Rapid Effects of Marine Reserves via Larval Dispersal

Marine reserves have been advocated worldwide as conservation and fishery management tools. It is argued that they can protect ecosystems and also benefit fisheries via density-dependent spillover of adults and enhanced larval dispersal into fishing areas. However, while evidence has shown that marine reserves can meet conservation targets, their effects on fisheries are less understood. In particular, the basic question of if and over what temporal and spatial scales reserves can benefit fished populations via larval dispersal remains unanswered. We tested predictions of a larval transport model for a marine reserve network in the Gulf of California, Mexico, via field oceanography and repeated density counts of recently settled juvenile commercial mollusks before and after reserve establishment. We show that local retention of larvae within a reserve network can take place with enhanced, but spatially-explicit, recruitment to local fisheries. Enhancement occurred rapidly (2 yrs), with up to a three-fold increase in density of juveniles found in fished areas at the downstream edge of the reserve network, but other fishing areas within the network were unaffected. These findings were consistent with our model predictions. Our findings underscore the potential benefits of protecting larval sources and show that enhancement in recruitment can be manifested rapidly. However, benefits can be markedly variable within a local seascape. Hence, effects of marine reserve networks, positive or negative, may be overlooked when only focusing on overall responses and not considering finer spatially-explicit responses within a reserve network and its adjacent fishing grounds. Our results therefore call for future research on marine reserves that addresses this variability in order to help frame appropriate scenarios for the spatial management scales of interest

The reproductive cycle of the scallop Argopecten circularis (Sowerby, 1835) in relation to temperature and photoperiod, in Bahia Concepcion, B.C.S., Mexico

The reproductive cycle of the scallop Argopecten circularis, an important resource of the fisheries in Baja California Sur, was studied in relation to exogenous factors such as temperature and photoperiod in Bahía Concepción. Monthly samples of adult specimens were used, and biometric data for the shell and soft body parts were recorded. The gonads were analysed histologically and five phases of gonadal maturation were described. This species was confirmed to be functionally hermaphroditic, with a reproductive pattern characterized by a period of maximum activity from December to March, when the dominant phases are maturity and spawning. The prevailing conditions during the main spawning peak were: water temperature between 16 and 22ºC, and photoperiod between 630 and 760 minutes of daily average illumination per month. The first maturation of the gonads, determined histologically, occurred when the organisms had an anteroposterior length of 35 mm. Spawning can occur at 47 mm. The minimum size for maturity and spawning in the general population was 58 mm. We determined that maximum reproductive potential starts at this size, and coincides with the lowest water temperature in the annual cycle. The annual variations in the spawning periods of this species, in different parts of Baja California Sur, suggest flexibility in the influence of exogenous factors and endogenous controls on the reproductive event

Notas sobre el ciclo reproductivo del pectínido manchado Spathochlamys vestalis (Reeve, 1853) en isla Danzante, Golfo de California

Este trabajo documenta algunas notas sobre el ciclo reproductivo del pectínido manchado Spathochlamys vestalis (Reeve, 1853), el cual se desconoce tanto para las costas del Pacífico como del Atlántico. En el Golfo de California es abundante sobre fondos de arena gruesa y entre las espinas de la concha china Spondylus leucacanthus. Es una especie hermafrodita funcional con la porción gonadal masculina separada de la porción gonadal femenina. Se observó alta proporción de individuos maduros durante diciembre de 1994 (87,5%) y en octubre de 1995 (100%). Los individuos desovados se observaron en baja proporción. Se encontró un 5,5% en enero, cuando la temperatura del agua de fondo fue menor de 15ºC y un 5,1% en abril, cuando la temperatura se incrementó a 21ºC. El patrón reproductivo ocurrió de manera continua sin presentar una alta correlación con la temperatura del agua de fondo. La abundancia del fitoplancton fue alta en primavera, si embargo presentó una relación negativa con el desarrollo y la madurez del pectínido (P<0,05)

Reproductive aspects of Octopus hubbsorum (Cephalopoda: Octopodidae) from Espíritu Santo Island, southern Gulf of California, Mexico

Reproductive aspects (spawning season, size and weight at maturity, and fecundity) of Octopus hubbsorum are reported for Espíritu Santo Island, southern Gulf of California (Mexico). A total of 230 octopuses were captured (46% females and 54% males) between June 2006 and June 2007. The sex ratio was not significantly different from 1:1 (P > than 0.05) except in November, when more males were captured than females. Four sexual maturity stages were established for both sexes: immature, maturing, mature, and prespawning (for females) or spawning (for males). The principal spawning season of O. hubbsorum occurred in autumn, when sea surface temperature ranged from 24 to 29 ºC. The size and weight at maturity were 390 mm and 445 g, respectively, for males and 490 mm and 680 g, respectively, for females. The mean potential fecundity was 205,144 oocytes per female and the mean relative fecundity was 309 oocytes per gram of female body weight. Maturing females apparently use substances stored in the digestive gland.