo, Colima, during this period. The results indicate that the resource is underutilized.

The population of the California sea lion Zulophus californianus (Lesson, 1828) in the Gulf of California during the breeding seasons of the 1980’s was estimated at 23,256 individuals, and 31,393 if census adjustments are applied. Of this total (23,256), 6.9% were adult males, 5.0% subadult males, 40.7% adult females, 23.9% juveniles, 22.7% pups (less than one year of age) and 0.8% were termed miscellaneous. Eighty-six percent of the 29 sea-lion colonies studied were on islands, while the remaining colonies occupied capes of the mainland. However, around 98.8% of the sea-lion population was counted on islands. The number of islands (available habitat) did not determine the sea-lion distribution in the gulf, but the concentration of its usual preys (sardine, anchovy, mackerel and hake) did. Eighty-two percent of the sea-lion population and its pup production took place in the northern region of the Gulf of California (from Isla San Esteban northward), which seems to be associated with the major abundance of small pelagic fish in the gulf. California sea lions tend to inhabit small- and medium-sized islands (less than 3 km in length), which amount for 80% of the sea-lion population. The probable factors that determine the selection of islands this size are: 1) the absence of terrestrial predators, 2) easier communication of breeding animals and 3) sexual selection advantage for mating individuals. The operational sex ratio varied according to island size in a negative exponential trend. More adult females were available per adult males on smaller islands, since reduced space clumped the females. This clumping effect enhances a higher male-male competition (with an evident advantage for males), but also a higher quality of territorial males for the breeding females.

Recognition of the paleoenvironmental significance of biofacies and taphofacies in the fossil record is greatly aided by their study in modern sedimentary environments. Holocene molluscan shell assemblages of Bahia la Cholla, a macrotidal shallow marine environment in the northern Gulf of California, form distinct biofacies and taphofacies whose distribution is controlled by different environmental variables. Biofacies primarily reflect variation in substrate. Distinctive molluscan communities characterize: 1) Salt marsh and innermost tidal flats: organic-rich fine sediments, dominated by epifaunal deposit feeders and deep infauna! suspension feeders; 2) Inner, middle and outer tidal flats: fine to coarse sand, dominated by shallow infaunal suspension feeders; 3) Tidal channel and rocky intertidal zone: hard substrates of shells or rock, dominated by epifaunal algal grazers; 4) Rocky subtidal zone: alternating rock and sand, dominated by attached epifaunal suspension feeders and shallow infaunal suspension feeders. Taphofacies, based on taphonomy of the shallow infaunal bivalve Chione spp., primarily reflect variation in tidal submergence time and current energy. Distinctive suites of taphonomic attributes characterize: 1) Outer tidal flats, rocky intertidal zone, and rocky subtidal zone: environments experiencing prolonged or continuous tidal submergence and high tidal current velocities, characterized by high levels of abrasion, bioerosion by bivalves and clionid sponges, and encrustation by bryozoans; 2) Tidal channel: an environment experiencing continuous submergence and the strongest tidal currents, characterized by very high levels of abrasion, bioerosion by algae, and encrustation by serpulid polychaetes; 3) Sall marsh, inner tidal flats and middle tidal flats: environments experiencing relatively short periods of submergence and low tidal current velocities, characterized by low levels of taphonomic alteration. Biofacies and taphofacies provide different and complementary types of information about the sedimentary environments of Bahia la Cholla. In paleoecological studies, a more complete picture of ancient environments can be generated by integrating taphonomic data with taxonomic and ecologic data.

This study is fundamentally focused on a simple, but relatively unpondered problem: the coral δ18O temperature sensitivity (dδ/dT). Previous paleotemperature studies of corals have involved the use of either: 1) the calcite’s δ18O temperature sensitivity for mollusks (Epstein et al., 1953) or 2) the slope value (Δδ/ΔT) obtained by comparing annual temperature extrema versus annual δ18O extrema in the annual growth bands of coral skeletons. Because both perspectives involve the use of different values for the thermal sensitivity of the coral skeleton, significant discrepancies may be obtained while reconstructing oceanic paleotemperatures. In order to solve this problem, a field calibration was conducted by comparing the δ18O composition of coral skeletons of Porites lobata with sea surface temperature (SST). A paleotemperature equation for P. lobata was determined by comparing the sclerochronologicaly determined monthly skeletal δ18O values with monthly SST values for the Costa Rican coast. Additionally, when δw effects were considered in the coral skeletons, it was found that Porites yields a temperature dependent 18O isotopic fractionation between 0.222 and 0.235‰/ºC. This study reveals that the thermal sensitivity of the coralline aragonite is slightly larger than that for mollusk’s calcite. Therefore, future oceanic paleotemperature applications that involve corals should avoid the use of the thermal sensitivity of the δ18O of biogenic calcite, as has been done in the past. The use of the slope value proposed here may also eliminate the common problem of the seasonal ΔTºC not matching the Δ(δc-δw) observed in the coral skeletons.

A survey on rocky shore mollusks was conducted in some bays of Socorro Island during February and May 1991 and March 1992. Specific richness and composition were analyzed for all expeditions. Relative density and frequency were analyzed only for the last two. The Importance Value Index (IVI) and Jaccard and Morisita similarity indexes were also calculated. Gastropods were the most diverse mollusks in the island, with 23 species in February, 33 in May and 39 in March. Vargas Lozano Bay had the highest total specific richness in all expeditions (25 in February, 30 in May and 33 in March) due to weak waves that produce greater bottom stability, and a great nutrient contribution from the ships that arrive to the island. Playa Blanca NE Bay showed the highest relative density in May (38.9%) and Playa Norte E Bay in March (24.1%). The IVI showed that the same species obtained the highest levels in all bays and expeditions. In May and March, Isognomon janus and Mitrella baccata were the most common species in all bays. Jaccard and Morisita indexes showed three principal assemblies. Grayson, Binners and Braithwaite were the most similar bays, characterized by strong waves and the presence of some tide pools on the shore. The second group consists of Vargas Lozano and Playa Blanca SO Bays which have protected rocky shores. Playa Blanca NE and Playa Norte E Bays form the third group because of their particular conditions; the first one has a well-developed coral reefnext to the beach, and the second one has a narrow supra and intertidal fringe.

The presence of radiolarians in the diatomitic strata of subunit C of the Trinidad Formation (McCloy, 1984) in Baja California Sur, Mexico, is analyzed with a graphic-multivariate model in order to define a biostratigraphic frame and infer paleoceanographic events. Stichocorys peregrina and Didymocyrtis penultimus are the only index species present in the diatomites. Nevertheless, the total faunistic composition indicates that their deposition was principally promoted by upwelling processes which occurred approximately 8 to 5 million years ago, i.e., during the latest Miocene. As time elapsed in this stage, the California Current intensified until it was very evident in the protomouth of the Gulf of California. The age of the Trinidad Formation diatomites indicates that the Pacific Ocean invaded the gulf-mouth region before the tectonic processes (sea-floor accretion and spreading) were established, processes that have opened and outlined the present morphology of the Gulf of California; consequently, the basin which harbored said invasion can be called protomouth.

Different staining techniques of histological slides were tested and modified in order to improve and facilitate the observation of vegetative and reproductive structures that are taxonomically important for genus and species determinations of nongeniculate coralline algae (Corallinaceae, Rhodophyta). Four groups of staining techniques were differentiated from the results: a) dyes with a low affinity for the thallus: mercuric bromophenol blue, toluidine blue “O” and naphthol blue black; b) dyes with a greater affinity for the thallus: ruthenium red and red “O” oil; c) combined dyes which allowed a better staining of the thallus: naphthol blue black combined with PAS test (Periodic Acid Schiffs reagent) and toluidine blue “O” combined with sodium tetraborate; d) the dyes that gave the best staining results were: Harris’ hematoxylin, Mallory’s phosphotungstic hematoxylin, potassium permanganate (KMnO4). PAS test and safranine-fast green.

Quality evaluation tests were done on the strain of Artemia Las Cumaraguas, Paraguaná, Venezuela, in terms of cyst and naupliar (Instar 1) biometrics, as well as percentage, efficiency, rate and productivity of hatching. Bi-monthly sampling of cysts was carried out from January to September 1991. Simultaneously. temperature and salinity were measured. Average hydrated cyst diameter was 238.14 µm (s.d. ± 0.012). Average length of the nauplii (Instar 1) was 438.69 µm (s.d. ± 0.028) and average chorion thickness 1 1.36 µm (s.d. ± 0.012). Average hatching percentage and efficiency were 81.25% (s.d. ± 3.27) and 203.505 naupliiig (s.d. ± 20.95), respectively. As to hatching rate, T90 was observed at 24.14 hours and the hatching synchrony was obtained at 10.7 hours. Hatching productivity ranged from 184.3 to 354.53 mg/g of cysts. Results reveal the potentiality of Artemia from Las Cumaraguas and its possible use in aquaculture.

A study on benthic marine algae collected from four locations in Ejido San José, Baja California, Mexico is presented. The floristic list includes information on the reproductive stage of the species present in the study area, sea level, substrate and epiphytism. A total of 84 genera with 136 species were recorded, of which 12 are Chlorophyta, 22 Phaeophyta and 102 Rhodophyta. Rhodophyta dominated in terms of diversity over the other two divisions.

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