Guillermo Rodríguez-Domínguez

Estimation of Individual Growth Parameters of the Cortes Geoduck Panopea globosa from the Central Gulf of California using a Multimodel Approach

ABSTRACT We describe the growth of the Cortes geoduck Panopea globosa (Dall 1898) in the Central Gulf of California using a multimodel approach. Geoducks were collected from November 2008 to February 2010 as part of an experimental fishery off Guaymas, Sonora, Mexico. Their age was established using the acetate peel method. Individual growth was estimated by means of 4 models: von Bertalanffy, logistic, Gompertz, and Schnute. The parameters in each model and their confidence intervals (CIs) were computed using the maximum likelihood method. The best-fitting model was selected using Akaikes information criterion (AIC). According to the AIC, the logistic growth model best describes the growth of P. globosa in this region. We recomputed the CIs of the best model through bootstrapping the model 1,000 times. We found that the asymptotic length of the shell of P. globosa off Guaymas (located in the Central Gulf of California) was 122.2 mm (95% CI, 116.3–128.1) by averaging the asymptotic length estimated in the 3 candidate models (Schnute was not supported). After bootstrapping, the values for the parameters and the first-order corrected 95% CI of the logistic model were L∞ = 122.16 (118.2–124.94), K = 0.497 (0.36–0.614), and t0 = 2.26 (1.599–2.571). We concluded that using a multimodel approach and the AIC represent the most robust method for growth parameter estimation, at least in the studied species.

The interannual variability of size at maturity of the brown crab Callinectes bellicosus Stimpson, 1859 (Brachyura, Portunidae) in the Gulf of California

This study examines how the size at maturity (CW 50% ) of Callinectes bellicosus Stimpson, 1859 is affected by environmental variability and by the source of the data. The samples were obtained from a coastal lagoon in the eastern Gulf of California between 2000 and 2003, and in 2011. To explore for interannual variation in environmental conditions, an extended negative power-law model was used, with SSTa as the annual sum of monthly sea surface temperature anomalies and Chl-a as the monthly chlorophyll a mean in a year. The interannual variability in the CW 50% of C. bellicosus was also calculated. We found that the percent of mature female drives inter-annual variability in CW 50% and that the addition of Chl-a to the model does not contribute further to the explanation of this phenomenon. The hypothesis that environmental variations affect the reproductive dynamics of the stocks needs to be tested in this species in another area.

Species composition and timing of penaeid shrimp postlarvae (Decapoda, Penaeidae) in two zones of the Mexican Pacific coast

The species composition and variation in density (postlarvae m−3) of penaeid shrimp postlarvae were surveyed every 14 days in two zones of the Mexican Pacific coast; in the north (Mazatlan, 23°N 106°W) and south (Gulf of Tehuantepec, 15°N 95°W). Sampling coincided with full moon and new moon, and they were carried out with plankton net (0.3 m mouth diameter and 450 μm mesh size). Average sea surface temperature (SST) for 1985-1995 increased from Mazatlan (26.2 ± 0.2°C) to Tehuantepec (28.3 ± 0.5°C). The difference in SST between the coldest and warmest month was 7.8°C in Mazatlan and 3.3°C in Tehuantepec. Four species of penaeid shrimp postlarvae were identified: Litopenaeus vannamei (Boone, 1931), L. stylirostris (Stimpson, 1874), Farfantepenaeus californiensis (Holmes, 1900) and F. brevirostris (Kingsley, 1878). There was a regional variation in the species composition. L. vannamei was abundant at both coasts with 40% and F. californiensis varied from south to north from 45 to 36%; the less representative species were L. stylirostris and F. brevirostris, which varied from south to north from 15 to 24%. The occurrence period near Mazatlan is seven months, and it is year-round in Tehuantepec. This study suggests that warm water and low seasonal SST variability facilitate the presence of the shrimp larvae over a longer period.

Analysis of crab size structure and the fishing effort applied to a crab fishery in northwest Mexico

The fishing effort of a Sinaloa crab fishery in the Gulf of California in 2014 was analysed based on fishermen’s interviews, official catches and permits, and information from a sample of fishing logbooks from five fishery cooperatives operating in four coastal lagoons that contained the daily catch from individual fishing trips. Unauthorized gear, a double-ring net (DR), was used most frequently (>70% of the fishers) for crab fishing, although authorized single-ring nets and Chesapeake traps (CT) were also used with low frequency. The estimated fishing effort was 641 boats/day in the four coastal lagoons, which was 34% more than authorized, and 818 boats/day were employed in all of Sinaloa. A total of 57 479 fishing gears were estimated for the study area, which was 49.9% greater than the maximum authorized number, and 80 822 nominal fishing gears were estimated for the entire Sinaloa crab fishery, 14.15% more than the total gear limit (70 800). The size of the mesh used in the gear was smaller than the authorized limit of 76 mm, and >50% of the catches included crabs of unlawful size. It is argued that the effort must be regulated in terms of the number of vessels, per unit time, and not the number of gears. The information from this study demonstrates a failure to monitor compliance with current regulations and thus means that other strategies for the sustainable management of the fishery, such as co-management, should be tested.

COMPARISON OF GROWTH CURVES OF FOUR PANOPEA SPECIES

ABSTRACT In this study, Kimuras likelihood ratio test was used to compare growth curves for Panopea generosa, Panopea globosa, Panopea zelandica, and Panopea abbreviata. The curves were generated from previous studies using the von Bertalanffy growth model (VBGM). Geoducks P. generosa and P. globosa are distributed throughout the northern hemisphere; the other two species are found in the southern hemisphere. Individual parameters were used from the VBGM for each species from previously published resources to calculate the average length-at-age (Lti) data for intervals of 1–20 y. In this study, any Lti estimated for any of the species was considered as data to fit a global model and to compute error estimation. The average asymptotic lengths were 147.5 mm, 142.7 mm, 111.1 mm, and 102.5 mm, respectively, for each species listed earlier. These findings provided good evidence that the northern hemisphere species, P. generosa and P. globosa, are the largest and had no significant differences in length between them. The species from the southern hemisphere (P. zelandica and P. abbreviata) were the shortest, with a significant difference in length between them. Three of the four species analyzed inhabit the Pacific Ocean, with only P. abbreviata, the smallest of the four geoducks studied, being endemic to the southwestern Atlantic.

Catch—Maximum Sustainable Yield Method Applied to the Crab Fishery (Callinectes spp.) in the Gulf of California

ABSTRACT The objective of this study was to determine the maximum sustainable yield (MSY) of the crab fishery in the Gulf of California by applying the catch-MSY method. This fishery occurs in two states—Sonora and Sinaloa, along the mainland coast of the Gulf of California—and involves two species: Callinectes hellicosus and Callinectes arcuatus. The main species supporting the fishery in both states is C. bellicosus, whereas C. arcuatus accounts for 5% of crab catches in Sonora and 20%–30% in Sinaloa. The catch-MSY method uses a set of viable r–k combinations to approximate MSY. The r–k combinations are the carrying capacity k and the maximum rate of population increase r for a given stock in a given ecosystem, which are required in most production models, such as the Schaefer model, to estimate MSY. Prior carrying capacity in this study was set arbitrarily from the maximum catches in a series evaluated to 100 times the maximum catch. This range ensures the real carrying capacity could be determined if catches were at MSY sometime during the period evaluated. Maximum potential could have been realized since 2006 for the Sinaloa stock and since 1996 for the Sonora stock. The evidence for these facts is that the catch per unit of effort decreased, and reductions were observed in the mean size of individuals; these changes occurred in the Sinaloa crab fishery. All methods devoted to management procedures of fisheries stocks entail a number of criticisms, and estimations of carrying capacity and stock biomass are costly; however, because sustainable fisheries are desired and data-poor stocks are common, a simple method like catch-MSY has proved be useful in the management of the crab fishery in the Gulf of California.

Aquaculture Research and Development as an Entry-Point and Contributor to Natural Resources and Coastal Management

Recent, fervent international dialogue concerning the existence and magnitude of impacts associated with aquaculture has had both positive and negative outcomes. Aquaculture stakeholders have become sensitized to requirements for improved environmental management of aquaculture. On the other hand, in some cases aquaculture development has been negatively affected by some of the unwarranted and unproved allegations to the detriment of the stakeholders most in need of aquaculture development (i.e., resource users, particularly the poor, who are dependent on natural resources). These resource users are targeted by, and directly influence biodiversity and conservation agendas; hence the need to understand how to gain their active participation. This discussion focuses on examples of how aquaculture research and development can be a useful tool or strategy for resource management initiatives and provide tangible positive including increased stakeholder participation and cooperation, offering alternatives to resource extraction and use in otherwise difficult or intransigent resource management conflicts.

Reproductive traits and relative gonad expenditure of the sexes of the free spawning Chiton articulatus (Mollusca: Polyplacophora)

ABSTRACT Reproductive studies of an intertidal free-spawning population of Chiton articulatus (Mollusca: Polyplacophora) from Puerto Angel, Oaxaca, Mexico were undertaken during 2011. We used gonad histology and gonadal indices to assess the relative gonad expenditure of the sexes (RGES) and other reproductive traits, accounting for individual and seasonal variation within this population. At this location, C. articulatus is gonochoric, without sexual dimorphism, except internally by gonad colour (testis is ‘salmon’ coloured and ovary olive green). Annual and monthly sex ratios (m/f) do not differ significantly from 1:1. Highest population-level gonadosomatic index (GSI) corresponded to maximum (peak) ripe stage (i.e. maximum gonad investment), with a first peak in May with a high value (8.4 ± 0.5) and a second peak during August-September with a lower value (4.7 ± 0.3). GSI fluctuated throughout year implying that gonad expenditure may be seasonally constrained, but with overall synchrony between sexes of ripe and spawning stages. July to December was the main reproductive season with some facultative spawning occurring off-season. Ripe and spawning RGES did not differ between sexes, suggesting that either sperm competition is intense and/or that sperm limitation is high. Early spawning individuals may quickly replenish their gametes for a second phase of gamete release later. Abbreviations: RGES: relative gonad expenditure of the sexes; GSI: gonadosomatic index; GDS: gonad developmental stages; MiMI: microscopic maturity index; SST: sea-surface temperature.

Effect of tidal hour on the abundance of penaeid shrimp postlarvae (Decapoda, Penaeidae) along the Mexican Pacific coast

In the present study we explored the effect of the tidal hour on the postlarvae abundance of the penaeid white-leg shrimp ( Litopenaeus vannamei (Boone, 1931)) in three Mexican Pacific coastal lagoons. Correlation analysis of tidal hour against the hourly variation of the abundance of postlarvae was conducted in three regions of the Mexican Pacific; the system lagoon Huizache-Caimanero LHC, the region of the “Grandes Lagunas” SGL and the “Mar Muerto” Lagoon LMM. Two peaks were found in L. vannamei abundance in the three locations, at 04:00 and 16:00 of tidal hour in LHC and SGL, and 06:00 and 12:00 of tidal hour in LMM. Significant correlations between postlarvae and the tidal hour for the three regions were found. The tidal hour standardizes the time of ebb and flow. It is concluded that tidal hour can be used as cue for shrimp postlarvae immigration to nurseries.

Potential distribution of Geoduck clam Panopea globosa of the Gulf of California in a climate change Model

El cambio climatico ha roto el equilibrio natural y se ha modificado el estado de salud de las diferentes especies comerciales como la almeja de sifon. Por lo tanto, el objetivo del presente estudio fue pronosticar la distribucion de almeja de sifon Panopea globosa del Golfo de California en el ano 2050 ante un escenario de cambio climatico. Se uso el modelo de maxima entropia (MaxEnt) utilizando 12 variables ambientales que afectan la distribucion desde el punto de vista termico, quimico y biologico. El modelo de MaxEnt predijo el habitat potencial adecuado para P. globosa con altas tasas de exito ( Area Under the Curve [AUC] = 0.995). El habitat mas favorable de P. globosa se encuentra en Guaymas, Sonora, debido a la surgencia de nutrientes que benefician la produccion de clorofila-a. Para el ano 2050, el modelo MaxEnt pronostico que en Sonora se presentara una reduccion hacia la costa sur. En Santa Rosalia e Isla San Marcos, Baja California Sur, las probabilidades disminuyen de 0.70 a 0.04. Los actuales sitios de captura se notaran alterados con posibles afectaciones sociales y economicas en las comunidades litorales. La conclusion es que el estudio resulta importante para la administracion de recursos pesqueros, ya que en un escenario de cambio climatico los sitios de captura pueden modificarse.