Globally, our knowledge on lake fisheries is still limited despite their importance to food security and livelihoods. Here we show that fish catches can respond either positively or negatively to climate and land-use changes, by analyzing time-series data (1970-2014) for 31 lakes across five continents. We find that effects of a climate or land-use driver (e.g., air temperature) on lake environment could be relatively consistent in directions, but consequential changes in a lake-environmental factor (e.g., water temperature) could result in either increases or decreases in fish catch in a given lake. A subsequent correlation analysis indicates that reductions in fish catch was less likely to occur in response to potential climate and land-use changes if a lake is located in a region with greater access to clean water. This finding suggests that adequate investments for water-quality protection and water-use efficiency can provide additional benefits to lake fisheries and food security.

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Ecología trófica del pez exótico Guatapote del Lerma Poeciliopsis infans (Cyprinodontiformes: Poeciliidae) en el Lago de Pátzcuaro, Región Central de México. Exotic fish species has caused several impacts on aquatic biodiversity. The Lago de Pátzcuaro has some well-studied exotic species, except the Lerma livebearer Poeciliopsis infans. This fish species was introduced into the Lago de Pátzcuaro before 1997 and the aspects of its biology are still unknown. In this study we assessed aspects of the trophic ecology of this exotic fish, P. infans, using gut content and stable isotope analysis to understand its capacity to tolerate anthropogenic environmental degradation in the Lago de Pátzcuaro. We also determined its trophic guild position (TP) using the TrophLab Program and stable isotope. Niche breadth was calculated by standardized Levins' Index (Bi). Fish was captured with a seine during wet and dry seasons at six environmentally different sites and gut contents were obtained. We analyzed a total of 239 gut contents of P. infans. The contribution of each food item in the diet was quantified using frequency of occurrence and area percentage. The importance of each prey item was determined according to the index of relative importance (IRI), and the omnivory index (OI) was used to assess the feeding behavior. Fish were categorized by size and the diet was compared between fish sizes and sites. Dorsal muscle tissue and water hyacinth tissue was obtained for nitrogen isotope signature (δ 15 N) analysis. Additionally, we measured water and habitat quality to evaluate environmental conditions at each site. We concluded that P. infans is an omnivore (OI=0.28) that consumes mainly detritus (44%), epiphytic diatoms (37%), and secondary on terrestrial insects (6%) and zooplankton (10%). The fish can behave as a specialist (Bi=0.39) or generalist (Bi=0.68) and as a primary consumer (TROPH=2.2; TP=2.3) with a feeding strategy that was the same at different sizes, seasons and sites. None of the evaluated sites showed good environmental quality. We argue that P. infans can tolerate changes in water quality and feeding items availability, because it can exploit resources in multiple trophic webs. However, this species could be dependent on habitat complexity, especially in the aquatic vegetation cover.

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We characterized the biotic integrity of the sub‐tropical Duero River, Mexico, comparing current and past index of biotic integrity (IBI) scores with results of an environmental quality index (EQI), inventorying abiotic characteristics and human impacts, and documenting ecosystem changes over the last three decades. We sampled the fish community and measured environmental variables during the dry season of 2009 at 19 sites. We compared 2009 findings with fish data obtained in 1986 and 1991 at nine of the sites. The correlation between the IBI and EQI was high (r2 = 0.79, p = 0.0002), indicating that the IBI accurately characterized environmental condition. Thirteen sites were degraded (68%) based on IBI scores, three were fair (16%) and three had good conditions (16%). Based on the EQI, 12 sites were classified as poor (63%), two as fair (11%) and five as good (19%). A cluster analysis of nine abiotic variables and the IBI values yielded three groups: six sites with good integrity and environmental quality, eight with high chemical oxygen demand and four with high total dissolved solids. A discriminant analysis (square canonical correlation: 0.922, and Wilks' lambda significance: 0.001) identified biochemical oxygen demand, distance to vegetation and total dissolved solids as the main predictors. Compared to 1986 and 1991, 2009 IBI values and ratings had declined significantly (multiple response permutation procedure A = 0.16, p = 0.0005), indicating a trend of environmental deterioration, with scores and ratings at 7 of 9 sites lower in 2009. One site had declined from good to fair, one from good to poor, five from fair to poor, one had remained fair and one had remained good. Degradation was related to excessive human water use, reduced river flows, increased wastewater discharge, deforestation, erosion, and invasive species, and mismanagement of preserved sites (springs), all of which highlight an urgent need to reverse declining environmental conditions. Copyright © 2014 John Wiley & Sons, Ltd.

Significant reductions in the water volume of shallow lakes impose a restriction on species segregation promoting more interactions in the trophic relationships. The diets of three closely related zooplanktivorous silversides belonging to the Atherinopsidae species flock of lake Chapala, Mexico, were analyzed at two sites (Chirostoma jordani, C. labarcae, and C. consocium). Diets were described in critical shallow ( La reducción significativa en el volumen de agua de los lagos someros impone una restricción en la segregación de las especies y promueve una mayor interacción en las relaciones tróficas. Se analizó la dieta de tres especies cercanamente emparentadas de zooplanctívoros pertenecientes al flock de Aterinópsidos del lago de Chapala en dos sitios (Chirostoma jordani, C. labarcae y C. consocium). Las dieta fue descrita en una condición somera crítica (Agosto 2000) y en una condición de recuperación del lago (Agosto 2005). En la dieta se incluyen principalmente cladóceros (Bosmina, Ceriodaphnia y Daphnia) y copépodos (Cyclops). Se detectó una diferencia significativa en la dieta cuando se comparan los años (análisis MRPP, A = 0.22, p < 0.0001) y los sitios en los diferentes años (análisis MRPP, A = 0.17, p = 0.004). De acuerdo a los valores promedio de amplitud de nicho, las especies fueron clasificadas como especialistas y consumidores intermediarios. En condiciones someras, el pequeño intervalo de la amplitud de nicho (1.72 a 3.64) y los altos valores del traslape de nicho (D = 0.64, L = 8.62) indicaron un alto potencial para una interacción explotativa inter-específica. Cuando el lago se recupera en su volumen, un incremento en el intervalo de amplitud de nicho (1.04 a 4.96) y los bajos valores del traslape de nicho (D = 0.53, L = 2.32) indicaron una reducción en la interacción de las especies. La prueba U de Mann-Whitney refuerza este patrón al mostrar una diferencia significativa entre los años para el traslape de nicho (p = 0.006). El incremento en la interacción de las especies durante condiciones de volumen bajo, sugiere una segregación alternativa con variaciones en la historia de vida y en otras dimensiones del nicho como en el caso de la distribución espacial y temporal.

We explore the trophic role that a diverse sympatric group of fishes in the genus Chirostoma play in a large, shallow lake in central Mexico, Lake Chapala. We use δ13C and δ15N stable isotope - based food web analyses to explore how they relate to other components of the Lake Chapala ecosystem. We find five Chirostoma species in top trophic levels of the Chapala food web compared to other fishes, relying on a combination of zooplankton, fish and benthic resources as energy sources. Food web metric analyses showed generally overlapping trophic niches for members of Chirostoma, especially in terms of δ13C. However, C. jordani had lower mean δ15N isotopic values than C. promelas. As a group, "pescados blancos" (C. sphyraena and C. promelas) also had higher δ15N signatures than "charales" (C. consocium, C. jordani and C. labarcae) reflecting greater piscivory, but these differences were not strong for all food web metrics used. Trophic overlap among species of Chirostoma in Lake Chapala raises questions about the forces that might have led to a morphologically diverse but functionally similar and monophyletic group of species.

Reproductive tactics and strategies contribute to the persistence and maintenance of long-term populations in fish species. Members of the subfamily Goodeinae are a group of small-bodied freshwater fish with specialized reproduction (viviparity-matrotrophy). They are found in the highlands of central Mexico, most of them endemic. The aim of this study was to conduct a comprehensive investigation to evaluate the annual reproductive cycle of seven species of goodeines (splitfins). We carried out our study in the subtropical Lake Zacapu, Mexico, with bi-monthly sampling from May 2019 to March 2020. We obtain the fertility, size at first maturity (L50), sex ratio, and gonadosomatic index. Our result shows that populations of goodeines have high fertility compared to other populations of the same species in other aquatic systems and also to other species of goodein. We found that males mature at smaller sizes than females, the observed proportion of females was greater than males in all the goodeines. Lake Zacapu goodeines have two reproductive peaks, one in spring (April to June) and another in fall (September to November). These tactics (fertility rates, sex ratio, reproductive period) and strategies (viviparity-matrotrophy) favor reproductive success in this environmentally stable subtropical lake in the highlands of Mexico.