(1 - 3 of 3)
- Natural History Observations of Hawaiian Garden Eels, Gorgasia hawaiiensis (Congridae: Heterocongrinae), from the Island of Hawai'i, Natural History Observations of Hawaiian Garden Eels
- Garden eels occur worldwide in the tropics, but little is known about their biology and ecology. We studied Hawaiian garden eel (Gorgasia hawaiiensis) colonies near Kawaihae, Hawai'i, to investigate multiple aspects of basic biology of this species. Colonies of G. hawaiiensis occurred at depths from 16 to 36 m in soft-bottom habitat adjacent to rocky reefs. Highest burrow densities (up to 40 eels m-2) were in shallower water, and large (~10 mm diameter) burrows were more abundant, less dense, and commonly found in pairs in deeper water. Eels emerged around sunrise and withdrew and covered burrow entrances around sunset. Age was estimated from annual rings in sectioned otoliths (n = 17) and modeled to suggest fast growth to a maximum size of ~600 mm total length and a maximum age of 6 yr. Prey size and eel anatomy suggest that these fish feed by ingesting planktonic prey and processing them in the esophagus. The most common food items were small (<0.5 mm) demersal harpacticoid, cyclopoid, and calanoid copepods and unidentified fish eggs. These and other observations indicate that G. hawaiiensis is abundant, has a high population turnover rate, and may enrich sandy-bottom habitat within their beds by facilitating energy flow from the water column to the benthos. © 2017 by University of Hawai'i Press., Export Date: 17 April 2017, Article
- Donham, Foster, Rice, Cailliet, Yoklavich, Hamilton
- Historical ecology and the conservation of large, hermaphroditic fishes in Pacific Coast kelp forest ecosystems
- The intensive commercial exploitation of California sheephead (Semicossyphus pulcher) has become a complex, multimillion-dollar industry. The fishery is of concern because of high harvest levels and potential indirect impacts of sheephead removals on the structure and function of kelp forest ecosystems. California sheephead are protogynous hermaphrodites that, as predators of sea urchins and other invertebrates, are critical components of kelp forest ecosystems in the northeast Pacific. Overfishing can trigger trophic cascades and widespread ecological dysfunction when other urchin predators are also lost from the system. Little is known about the ecology and abundance of sheephead before commercial exploitation. Lack of a historical perspective creates a gap for evaluating fisheries management measures and marine reserves that seek to rebuild sheephead populations to historical baseline conditions. We use population abundance and size structure data from the zooarchaeological record, in concert with isotopic data, to evaluate the long-term health and viability of sheephead fisheries in southern California. Our results indicate that the importance of sheephead to the diet of native Chumash people varied spatially across the Channel Islands, reflecting modern biogeographic patterns. Comparing ancient (~10,000 calibrated years before the present to 1825 CE) and modern samples, we observed variability and significant declines in the relative abundance of sheephead, reductions in size frequency distributions, and shifts in the dietary niche between ancient and modern collections. These results highlight how size-selective fishing can alter the ecological role of key predators and how zooarchaeological data can inform fisheries management by establishing historical baselines that aid future conservation.
- Braje, Rick, Szpak, Newsome, McCain, Elliott Smith, Glassow, Hamilton
- From a sea of phenotypic traits, fast reaction and boldness emerge as the most influential to survival in marine fish
- Predation is arguably the most consequential of ecological interactions in determining fitness and thus natural selection; prey that do not escape a predator encounter become dinner and can no longer pass their genes on to the next generation. For organisms with complex life histories (e.g. plants, insects, amphibians, marine fish, invertebrates and algae; Wilbur, 1980), processes occurring during transitions between life stages are particularly important for subsequent survival and reproduction (e.g. Berven, 1990; Johnson, Grorud‐Colvert, Sponaugle, & Semmens, 2014; Pechenik, 2006). Mortality is intense at these vulnerable developmental stages (Almany & Webster, 2006; Hjort, 1914), especially when those life‐history transitions involve a habitat shift (i.e. pelagic larva to benthic‐associated juvenile for marine species) where individuals are naïve about new predators and other risks. In marine systems, early results showed that bigger, faster growing, or better‐conditioned individuals were more likely to survive the larval‐juvenile transition (Hamilton, Regetz, & Warner, 2008; Hoey & McCormick, 2004; Searcy & Sponaugle, 2001; Vigliola & Meekan, 2002). Understanding which individuals survive periods of selective mortality, from birth to reproduction, remains fundamental to our understanding of both demographic and evolutionary processes.