Andy S. Hicks

University of Otago, Taieri, Otago Region, New Zealand

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Publications (7)16.45 Total impact

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    ABSTRACT: Amphidromy is a widespread migratory behavioural syndrome exhibited by fish (and some aquatic invertebrates) that spawn in fresh water and whose larvae migrate to pelagic marine (or lentic) habitats for a period of early growth, followed by a return migration to adult freshwater habitats. The fitness advantage of amphidromy has been the subject of prolonged debate, and we examined the hypothesis that amphidromy mainly increases fecundity through the production of small pelagic larvae. We compared egg size (a proxy for larval size) of closely related non‐migratory and amphidromous fish species in the families Cottidae, Galaxiidae, Eleotridae and Gobiidae. To examine how egg size changes in relation to body size within a taxonomic group, we also compared egg size and maximum body size across most species of New Zealand non‐migratory and amphidromous galaxiids. Non‐migratory species generally have relatively larger eggs than their amphidromous confamilial species. This particular trait has evolved independently several times in each of the four families of amphidromous fish that have given rise to significant freshwater radiations. Amongst the New Zealand galaxiids, mean egg diameter increased with maximum body length for both non‐migratory and amphidromous species; however, despite the considerably smaller relative body size of the non‐diadromous species, the rate of increase in egg diameter relative to the increase in body size is considerably higher in the non‐migratory fish. We propose that amphidromous fish maintain a high level of fecundity by producing small pelagic larvae. In contrast, the relatively large eggs and well‐developed larvae of non‐migratory species increase larval survival in what are often relatively harsh and unproductive freshwater habitats. Consequently, amphidromous species are likely to have a competitive advantage over their non‐migratory relatives when close to a pelagic habitat in which their larvae can grow and develop and then migrate upstream, releasing them from recruitment limitation and giving them a local reproductive advantage over their less fecund non‐migratory relatives. We argue that the persistence and distribution of both life‐history strategies across the landscape depends on the relative difference in the net reproductive return for each strategy in relation to distance from a pelagic larval habitat, as mediated by the relative costs of migration and egg size/fecundity relationships.
    Freshwater Biology 06/2013; 58(6):1162-1177. DOI:10.1111/fwb.12116 · 2.91 Impact Factor
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    ABSTRACT: Complete macrophyte removal to maintain drainage performance in lowland streams can have a negative effect on resident fish communities, but few studies have quantified this impact. Moreover, limited research has been carried out exploring alternative approaches for macrophyte removal that minimise the impact on the resident fish community. The aims of this study were (i) to determine how the current practice of removing almost 100% of available macrophyte cover affects native fish populations in lowland New Zealand streams and (ii) to see whether this impact can be reduced by limiting macrophyte removal to alternating 50-m sections of the waterway. Native fish populations were surveyed before and after experimental macrophyte removal for the following three treatments: (i) complete macrophyte removal, (ii) macrophyte removal from alternating 50-m reaches and (iii) control with no macrophyte removal. Radiotelemetry was used to monitor the behavioural response of individual giant kokopu (Galaxias argenteus) to the different treatments. The results of this study suggest that current drain management practices reduce CPUE of fish by 60%. Although limiting macrophyte removal to alternating 50-m sections did not minimise the community impacts of drain clearing, large giant kokopu did benefit from this strategy. All tagged giant kokopu remained in stream reaches partially cleared of macrophytes, while in completely cleared reaches all individuals were displaced. These results demonstrate the threat current drain management practices pose to New Zealand native fish and highlight the value of trialling alternative methods of macrophyte removal.
    Ecology of Freshwater Fish 10/2012; 21(4). DOI:10.1111/j.1600-0633.2012.00569.x · 1.59 Impact Factor
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    ABSTRACT: Parasite avoidance is increasingly considered to be a potential driving factor in animal migrations. In many marine and freshwater benthic fish, migration into a pelagic environment by developing larvae is a common life history trait that could reduce exposure to parasites during a critical window of developmental susceptibility. We tested this hypothesis on congeneric fish (family Galaxiidae, genus Galaxias) belonging to a closely related species complex sampled from coastal streams in southeastern New Zealand. Migratory Galaxias have larvae that migrate to pelagic marine environments, whereas the larvae of non-migratory species rear close to adult habitats with no pelagic larval phase. Both migratory and non-migratory fish are hosts to two species of skin-penetrating trematodes that cause spinal malformations and high mortality in young fish. Using generalized linear models within an Akaike information criterion and model averaging framework, we compared infection levels between migratory and non-migratory fish while taking into account body size and several other local factors likely to influence infection levels. For one trematode species, we found a significant effect of migration: for any given body length, migratory fish harboured fewer parasites than non-migratory fish. Also, no parasites of any kind were found in juvenile migratory fish sampled in spring shortly after their return to stream habitats. Our results demonstrate that migration spares juvenile fish from the debilitating parasites to which they would be exposed in adult stream habitats. Therefore, either the historical adoption of a migratory strategy in some Galaxias was an adaptation against parasitism, or it evolved for other reasons and now provides protection from infection as a coincidental side-effect.
    Oecologia 01/2012; 169(4):955-63. DOI:10.1007/s00442-012-2251-x · 3.25 Impact Factor
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    ABSTRACT: Parasite infection patterns were compared with the occurrence of their intermediate hosts in the diet of nine sympatric fish species in a New Zealand lake. Stomach contents and infection levels of three gastrointestinal helminth species were examined from the entire fish community. The results highlighted some links between fish host diet and the flow of trophically transmitted helminths. Stomach contents indicated that all but one fish species were exposed to these helminths through their diet. Host feeding behaviour best explained infection patterns of the trematode Coitocaecum parvum among the fish community. Infection levels of the nematode Hedruris spinigera and the acanthocephalan Acanthocephalus galaxii, however, were not correlated with host diets. Host specificity is thus likely to modulate parasite infection patterns. The data indicate that host diet and host-parasite compatibility both contribute to the distribution of helminths in the fish community. Furthermore, the relative influence of encounter (trophic interactions between prey and predator hosts) and compatibility (host suitability) filters on infection levels appeared to vary between host-parasite species associations. Therefore, understanding parasite infection patterns and their potential impacts on fish communities requires determining the relative roles of encounter and compatibility filters within and across all potential host-parasite associations.
    Journal of Fish Biology 08/2011; 79(2):466-85. DOI:10.1111/j.1095-8649.2011.03041.x · 1.73 Impact Factor
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    ABSTRACT: Applying uniform population models and management strategies to widespread species can be ineffective if populations exhibit variable life histories in response to local conditions. Galaxias maculatus, one of the world's most widely distributed fish species, occurs in a broad range of habitats and is highly adaptable, making it an ideal species for examining variation in life history traits across large geographic scales. Here, we examine the spawning biology and early life history of diadromous G. maculatus in coastal rivers in Victoria, Australia, and compare them to other populations throughout its range. We predicted that traits associated with these critical life stages, especially those that respond to environmental conditions that vary geographically, such as seasonal cues and temperature, are likely to vary across large spatial scales. We found that spawning occurs later in Victoria than in New Zealand (NZ) and South America, but migration back to rivers occurs at the same time in Victoria and NZ, but not South America. G. maculatus returning to rivers are also smaller and younger in Victoria than those in NZ. Other traits, like some attributes of spawning schools and spawning habitats, did not vary across large scales. Researchers and managers should be cautious when making broad assumptions about the biology of widely distributed species.
    Marine and Freshwater Research 01/2011; 62(7):790. DOI:10.1071/MF10284 · 2.25 Impact Factor
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    ABSTRACT: In habitats such as estuaries, which are characterised by large and fluctuating gradients in abiotic variables, finding appropriate habitat for successful spawning and egg development can be critical to a species' survival. We explored how salinity requirements for successful fertilisation may govern the distribution of estuarine spawning habitat for the diadromous fish, Galaxias maculatus, which spawns in inundated vegetation on estuary banks during spring tides. Artificial fertilisation experiments confirmed that successful fertilisation only occurs at low salinities (<20). Thus, we predicted that egg distributions would depend upon the extent of low-salinity surface waters in an estuary. Using estuary geomorphology classification schemes, which classify estuaries by physical and chemical characteristics such as their salinity dynamics, we hypothesised that stratified estuaries would provide a greater extent of low salinity surface water than well-mixed estuaries. This prediction was supported by surveys of egg distributions in five estuaries in Victoria, Australia. Eggs were distributed over a greater proportion of 'stratified' v. 'mixed' estuary types. We suggest that combining knowledge of the spawning requirements of a species and physical properties of the habitat, such as those encapsulated in estuary geomorphic classification schemes, can greatly facilitate efforts to identify critical habitats and thus aid in species management and conservation.
    Marine and Freshwater Research 12/2010; 61(11):1252-1258. DOI:10.1071/MF10011 · 2.25 Impact Factor
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    ABSTRACT: An increasing number of studies are uncovering considerable flexibility in migration patterns of diadromous fishes. The development of otolith microchemical techniques has largely driven this research and led to an appreciation of the significance of facultative diadromy in the life history of numerous species. However, validation experiments need to be undertaken for each species and life stage of interest before diadromous migrations can be confidently reconstructed. These validation experiments are required to establish a salinity calibration series against which the otolith microchemistry of unknown individuals can be compared. To facilitate research on facultative amphidromy in galaxiids, we reared the larvae of two species, Galaxias maculatus and G. argenteus, in five different salinities (2, 5, 10, 20, 34). We tested whether trace element signatures of fish reflected their salinity treatment, and hence whether otolith microchemistry could reconstruct diadromous migrations. Distinguishing low salinity (2 and 5) from high salinity (20 and 34) treatments was straightforward using otolith Sr:Ca alone. The five salinity treatments resulted in five distinct multi-trace element signatures for both species (DFA classification success of 85% and 92% for G. maculatus and G. argenteus, respectively). Otolith lithium showed a similar trend to otolith Sr:Ca (ie. higher in saltwater), and otolith Rb:Ca showed a surprising negative trend with salinity despite higher ambient Rb concentrations in saltwater. Our results suggest otolith Li:Ca and Rb:Ca should be considered as part of a multi-trace element approach when investigating diadromous migrations, particularly when non-marine Sr levels may be high.
    Journal of Experimental Marine Biology and Ecology 10/2010; 394(1):86-97. DOI:10.1016/j.jembe.2010.07.018 · 2.48 Impact Factor