Otoliths are calcified structures located in the inner ear of teleost fish. They are formed by the crystallisation of calcium carbonate in the form of aragonite onto a protein matrix. Otoliths grow continuously during the lifespan of the fish by the deposition of concentric layers of aragonite and protein. During the formation of otoliths, trace elements are potentially incorporated into the otolith either by substitution for Ca or through co-precipitation with other carbonates. Since it has been suggested that otolith composition is reflective of the external environment (i.e. food and/or water) otoliths have been used as a temporal record to address many fisheries questions. Generally, toxicological studies focus on soft tissues (e.g. liver, kidneys, muscle) to determine metal exposure in fish. However, interpretation of the metal concentrations can be challenging due to the labile nature of metals in these tissues. A more recent approach to investigate temporal trends of metal exposure involves the use of otoliths. Otoliths are metabolically inert so that, once metals are incorporated they are not subject to remobilization. Red Lake, located in the Canadian Shield in Northwestern Ontario is recognized as a popular fishing area. However, over the last decade lake trout have experienced a drastic decline, with concurrent increase in the age distribution. One hypothesis for the recruitment failure has focused on the metals present in the water as a result of past mining activities. A retrospective analysis of the elemental signatures in the lake trout otoliths was performed to determine whether trace element concentrations have changed in Red Lake over the past three decades. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to determine trace elements in otoliths recovered from lake trout from 1960 to 2008. Mn was incorporated into the otoliths and there was a suggestion that concentrations peaked between 1980 and 1989 in Red Lake. Concentrations of Mn in lake trout otoliths ranged from 0 mg/g to 10.1 mg/g. Potential contributors to the elevated concentrations could have been associated to the local geology. In addition to geology further uncertainties concerning the water and diet to otolith relationships could also contributed to the Mn concentrations. Augmented diets failed to increase metal concentrations in otoliths. Further research is required to further investigate the relationship between Mn in the environment and the incorporation into the otolith.

Otoliths are calcified structures located in the inner ear of teleost fish. They are formed by the crystallisation of calcium carbonate in the form of aragonite onto a protein matrix. Otoliths grow continuously during the lifespan of the fish by the deposition of concentric layers of aragonite and protein. During the formation of otoliths, trace elements are potentially incorporated into the otolith either by substitution for Ca or through co-precipitation with other carbonates. Since it has been suggested that otolith composition is reflective of the external environment (i.e. food and/or water) otoliths have been used as a temporal record to address many fisheries questions. Generally, toxicological studies focus on soft tissues (e.g. liver, kidneys, muscle) to determine metal exposure in fish. However, interpretation of the metal concentrations can be challenging due to the labile nature of metals in these tissues. A more recent approach to investigate temporal trends of metal exposure involves the use of otoliths. Otoliths are metabolically inert so that, once metals are incorporated they are not subject to remobilization. Red Lake, located in the Canadian Shield in Northwestern Ontario is recognized as a popular fishing area. However, over the last decade lake trout have experienced a drastic decline, with concurrent increase in the age distribution. One hypothesis for the recruitment failure has focused on the metals present in the water as a result of past mining activities. A retrospective analysis of the elemental signatures in the lake trout otoliths was performed to determine whether trace element concentrations have changed in Red Lake over the past three decades. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to determine trace elements in otoliths recovered from lake trout from 1960 to 2008. Mn was incorporated into the otoliths and there was a suggestion that concentrations peaked between 1980 and 1989 in Red Lake. Concentrations of Mn in lake trout otoliths ranged from 0 mg/g to 10.1 mg/g. Potential contributors to the elevated concentrations could have been associated to the local geology. In addition to geology further uncertainties concerning the water and diet to otolith relationships could also contributed to the Mn concentrations. Augmented diets failed to increase metal concentrations in otoliths. Further research is required to further investigate the relationship between Mn in the environment and the incorporation into the otolith.

Proefschrift--Utrecht. / "Lijst der aangehaalde litteratuur": p. 157-160.

Sauger Sander canadensis is a native, migratory sportfish found in large rivers and riverine impoundments, primarily in the central United States. The migratory nature of this species requires access to un-impounded sections of river in order to complete reproduction and other aspects of life history. This requirement, along with their popularity as a gamefish, has resulted in widespread declines in sauger populations throughout their range due to habitat alteration and fragmentation combined with harvest pressure. The lower Ohio River supports a sauger population that is impeded by multiple high head dams and is heavily exploited by recreational anglers. However, despite high popularity among anglers, relatively little is known about large-scale movement patterns of sauger in the lower Ohio River. Additionally, the contribution that tributaries make to the population in terms of both recruitment and use by adults has not been assessed. I identified analysis of trace elements and stable isotopes in otoliths as techniques that could help quantify the role that tributary habitats play in the Ohio River sauger fishery. First, I collected water from the Ohio River and its larger tributaries in order to test the null hypothesis that there were no persistent differences in Sr:Ca, δ18O, and Ba:Ca among rivers. Water and otolith Sr:Ca, δ18O, and Ba:Ca from Sander spp. were then compared to test the null hypothesis that there is no significant relationship between Sr:Ca, δ18O, and Ba:Ca in the water and Sr:Ca, δ18O, and Ba:Ca measured in the otolith. I applied this relationship to Sr:Ca, δ18O, and Ba:Ca measured in the core of sauger otoliths collected in four navigational pools to test the null hypothesis that there were no differences in sauger recruitment sources among the four pools sampled on the lower Ohio River. Finally, I analyzed changes in Sr:Ca, δ18O, and Ba:Ca across otolith transects of the same fish to identify movements between the Ohio River and tributary habitats and test the null hypothesis that there were no differences in movement probability by age or assigned origin. Analysis of water chemistry indicated significant differences in Sr:Ca between the Ohio River and its tributaries, but not among tributaries. There were no significant differences in either water Ba:Ca or δ18O between the Ohio River and its tributaries. Comparison of water and otolith chemistry of known origin individuals yielded significant relationships for Sr:Ca and δ18O, but not Ba:Ca. As a result, only Sr:Ca was used for origin and movement assessments. Analysis of otolith core Sr:Ca indicated that tributaries are an important source of recruitment for the lower Ohio River sauger fishery. Otolith Sr:Ca consistent with reaches upriver of the study area were also prevalent in otolith core samples, indicating upriver sources are important for maintaining population density in the study area. Movement analysis indicated high probabilities of movement to upriver habitats in all pools, along with high movement probability to tributary habitats among fish collected in all pools. The data indicated that adult sauger in the lower Ohio river were recruited from multiple sources, and there is a high degree of exchange between the Ohio River and its tributaries. High recruitment and movement probability from upriver areas of the Ohio River indicated that the study area I identified does not encompass all of the river used by the population(s) sampled. Managers should focus on unification of regulations and sampling protocol to reflect this expansive range.

Fluctuation of the seagrass ecosystem may be informative to the impacts of environmental changes. This study focuses on a small, inconspicuous triplefin blenny, Enneapterygius minutus, found in a specific tide pool of seagrass meadow on Gui Wan Bi, Green Island, Taiwan. Its high abundance and stable residence make this species a suitable candidate to monitor the condition of the seagrass ecosystem. Monthly collections were made during low tide from April 2007 to July 2008. The otolith microstructure was examined to study their age and growth circumstance. Developmental stages of the ovaries based on histological characteristics together with data of batch fecundity and GSI value were applied to estimate size at maturation and the spawning seasonality of the individual assemblages in the tide pool. A length-frequency analysis was made by using the monthly data. Enneapterygius minutus is a kind of short life species. It has a quite low batch fecundity and a year-long breeding ability with a seasonal high peak mainly from late winter to late spring. The recruitment of juvenile individuals began about a month after breeding had occurred. These data show that Enneapterygius minutus uses seagrass meadows as a hatching and nursing habitat. According to the close relationship between Enneapterygius minutus and seagrass meadow, it would be possible to monitor this ecosystem by using this species as an indicator when it is under environmental stress.

Southern flounder (Paralichthys lethostigma) populations have declined over the last 25-30 years throughout its range. With this rapid decline, the sustainability of the southern flounder fishery and population viability of this commercially and recreationally important fish has come into question. Previous research conducted in the Northern Gulf of Mexico and North Carolina, has shown that southern flounder often reside in freshwater for significant periods of time during the juvenile life history stage. Juvenile southern flounder have been collected at salinities below 10 in Aransas Bay (TX), suggesting that Texas southern flounder might also have critical periods of freshwater residency. However, the presence of a low salinity residency period in southern flounder in Texas has not previously been tested. Patterns of low salinity residence were determined using otolith microchemistry, using Ba/Ca ratios to determine movements across salinity boundaries. Water samples were collected from the major tributaries to the area in order to establish the Ba/Ca freshwater signature. Otolith Ba/Ca values revealed a high degree of variability in habitat use patterns among individuals. The mean percent time that an individual spent in low salinity habitat was skewed toward the lower end (15%) but a significant proportion of the individuals sampled (59%) used low salinity habitat at some point during their life. The remaining individuals (49%) never entered low salinity habitat. This work indicates that there are two distinctly different groups of habitat use patterns in the population. This work demonstrates that southern flounder in Texas exhibit different habitat use patterns from their congeners in North Carolina and the Northern Gulf of Mexico and can help contribute to the spatial management of the southern flounder population on the Gulf Coast of Texas. / text

The genus Albula includes marine fish species, commonly called bonefish, that occur in tropical coastal ecosystems worldwide. Their association to nearshore marine environments makes bonefish especially vulnerable to habitat loss and overharvest. Artisanal fisheries often harvest bonefish, although, in certain areas, bonefish support lucrative catch-and-release recreational fisheries. Bonefish are largely understudied compared to other economically significant fish species, and the presence of cryptic species within the Albula genus has further complicated the establishment of conservation measures. In particular, there is no detailed biological information available on bonefish from the Red Sea despite the unregulated harvest of bonefish that occurs there. To facilitate the establishment of management and contribute to the overall knowledge of Albula biology, I assessed the genetic diversity, growth, and seasonal reproduction of bonefish in Saudi Arabia. Based on samples collected from local fish markets and coastal waters, my findings provide the first genetically verified records of A. glossodonta in the Red Sea and A. oligolepis in the northwest Indian Ocean. Moreover, my results indicate a genetically distinct Red Sea population of A. glossodonta that reaches smaller sizes than documented for the species in the Pacific Ocean and exhibits distinct seasonal spawning activity over the winter months. This information enables fishery managers to make informed decisions regarding bonefish size limits and seasonal colures around peak spawning activity. My results may become increasingly relevant as the potential for lucrative recreational fisheries for Albula glossodonta will likely increase with the ambitious Red Sea tourism development plans.

Aquatic invasive species are a widespread issue throughout the central United States. Black Carp (Mylopharyngodon piceus) are an aquatic invasive species and are an issue due to their unknown ecological and biological impacts that they may cause to the environment that they invade. Determining movements of an aquatic invasive species such as dam passage or inter-river movement may aid in agency efforts to reduce the spread of an invasive or implement strategies to mitigate its potential expanding range. In this study, I used otolith microchemistry paired with water samples to infer movement and dam passage of Black Carp between eight study regions within the Mississippi River basin. A total of 127 Black Carp otoliths were used and 112 (88%) were classified as immigrants, 14 were classified as potential residents, and one otolith was vateritic so no inferences about movement could be made for that fish. Of the 112 fish classified as potential immigrants, 102 (91%) showed signs of upstream dam passage, and the average instance a Black Carp was inferred to move between rivers was 7 times during their lifetime (SD ± 6.23). These results show that Black Carp may exhibit frequent occurrences of inter-river movement throughout their lives and have high instances of dam passage associated with their movement. This paper presents the first confirming evidence of lock and dam passage by Black Carp, although the apparently expanding range of the species in recent years based on reported captures suggested that lock and dam passage had likely occurred. Evidence of frequent upstream movement and lock and dam passage suggests that future studies should evaluate the efficacy of potential deterrents at locks and dams for preventing or reducing upstream passage by Black Carp.

No description available.

Identifying the natal origin of fish is important to understand connectivity among populations. Capelin, Mallotus villosus, is a key forage fish species that spawns at beach and deep-water habitats along the Newfoundland coast. I investigated the ability to identify the natal habitat of larval capelin using otolith chemical signatures quantified via LA ICP-MS. Otolith signatures of larvae reared under identical conditions were highly variable and classification into treatments was low (~50%). To investigate whether maternal investment was responsible for this variability, artificially fertilized eggs were reared under controlled treatments. Otolith signatures reliably classified individuals into families with high success (83.4%), suggesting maternal investment may confound our ability to identify natal origin. Eggs incubated in water enriched with 137Ba revealed trace elements from the environment are being incorporated into developing otoliths. These findings suggest moderate-high differences in water chemistry and environmental conditions are required to identify the natal origin of capelin. / October 2016