Abstract Macrobrachium caementarius (Molina, 1782) is the only freshwater prawn that sustains an artisanal fishery in Peru. This study assessed its stock in the Majes-Camaná river by analysing length-frequency data collected by the Peruvian Marine Research Institute. Growth parameters were estimated using the TropFishR and fishboot packages, with asymptotic length ( ) fixed at 130 mm for males and 106 mm for females. Total ( Z ) and natural ( M ) mortality were estimated from the linearised length converted catch curve and the Tanaka and Sekharan empirical relationship, respectively. Yield-per-recruit (YPR) and spawning potential ratio (SPR) analyses were performed. The larger specimens are predominantly males, while females dominate the smaller sizes. Growth coefficient ( K ) and growth performance index ( ) differ between sexes (males: year −1 , ; females: year −1 , ), with males reaching larger sizes, while females grow faster and mature earlier. M was slightly higher in females (0.935 year −1 ) compared to males (0.63 year −1 ), while Z, fishing mortality (F) and exploitation rates (E) were higher in males (1.77 year −1 , 1.14 year −1 , 0.64 year −1 , respectively) than in females (1.32 year −1 , 0.39 year −1 , 0.29 year −1 ). The SPR values suggest that current fishing pressure does not adversely affect the spawning stock, likely due to the limitations imposed by the current closed season and minimum size regulations. The YPR analysis suggests that the current F and E rates are below rates associated with maximum YPR ( and ). Despite these indications of sustainable exploitation, our results suggest that males may become more vulnerable in the future if effort increases, and sex-dependent minimum capture sizes should be established. Furthermore, YPR may be increased by raising the minimum size at first capture for males from 70 to 80 mm through minimum size regulations.
Abstract The smooth fan lobster Ibacus novemdentatus is a promising candidate for aquaculture; however, information on optimal rearing conditions for juveniles remains limited, particularly with respect to digestive performance. In this study, the effects of water temperature on gut transit time were examined in juvenile smooth fan lobsters as an indicator of digestive performance relevant to grow-out culture. Juveniles were fed a formulated diet containing fluorescent polymer microspheres and reared individually at three temperatures (18, 22 and 26°C). Minimum gut transit time was defined as the interval between the commencement of ingestion and the appearance of the first faecal pellet containing fluorescent markers. Feeding success, survival and minimum gut transit time were assessed under both daytime and nighttime conditions. Juveniles readily accepted and ingested the formulated diet at all temperatures. Minimum gut transit time ranged from 167 to 327 min and decreased with increasing temperature, with significantly shorter transit times at 26°C than at 18°C. No significant difference in gut transit time was detected between daytime and nighttime trials. Fluorescent markers detected in the first faecal pellets after starvation indicated that juveniles are capable of evacuating digesta in the absence of a subsequent meal, suggesting that hindgut evacuation is not obligatorily synchronized with foregut emptying. Survival was highest at 22°C followed by 18°C. Mortality increased markedly at 26°C, indicating that this temperature likely exceeds the optimal thermal range for juvenile smooth fan lobsters despite enhanced digestive throughput. Overall, these results suggest that approximately 22°C represents a suitable rearing temperature that balances digestive performance and survival. This study provides the first experimental evidence of temperature-dependent gut transit dynamics in juvenile smooth fan lobsters and offers practical insights for the development of juvenile grow-out protocols in slipper lobster aquaculture.
Abstract The snapping shrimp Alpheus paludicola Kemp, 1915, previously known only from its type locality in India, is reported for the first time from the Sundarbans, Bangladesh. Two specimens from the Hiron Point mudflats were captured and are clearly distinct from all other species of the Alpheus euphrosyne De Man, 1897 and Alpheus microrhynchus De Man, 1897 species complex. This finding extends its known distribution.
Abstract Records of Protohyale macrodactyla (Stebbing, 1899) from Brazilian waters have historically been treated as representing a single widely distributed species. Here, we describe two new species of Protohyale from the Abrolhos Bank, Bahia, Brazil, based on morphological examination of specimens previously identified as P. macrodactyla. Protohyale siriba sp. nov. is characterized by the male gnathopod 2, defined by palm acute with two rows of robust and long setae, palmar corner defined by blunt spine and two short spines, and posterior margin subequal to palm, whereas P. sebastianensis sp. nov. is distinguished by the male gnathopod 2 with basis strongly lobate and propodus massive and ovate, pereopod 7 basis serrate, and epimeral plates 2-3 with the posteroventral corner pointed. Both species differ from P. macrodactyla and other closely related congeners by a combination of characters including adult male gnathopod 2 with palm acute and defined by a palmar corner, and very distinct from posterior margin. Our findings, together with recent descriptions and records from the oceanic islands of Trindade and Saint Peter and Paul Rocks, indicate that Brazilian records previously assigned to P. macrodactyla represent a complex of morphologically distinct species. We also reassess published records from other Brazilian localities, some of which cannot be confidently assigned to P. macrodactyla or to the new species described herein. In addition, Hyale nigra (Haswell, 1879) is reassigned to Protohyale based on morphological evidence. These results reveal previously underestimated species diversity within Protohyale in Brazilian waters and emphasize the need for a comprehensive taxonomic revision of the genus in the region.
Abstract Despite the ecological relevance of podocopid ostracods as paleo- and bioindicators, the combined effects of temperature and salinity on their respiratory physiology have rarely been investigated. New experimental evidence is presented here on the drivers of oxygen consumption in Cypris bispinosa , a common inhabitant of temporary ponds and one of the largest freshwater ostracods in Europe. Closed-cell respirometry measurements were conducted over five experimental runs performed at different salinities (0.03, 0.3, 1, 3, and 6 PSU). Within each experimental run, five replicate groups, each consisting of five adult Cypris bispinosa , were exposed to a sequential, stepwise temperature increase (5 → 10 → 15 → 20 → 25°C). In addition, by compiling occurrence records and associated environmental data, we characterised the conditions under which the species typically occurs, which allows the experimental results to be interpreted within its natural ecological context. As expected, oxygen consumption rates were higher as temperature increased, but there were some significant interactions between salinity and temperature treatments. The highest median OCR value (3.0 μ l O 2 /h per mg) was observed at 25°C and at 1 PSU, a salinity close to those most frequently occupied by the species in nature (0.65 PSU), suggesting that salinity may constrain the capacity of wild individuals to adjust oxygen uptake under warming conditions. These findings expand the still limited physiological information available for freshwater podocopid ostracods and provide a basis for further investigation of their responses to interacting environmental stressors.
