Ecología y manejo de los lucios muskallonga y europeo: aspectos relevantes y necesidades de investigación Las nuevas técnicas de investigación y los cambios en las pesquerías de los lucios muskallonga, Esox masquinongy y europeo, E. lucius, han contribuido a modificar paradigmas sobre la ciencia y manejo de estas especies. Se llevó a cabo un simposio sobre biología, ecología y manejo de los lucios muskallonga y europeo en la reunión anual de la Sociedad Americana de Pesquerías, en Little Rock, Arkansas, y en un panel de discusión organizado después del simposio se identificaron diversas prioridades de investigación y manejo que incluyen identificación de hábitats de desove, restauración de hábitats y de poblaciones, genética, mortalidad selectiva y explotación. En el futuro, la investigación sobre los lucios muskallonga y europeo se debe enfocar en cuantificar la supervivencia a nivel de huevos y de edad 0; sobre la base de las características del hábitat, evaluar rigurosamente los esfuerzos de restauración de hábitat mediante diseño de sondeos estadísticos, descripción amplia de la estructuración genética de las poblaciones y desarrollar un mejor entendimiento acerca de cómo la mortalidad selectiva y la explotación pueden alterar la estructura de tallas, proporción de sexos y características de la historia de vida de estas especies. Los resultados y la información que se genere tanto de la investigación propuesta como de las prioridades de manejo, serán críticos para la conservación y restauración de las poblaciones auto sostenibles de los lucios muskallonga y europeo.

Accurate age estimates are critical for understanding life histories of fishes and developing management strategies for fish populations. However, validation of age estimates requires known-age fish, which are often lacking. We used known-age (ages 1–25) muskellunge (Esox masquinongy) to determine the precision and accuracy of age estimates from fin rays. We also determined whether fin location (anal or pelvic), fin ray number, and preparation methods affected accuracy and precision. Lastly, we determined whether von Bertalanffy growth parameters estimated from fin ray ages were similar to parameters estimated from known ages. Precision and accuracy of age estimates from anal and pelvic rays were similar and estimates were relatively precise (coefficient of variation = 8.5%) and accurate (mean absolute difference from known age = 0.85 years) for ages 4–15, but ages were overestimated for younger fish and underestimated for older fish. Growth models based on estimated age were similar to models based on known age. Anal and pelvic rays offer a nonlethal alternative for age estimation of muskellunge ages 4–15 and for producing reliable estimates of growth.

Growth is an important metric in fisheries and aquaculture. Growth of small fish over relatively short periods of time is commonly modelled with an exponential function using instantaneous growth rate (g). Instantaneous growth rates are logarithmic and inherently difficult to interpret, but specific growth rates (SGR) express growth as the intuitively understandable per cent change in size per unit of time. A simple metric of SGR (G) is easily computed by exponentiating g, subtracting 1 and multiplying by 100. However, several prominent fisheries publications suggest that SGR should be calculated by simply multiplying g by 100 (we call this G*). A search of the fisheries literature found that the number of papers that used SGR for fish increased significantly from 1830 papers in 2009 to 3170 papers in 2018. An extensive review of 300 papers from this search found that 92.6% were related to aquaculture and only 3.3% of all papers correctly used G to calculate SGR. We algebraically show that G* is fundamentally different than G and cannot be interpreted as a per cent change in weight per unit of time. Furthermore we demonstrate, with three examples from the literature, that using G* as if it were the same as G leads to biologically meaningful underestimates of true growth rates and estimated weights. Given these results and the simplicity with which G can be computed from g, we recommend that fisheries scientists abandon the pervasive practice of incorrectly measuring SGR as 100 times the instantaneous growth rate.

We compared Walleye Sander vitreus egg retention among varying rock treatments placed in a hydraulic flume to test the influence of spawning substrate shape and size on egg retention and the influence of substrate siltation on egg adhesiveness. Egg loss from suboptimal spawning substrates has been hypothesized as a substantial source of mortality during the incubation period. To investigate the influence of substrate size and shape on Walleye egg retention, known numbers of Walleye eggs were pipetted onto rock substrate in a hydraulic flume and exposed to flowing water conditions. Eggs scoured from the substrate during each trial were collected and enumerated. Egg retention was higher in angular crushed limestone than in round glacial till and greater in coarse gravel than in larger size‐classes, under all water velocity regimes. Angular coarse gravel had the highest egg retention rate (mean ± SD, 66.9 ± 3.7%), and round very coarse gravel had the lowest egg retention rate (47.0 ± 3.1%) of all the rock size and shape treatments. Substrate siltation significantly influenced egg adhesion. Clean rocks had a mean ± SD egg retention of 35.9 ± 36.6%, whereas fine‐sediment‐covered rocks did not retain any eggs throughout the course of the experiment. Differences in substrate size, shape, and siltation between Walleye spawning sites may contribute to variation in egg retention rates. Using angular gravel during the creation of Walleye spawning habitat and maintaining clean spawning substrates (through scouring effects and habitat restoration) may decrease mortality associated with egg entrainment and redistribution.Received June 13, 2012; accepted December 12, 2012

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1. Biological invaders can provide a highly abundant novel prey, yet the effect this has on the body condition of native predators is unknown. 2. Since invading the Laurentian Great Lakes over two decades ago, the round goby (Neogobius melanostomus) has become an important food source for many native species. 3. We used long-term data from Lakes Erie and Ontario (1993À2012) to create quantile regression models of mass-length relationships for populations of four native predators: smallmouth bass (Micropterus dolomieu), yellow perch (Perca flavescens), walleye (Sander vitreus) and burbot (Lota lota).Model-based estimates of changes in mass-at-length following the invasion were used to compare the effects of round goby on relative trends in body condition. Water temperature data were also included in the models, to investigate its effects on body condition. 4. The condition of smallmouth bass increased after the invasion, varying in magnitude between lakes and among size classes. Condition of yellow perch changed variably in direction and magnitude, depending on the quantile of the mass-length relationship examined and fish length, whereas that of walleye increased only for larger fish in Lake Ontario. Minor increases in mass-at-length were observed for the smallest length class of burbot, while the body condition of burbot in the largest length class decreased during the study period. 5. Mean summer water temperature did not differ between pre-and post-invasion time periods in Lakes Erie and Ontario, although water temperature was a significant predictor of body condition. 6. Changes in body condition may have implications for additional population and life history characteristics. Future research should investigate the effects of the round goby on growth, age at maturity, fecundity and survival of native predators.

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