The distribution and further range expansion of non-native blue catfish Ictalurus furcatus in coastal waters throughout the United States Atlantic slope depend, in part, on the salinity tolerance of the fish. However, temperature-mediated sublethal effects of increased salinities on blue catfish biology are not yet known. We assessed the effects of salinity and temperature on growth, body condition, body composition and food consumption of juvenile blue catfish in a controlled laboratory experiment. Temperature and salinity had an interactive effect on blue catfish biology, although most fish survived 112 days in salinities up to 10 psu. At salinities ≤7 psu, mean growth rate, body condition and consumption rates were higher at 22°C than at 12°C. Mean consumption rates declined significantly with increasing salinities, yet, salinities ≤7 psu were conducive to rapid growth and high body condition, with highest growth and body condition at 4 psu. Fish at 10 psu exhibited low consumption rates, slow growth, low body condition and lower proportions of lipids. Habitats with hyperosmotic salinities (>9 psu) likely will not support the full lifecycle of blue catfish, but the fish may use salinities up to 10 psu for foraging, dispersal and even growth. Many oligohaline and mesohaline habitats in U.S. Atlantic slope drainages may thus be vulnerable to establishment of invasive blue catfish, particularly given the increasing temperatures as a result of climate warming.

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Sublethal effects of salinity and temperature on non-native blue catfish: Implications for establishment in Atlantic slope drainages.

Acquisition of biological information on invasive fishes during the early stages of invasion could be critical in orienting subsequent management strategies. To achieve such a task, biological invasion researchers and practitioners take advantage of numerous technologies (e.g. genomics and acoustic telemetry). Surprisingly, the study of invasive fish ecology by analysis of the chemical composition of calcium carbonate hard parts (e.g. otoliths and scales) remains underutilized, despite some convincing examples of successful applications in the scientific literature. Among its most common applications in invasion biology, otolith chemistry has been used to identify natal origins, reconstruct migratory behaviour and assess mixed-stock structure. In this literature review, we provide a general overview of those previous applications but more importantly identify some gaps and obstacles to applications of otolith chemistry in invasion biology and suggest development for innovative applications, including use in wildlife forensic sciences and reconstruction of the early dynamics of invasions. 

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Listening with the invasive fish ear: applications and innovations of otolith chemistry analysis in invasive fish biology

Many present-day aquatic ecosystems are defined by anthropogenic activities such as the introduction of non-native species, habitat loss, and eutrophication. On Prince Edward Island, Canada, non-native rainbow trout (Oncorhynchus mykiss) have established in highly agricultural coastal watersheds. We used acoustic telemetry with continual oxygen and temperature monitoring to explore the relationship between rainbow trout movements, low dissolved oxygen, high temperature, and other environmental parameters in the eutrophic Dunk River estuary. We tested the hypothesis that rainbow trout capitalize on increased productivity from nutrient stimulation but face a trade-off with disturbed water quality. We divided the salinity transition gradient into zones representing the transition from freshwater to seawater and established that temperature and hypoxia increased with salinity. During hypoxic periods, movements decreased, and residence increased in low salinity habitat ( 6 mg L−1, discharge averaging 2 m3 s−1, and temperatures below 23 °C. This study provides insights into the success of rainbow trout in eutrophic estuaries.

Movement of non-native rainbow trout in an estuary with periodic summer hypoxia

There is no standard method to determine the applicability of otolith Sr/Ca ratio to reconstructing estuary use. We have developed a novel method to determine the response of otolith Sr/Ca to changes in water Sr/Ca and salinity in San Francisco Estuary (California, USA). We perform correlated, spatially resolved Sr/Ca and Sr isotope measurements us- ing otoliths from adult striped bass (Morone saxatilis) in the San Francisco Estuary to estimate the otolith-water Sr/Ca partition coefficient (DSr = 0.305 ± 0.009). DSr did not vary significantly with salinity, and therefore the salinity-otolith Sr/Ca model was constructed by substituting the partition coefficient into the nonlinear salinity-water Sr/Ca mixing model for the system. The model demonstrates that the primary factor controlling the response of Sr/Ca to salinity is the Ca concen- tration in the freshwater source flowing into the estuary. A concentration of 60 ppm Ca is an approximate threshold below which estuary Sr/Ca increases rapidly to near the marine Sr/Ca at low salinities (5%-15%), thereby providing sharp delinea- tion of estuary entrance, but little to no discrimination among higher salinity habitats. Our approach provides a general frame- work for assessing the potential utility of Sr/Ca in estuarine systems and specifically for the San Francisco Estuary. Resume ´ : Il n'y a pas de methode standard pour determiner l'applicabilitedu rapport Sr/Ca dans les otolithes pour la re- constitution de l'utilisation d'un estuaire. Nous avons mis au point une nouvelle methode pour determiner la reponse de Sr/Ca des otolithes aux changements de Sr/Ca et de salinitede l'eau dans l'estuaire de San Francisco (Californie, E ´ .-U.). Nous avons obtenu des mesures correlees et a resolution spatiale de Sr/Ca et de l'isotope Sr apartir d'otolithes du bar d'Amerique (Moxone saxatilis) dans l'estuaire de San Francisco afin d'estimer le coefficient de partitionnement otolithe- eau de Sr/Ca (DSr = 0,305 ± 0,009). DSr ne varie pas de facon significative en fonction de la salinite ´; nous avons donc construit le modele salinite ´-Sr/Ca de l'otolithe en substituant le coefficient de partitionnement dans le modele de melange non lineaire de salinite ´-eau Sr/Ca du systeme. Le modele demontre que le facteur principal de controle de la reponse de Sr/Ca ala saliniteest la concentration de Ca dans la source d'eau douce qui se deverse dans l'estuaire. La concentration de 60 ppm de Ca represente le seuil approximatif sous lequel le Sr/Ca de l'estuaire augmente rapidement pour s'approcher du Sr/Ca de la mer asalinites basses (5-15 %), ce qui produit une nette delimitation de l'entree de l'estuaire, mais peu ou pas de discrimination entre les habitats de plus forte salinite ´. Notre methodologie fournit un cadre general pour l'eva- luation de l'utilitepotentielle de Sr/Ca dans les systemes estuariens et en particulier dans l'estuaire de San Francisco. (Traduit par la Redaction)

Evaluating otolith Sr/Ca as a tool for reconstructing estuarine habitat use

Brook trout populations in Prince Edward Island, Canada, have experienced over 50 pesticide-related fish kills since the 1960s. Life history evaluation of large sea-run brook trout recovered following two fish kill events was compared with a reference river using strontium:calcium otolith microchemistry. This study examined the dual hypotheses that anadromous brook trout are more likely to arise from sea-run mothers, and that freshwater entry timing makes them vulnerable to pesticide-induced fish kills. A total 89% of the fish exhibited an anadromous life history, and 77% of these were offspring of anadromous mothers, suggesting that anadromy is dominant in progeny of sea-run mothers. This study adds to our understanding of the maternal inheritance of anadromy in sea-run brook trout populations. Additionally, freshwater entry precedes the majority of fish kill events, illustrating that the overlap between migration and pesticide runoff contributes to the cumulative population risks to sea-run brook trout.

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The Lifetime Migratory History of Anadromous Brook Trout (Salvelinus fontinalis): Insights and Risks from Pesticide-Induced Fish Kills

This study examined the migratory patterns of introduced rainbow trout (Oncorhynchus mykiss) in three rivers in Prince Edward Island, Canada, using acoustic telemetry and otolith microchemistry. On...

Frederick G. Whoriskey

Papers

Otolith microchemistry and acoustic telemetry reveal anadromy in non-native rainbow trout (Oncorhynchus mykiss) in Prince Edward Island, Canada