Multiple annual ovipositions of Cancer setosus along a latitudinal cline: aquaria experiments and analysis of field data

Ovigerous females of Cancer setosus are present year-round throughout most of this species extended distributional range along the Chilean/Peruvian Pacific coast (46°S 2°S). However, their annual number of egg-masses remains speculative and as such hasnt been considered in latitudinal comparisons of this species reproduction. To reveal the effect of temperature on egg-mass production and egg-development female C. setosus were held in through-flow aquaria under natural seasonal temperature conditions (16 23 °C) in Antofagasta (23°S), Northern Chile (06/2005 - 03/2006), and at three fixed temperatures (09/2006 - 02/2007) in Puerto Montt (41°S), Central-Southern Chile. Female crabs uniformly produced up to 3 viable egg-masses within 4 1/2 months in Antofagasta and in Puerto Montt (at 19.3 °C). The second oviposition followed the first, and the third the second, after 62.5 d (± 7.6, N = 7) and 73.5 d (± 12.5, N = 11) in Antofagasta and 64.4 d (± 9.8, N = 5) and 67.0 d (± 2.8, N = 2) in Puerto Montt. At the two lower temperatures in Puerto Montt of 15.9 °C and 12.1 °C the production of a second egg-mass was observed after 82.8 d (± 28.9; N = 4) and 137 d (N = 1) respectively. The duration of egg- development from oviposition until larval hatching decreased from 65 d at 12.5 °C to 22.7 d at the observed upper temperature threshold of 22.0 °C. Based on the derived relationship between temperature and the duration of egg-development (y = 239.3175e-0.107x; N = 21, r2 = 0.83) and reports on monthly percentages of ovigerous females from field studies the annual number of egg-masses of C. setosus was calculated. This analysis revealed an annual output of about one egg-mass close to the species northern and southern distributional limits in Casma (9°S) and Ancud (43°S), respectively, while around Coquimbo (29°S) about two and in Concepción (36°S) more than 3 egg-masses are produced per year

Fisheries assessment of Callinectes arcuatus (Brachyura, Portunidae) in the Gulf of Nicoya, Costa Rica

The Callinectes arcuatus population of the Gulf of Nicoya and its current level of exploitation were investigated based on size frequencyanalysis of trap and trawl catches. Von Bertalanffy growth parameters (K= 0.89; CW∞ = 142mm for males) are in the range reported for otherspecies of this family and suggest that the male size at first maturity (CWmat = 94.3 mm) is reached in about a year. Total and natural mortality(Zyr = 2.49; Myr = 1.32) were derived from catch curve analysis and age at first maturity, respectively, and indicate that the stock is below fullexploitation (E = 0.47). A yield per recruit analysis suggests that yield could be maximised, if E was increased to 0.7 under the preconditionthat recruitment was independent of stock size. Until this has been verified, the use of a precautionary exploitation rate (E0.1) of 0.57 is advisedallowing for a 20% increase in fishing effort (from 300 traps currently being fished to around 360 traps). A maximum effort of 1600 traps,as recommended by the Instituto Costarricense de Pesca y Acuicultura (INCOPESCA), is unlikely to be sustained by the population, since adecrease in the proportion of large males in the catches has already been observed over the past years under the current fishing regime. Thisresource is as yet only sold locally, but present catches of around 145 t seem to already cause market saturation. A greatly increased catch(at E > 0.57) would thus not only be detrimental to the stock but also to the market price of the resource. Future developments of the fisheryshould be based on a co-management approach and should involve the exploration of new market opportunities such as the soft crab market

Auswirkungen von Temperaturvariabilität auf die Fortpflanzung und frühe Lebensstadien von dem brachyuren Krebs Cancer setosus im Humboldtstrom-Auftriebssystem

The cold Humboldt Current (HC) allows for a wide distribution range of the crab Cancer setosus MOLINA, 1782 along the Pacific Coast of Peru and Chile (~2 degrees S to 46 degrees S). Life of this cold-water adapted brachyuran crab in the HC is challenged by high interannual temperature variability influenced by El Nino Southern Oscillation (ENSO). Early life-history stages may be particularly sensitive to abrupt changes in temperature and may thus represent physiological bottlenecks in species distribution. The present study aims at identifying the effects and limits of latitudinal and ENSO temperature variation on reproduction and early life history traits of C. setosus. The number of annual ovipositions was calculated from monthly frequencies of ovigerous females and the temperature dependent duration of egg development (65 days at 12 degrees C to 23 days at 22 degrees C). In Ancud, Chile (41 degrees S) one annual clutch is laid in late winter, while in Concepcion (36 degrees S), slightly higher winter temperatures (12 degrees C vs. 10 degrees C in Ancud) enable for reproduction throughout the year (~3.6 clutches per year). However, towards the species northern range the annual number of clutches decreases to ~2 in Coquimbo (29 degrees S) and ~1 in Casma (9 degrees S), which is attributed to an increase in metabolic costs of life under warmer conditions. Temperature dependent changes in the reproductive cycle were confirmed by observations on crabs reared in aquaria in Antofagasta (23 degrees S, 16-22 degrees C) and in Puerto Montt (41 degrees S, 12, 16 and 19 degrees C) for up to 10 and 5 months, respectively. The decreasing interbrood periods at higher temperatures are accompanied by a decrease in the energetic investment per offspring. Eggs laid at low temperatures in Puerto Montt (~11 degrees C) contained 32% more energy, measured as dry mass, carbon, nitrogen, and fatty acid content and volume, than eggs of equal sized females produced at ~19 degrees C in Antofagasta. However, when exposed to warmer temperatures, seasonally in the field and under aquaria conditions, females in Puerto Montt went on to produce smaller eggs in subsequent egg masses. The larger investment per offspring at lower pre-oviposition temperature is discussed to be adaptive by providing the hatching larvae with a higher amount of energy needed for their prolonged development at lower temperatures. Female investment in egg traits is not carried over 1:1 into larval traits. Throughout egg development almost twice as much of the total of fatty acids was used for metabolism in eggs incubated at 12 degrees C compared to 19 degrees C (-1.12 and -0.62 microgram/egg, respectively). The observed high degree of reproductive plasticity is discussed as a key to the species' wide distributional range and to sustaining exploitable populations under conditions of high and unpredictable environmental stochasticity. However, the current level of uncontrolled fishing pressure and the low enforcement of the minimum legal size of 120 mm carapace width (CW) have caused Chilean C. setosus catches to decline for more than a decade. Next to a strict enforcement of the minimum CW, the creation of no-fishing areas is recommended, for (i) allowing recovery of the stock and maintaining larval supply, (ii) studying population dynamics and the ecological role of this benthic predator in the absence of fisheries mortality, and (iii) preventing likely long-term effects of size selective extraction of large, fast-growing specimens on the populations gene-pool ('fisheries-induced evolution')

Temperature effects on reproduction and early life-history traits in the brachyuran crab Cancer setosus in the Humboldt Current System

The cold Humboldt Current (HC) allows for a wide distribution range of the crab Cancer setosus MOLINA, 1782 along the Pacific Coast of Peru and Chile (~2 degrees S to 46 degrees S). Life of this cold-water adapted brachyuran crab in the HC is challenged by high interannual temperature variability influenced by El Nino Southern Oscillation (ENSO). Early life-history stages may be particularly sensitive to abrupt changes in temperature and may thus represent physiological bottlenecks in species distribution. The present study aims at identifying the effects and limits of latitudinal and ENSO temperature variation on reproduction and early life history traits of C. setosus. The number of annual ovipositions was calculated from monthly frequencies of ovigerous females and the temperature dependent duration of egg development (65 days at 12 degrees C to 23 days at 22 degrees C). In Ancud, Chile (41 degrees S) one annual clutch is laid in late winter, while in Concepcion (36 degrees S), slightly higher winter temperatures (12 degrees C vs. 10 degrees C in Ancud) enable for reproduction throughout the year (~3.6 clutches per year). However, towards the species northern range the annual number of clutches decreases to ~2 in Coquimbo (29 degrees S) and ~1 in Casma (9 degrees S), which is attributed to an increase in metabolic costs of life under warmer conditions. Temperature dependent changes in the reproductive cycle were confirmed by observations on crabs reared in aquaria in Antofagasta (23 degrees S, 16-22 degrees C) and in Puerto Montt (41 degrees S, 12, 16 and 19 degrees C) for up to 10 and 5 months, respectively. The decreasing interbrood periods at higher temperatures are accompanied by a decrease in the energetic investment per offspring. Eggs laid at low temperatures in Puerto Montt (~11 degrees C) contained 32% more energy, measured as dry mass, carbon, nitrogen, and fatty acid content and volume, than eggs of equal sized females produced at ~19 degrees C in Antofagasta. However, when exposed to warmer temperatures, seasonally in the field and under aquaria conditions, females in Puerto Montt went on to produce smaller eggs in subsequent egg masses. The larger investment per offspring at lower pre-oviposition temperature is discussed to be adaptive by providing the hatching larvae with a higher amount of energy needed for their prolonged development at lower temperatures. Female investment in egg traits is not carried over 1:1 into larval traits. Throughout egg development almost twice as much of the total of fatty acids was used for metabolism in eggs incubated at 12 degrees C compared to 19 degrees C (-1.12 and -0.62 microgram/egg, respectively). The observed high degree of reproductive plasticity is discussed as a key to the species' wide distributional range and to sustaining exploitable populations under conditions of high and unpredictable environmental stochasticity. However, the current level of uncontrolled fishing pressure and the low enforcement of the minimum legal size of 120 mm carapace width (CW) have caused Chilean C. setosus catches to decline for more than a decade. Next to a strict enforcement of the minimum CW, the creation of no-fishing areas is recommended, for (i) allowing recovery of the stock and maintaining larval supply, (ii) studying population dynamics and the ecological role of this benthic predator in the absence of fisheries mortality, and (iii) preventing likely long-term effects of size selective extraction of large, fast-growing specimens on the populations gene-pool ('fisheries-induced evolution')