Context is more important than habitat type in determining use by juvenile fish

Bradley, Michael; Baker, Ronald J.; Nagelkerken, Ivan; Sheaves, Marcus

doi:10.1007/s10980-019-00781-3

Cited by 69 publications

(48 citation statements)

References 67 publications

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“…It also provides data on the composition of the fish/nekton assemblage present in the habitats being sampled (e.g. Dunbar et al, 2017), and such data can greatly enhance interpretation and understanding of the processes shaping these communities (Bradley et al, 2019). Complementary data on community composition is usually collected through a variety of sampling approaches such as netting (e.g.…”

Section: Alternatives and Solutionsmentioning

confidence: 99%

Tethering mobile aquatic organisms to measure predation: A renewed call for caution

Baker

Waltham

2020

Journal of Experimental Marine Biology and Ecology

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Tethering experiments are one of the few approaches available to ecologists to assess predation rates in aquatic environments, and they have provided important insights into the processes driving observed patterns in aquatic communities. The potential for experimental artefacts to arise when tethering mobile prey has been well recognised and was vigorously discussed in the literature around 20 years ago. However, we reviewed 128 published studies that tethered fish and mobile crustaceans and found a growing number since that time that we believe do not adequately consider these potential issues. The majority of studies recognise that tethering mobile prey can only provide a relative rather than absolute estimate of predation rates, yet 16% present and interpret their results as if they reflect absolute natural predation rates. Two thirds of published studies at least acknowledge other potential artefacts, less than half test for them, while one third seemingly give no consideration to potential artefacts or biases of the method. Our review also revealed the potential for a lack of independence between individual replicates. More than two thirds of studies deployed replicate tethered prey a minimum of no > 5 m apart, with more than one quarter deploying them no > 1 m apart. Eighty-five percent of studies considered missing prey to represent predation. We deployed 104 tethered fish prey in field trials and monitored them using remote underwater video to determine the causes of prey loss. These trials reinforced the simple but important point that prey missing from tether lines at the end of an experiment can be missing for a variety of reasons other than reflecting predation. They also highlight the potential for underwater video, where it is practical to use, to overcome many of the issues confronting field tethering experiments. Carefully designed tethering studies will continue to be an important tool for ecologists studying patterns of predation in aquatic systems. However, our findings suggest a re-emerging need for researchers to recognise and test for potential biases and artefacts inherent with the technique.

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Section: Alternatives and Solutionsmentioning

confidence: 99%

Tethering mobile aquatic organisms to measure predation: A renewed call for caution

Baker

Waltham

2020

Journal of Experimental Marine Biology and Ecology

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“…The overall value of mangrove forests has been linked to parameters such as geographical location, tidal range (micro-, meso-or macrotidal), setting (coastal, estuarine, island or embayment) and connectivity to adjacent habitats (Unsworth et al, 2008;Igulu et al, 2014;Bradley et al, 2019). While these factors provide important information, this study also shows that for a same mangrove forest, its value is temporally and spatially variable.…”

Section: Discussionmentioning

confidence: 84%

“…Mangrove forests are recognised as important habitats for fish (Robertson and Duke, 1990;Nagelkerken et al, 2002Nagelkerken et al, , 2008. However, their commonly recognised feeding, refuge and nursery value has been shown to be heterogenous and influenced by local environmental factors influencing mangrove forests' accessibility and suitability (Faunce and Serafy, 2006;Bradley et al, 2019). Mangroves can be challenging habitats, especially in regions where they are subjected to tide (Unsworth et al, 2007;Olds et al, 2012), as tidal variation generates a range of constraints.…”

Section: Introductionmentioning

confidence: 99%

Hypoxia in mangroves: occurrence and impact on valuable tropical fish habitat

et al. 2019

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Intertidal mangrove forests are harsh environments that can naturally experience hypoxia in association with low tide. However, we know relatively little about dissolved oxygen (DO) fluctuations and DO-induced responses by fish, although DO is a fundamental water quality parameter. This study examines DO as a potential factor regulating the utilisation of intertidal mangrove forests by fish and consequently their widely recognised feeding, refuge and nursery values. We deployed underwater video cameras, coupled with DO and depth loggers, in a mangrove forest to record changes in fish assemblages in response to tidal variations in DO and other associated environmental parameters. Our results indicate that DO underwent extreme tidal fluctuations, reaching levels as low as 14 % saturation. As DO was identified as a significant factor for explaining variability in fish assemblage composition, we further investigated fish responses to DO fluctuations. Higher taxonomic richness and frequencies of occurrence were observed once DO reached 70 %-80 % saturation. More detailed examination revealed speciesspecific responses. Three distinct patterns of mangrove utilisation in response to DO were identified, driven by apparent taxa's behavioural DO avoidance thresholds. Most taxa did not display any behavioural avoidance, including presence at the lowest DO levels, while other taxa were not observed either below 50 %-60 % saturation or below 70 %-80 % saturation. This implies that tidal migrations, often observed in intertidal environments, could be the result of differential DO tolerances and are not simply initiated by changes in water depth. Taxa remaining in the mangrove forest even at low DO were on average more frequently observed than the other taxa and were mostly species commonly associated with mangrove habitats. This suggests that being adapted to withstand low DO might be an important condition for using mangrove habitats extensively. The need of being tolerant to low DO could constrain fish utilisation and explain the relatively low species richness often observed in other intertidal mangrove forests.

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“…Differences in life history for most of the species, in terms of relative abundances that constitute the differences in the UNYH and GBLEH assemblages, do not point to the UNYH shoreline as degraded in shoreline habitat function, except that the marsh grass associated F. heteroclitus and M. menidia were not as dominant at some sites. Differences include those promoted by larval transport into the estuary from complex coastal hydrodynamic delivery mechanisms (Grothues et al ; Able & Fahay ; Able et al ) and reflect the importance of context as a driver of assemblage differences for similar habitats (Bradley et al ). Nevertheless, comparison with GBLEH provides a semblance of the extent to which diverse juvenile fishes populate shallow shorelines in this region.…”

Section: Discussionmentioning

confidence: 99%

Shoreline infrastructure degradation and increasing littoral naturalization accommodates juvenile fish and crab assemblages in heavily urbanized Upper New York Harbor

Grothues

Able

2020

Restoration Ecology

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Many estuarine shorelines are influenced by urbanization. Extensive shoreline modification in Upper New York Harbor (UNYH) included port development, landfilling marshes, and armoring. Recent sedimentation in constructed shipping terminal embayments, abandonment of shoreline structure maintenance, subsequent recruitment of upland and intertidal vegetation, and restoration projects have naturalized some shorelines in this urban setting. We determined the species composition and relative abundance of fishes and crabs in shallow shoreline habitats in constructed embayments of UNYH with seine sampling to determine the potential for restoring similar isolated shallow water sites as functional habitats. Twenty‐seven identified species of fishes and crabs, including seasonally transient and resident marsh species, were represented in samples dominated by Menidia menidia, but marsh resident and coastal ocean species were also periodically abundant. Differences in assemblage structure among the sampled embayments as measured by principal components analysis were weak despite some differences in the slope and colonization of vegetation along shorelines. The mere presence of shallow shorelines was sufficient to recruit numerous species. Assemblage differences relative to a nearby relatively unaltered estuary revealed a lack of southern, warm affiliated species reflecting a natural clinal gradient. Marsh resident species dominated in UNYH, but not as strongly as at the reference estuary. Together with a previously published evaluation of life cycle connectivity for several sentinel species, this study shows that even small, isolated projects seeking to restore shallow shorelines add value to the estuarine landscape and are worth pursuing.

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Context is more important than habitat type in determining use by juvenile fish

Cited by 69 publications

References 67 publications

Tethering mobile aquatic organisms to measure predation: A renewed call for caution

Tethering mobile aquatic organisms to measure predation: A renewed call for caution

Hypoxia in mangroves: occurrence and impact on valuable tropical fish habitat

Shoreline infrastructure degradation and increasing littoral naturalization accommodates juvenile fish and crab assemblages in heavily urbanized Upper New York Harbor

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