The influence of increased line‐fishing mortality on the sex ratio and age of sex reversal of the venus tusk fish

Platten, John.; Tibbetts, Ian R.; Sheaves, Marcus

doi:10.1111/j.1095-8649.2002.tb00281.x

Cited by 39 publications

(29 citation statements)

References 24 publications

(34 reference statements)

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“…Sex allocation theory for sequential hermaphrodites (Warner 1975;Charnov 1982) predicts that size (age) at sex change should be reduced in populations where large adults have high mortality rates in order to compensate for potential impacts on breeding sex ratio. Previous studies have shown that several fish and invertebrate species (two temperate shrimp and one limpet) that are under harvesting pressure do indeed change sex at smaller sizes, supporting the theoretical prediction (Charnov 1981;Cowen 1990;Hannah and Jones 1991;Buxton 1993;Charnov and Hannah 2002;Platten et al 2002;Hawkins and Roberts 2004;Hamilton et al 2007;Götz et al 2008;Rivera-Ingraham et al 2011).…”

Section: Introductionsupporting

confidence: 67%

Anthropogenic Harvesting Pressure and Changes in Life History: Insights from a Rocky Intertidal Limpet

Fenberg

Roy²

2012

The American Naturalist

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The importance of large breeding individuals for maintaining the health of marine fish and invertebrate populations has long been recognized. Unfortunately, decades of human harvesting that preferentially remove larger individuals have led to drastic reductions in body sizes of many of these species. Such size-selective harvesting is particularly worrisome for sequentially hermaphroditic species where the larger size classes are composed primarily of one sex. Whether these species can maintain stable sex ratios under sustained harvesting pressure depends on the level of plasticity of their life-history traits. Here, we show that populations of a marine limpet (Lottia gigantea) can adjust a fundamental aspect of their life history (the timing of sex change) when subjected to size-selective harvesting. As predicted by theoretical models, individuals from harvested populations change sex at smaller sizes and grow at slower rates compared to individuals from protected populations. In addition, the relative size at which the change from male to female occurs remains constant (∼0.75; size at sex change/maximum size) across populations, regardless of harvesting pressure. Our results show that populationlevel demographic and life-history data, in conjunction with existing theory, can be sufficient to predict the responses of sequential hermaphrodites to harvesting pressure. Furthermore, they suggest such species can potentially adapt to size-selective harvesting.

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Section: Introductionsupporting

confidence: 67%

Anthropogenic Harvesting Pressure and Changes in Life History: Insights from a Rocky Intertidal Limpet

Fenberg

Roy²

2012

The American Naturalist

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“…Changing sex earlier in life (e.g. at a smaller size) would be a possible population response for hermaphroditic fishes experiencing sex related fishing pressure (Platten et al, 2002). However, again such internal population processes are not fast, and will not likely prevent drastic population declines promoted by intense fishing.…”

Section: Discussionmentioning

confidence: 99%

Local ecological knowledge on the goliath grouper epinephelus itajara (teleostei: serranidae) in southern Brazil

Gerhardinger¹,

Marenzi

Bertoncini³

et al. 2006

Neotrop. ichthyol.

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The goliath grouper Epinephelus itajara is a large sized (> 400 kg) and critically endangered marine fish, which is protected in many countries, including Brazil. Through the application of semi-structured interviews, we investigated the local ecological knowledge of seven fishermen specialist on catching E. itajara from the Babitonga bay, Santa Catarina, Brazil. Local long-line fisheries for E. itajara seemed to be a disappearing tradition in the studied site, with a detailed inherent local ecological knowledge system, which is also being lost. Our study also showed that fishermen engaged in recent fisheries, such as spear-fishing, can also possess a detailed local ecological knowledge system. Through the analysis of fishermen local ecological knowledge, several aspects of E. itajara life history were registered. This species is found in the inner and outer Babitonga bay, from saline waters to areas with a large input of freshwater, and inhabits submerged wooden substrates and artificial reefs such as shipwrecks, mooring pillars and cargo containers. It is known to spawn in December and subsequent summer months in the studied area. Spawning aggregations are usually seen in December (during full moon), being also eventually observed in January and February by our informants. While lobsters, spadefishes and octopuses seem to constitute the most important food items of inner bay E. itajara, outer bay individuals may feed on catfishes, crustaceans and other fish species. The goliath grouper is regarded as pacific and curious fish, but frequently display agonistic behavior in the presence of divers. Based on the perception of well experienced spear fishermen, we hypothesize that E. itajara undertakes seasonal migrations from the inner to the outer bay during summer, and that the studied population is suffering from growth over-fishing. Our data provides a practical evidence of how joining scientific and local ecological knowledge will likely benefit E. itajara local conservation and management practices by adding important new biological data into the decision-making process.O mero Epinephelus itajara é uma espécie de peixe marinho de grandes proporções (>400 kg) e criticamente ameaçado, protegido em muitos países, incluindo o Brasil. Através da aplicação de entrevistas semi-estruturadas, investigamos o conhecimento ecológico local de pescadores de espinhel e pesca subaquática, especialistas na captura de E. itajara na baía Babitonga, Santa Catarina, Brasil. A pescaria de espinhel direcionada à E. itajara parece ser uma tradição em desaparecimento, com um detalhado sistema de conhecimento ecológico local que está também sendo perdido com o tempo. Nosso estudo mostra que pescadores envolvidos em pescarias recentes, como a pesca subaquática, podem também possuir detalhado sistema de conhecimento ecológico local. Através da análise e integração do conhecimento ecológico local dos informantes, diversos aspectos da história de vida de E. itajara foram registrados. Esta espécie é encontrada na porção interna e externa da ...

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“…However, opportunities for observing predation effects continue to diminish; few truly natural and wild ecosystems remain today, including coral reefs and the fish assemblages that conspicuously characterize them. Responses of reef fish prey to predation include, but are not limited to, reductions in abundance and shifts in size composition to smaller body sizes (Connell 1998), changes in the sheltering behavior of prey (Sackley & Kaufman 1996), alterations of interactions among prey species (Almany 2003), increased survivorship of unpreferred prey (Webster & Almany 2002), and shifts to smaller sizes at sexual maturation and sex change (Platten et al 2002, Hawkins & Roberts 2004a, DeMartini et al 2005.…”

Section: Introductionmentioning

confidence: 99%

Differences in fish-assemblage structure between fished and unfished atolls in the northern Line Islands, central Pacific

DeMartini¹,

Friedlander²,

Sandin³

et al. 2008

Mar. Ecol. Prog. Ser.

187

210

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We describe the abundance, biomass, size composition, and trophic structure of fish assemblages of shallow (10 m depth) fore reef habitats at 2 US Pacific atolls (Kingman, Palmyra) and 2 Kiribati-owned atolls (Tabuaeran, Kiritimati) in the northern Line Islands. Our characterization spans several coincident gradients (in human habitation and exploitation, latitude, and nutrient upwelling) from uninhabited, presently unfished, and oligotrophic Kingman to relatively densely populated, fished, and equatorially upwelled Kiritimati. Major findings are most consistent with direct effects of extraction on large-bodied predators and indirect effects on lower-level assemblage structure. Fish assemblages at Palmyra and especially Kingman atolls were characterized by high total standing biomass, large average body sizes, a preponderance of apex predators and other piscivorous fishes in an inverted biomass pyramid, few and small planktivorous fishes, and herbivores dominated by non-territorial species. Median body sizes at color change from initial to terminal phase (an index of sex change in parrotfishes) were also small for 4 species of parrotfish at Kingman and Palmyra. Fish assemblages at Tabuaeran and especially Kiritimati atolls had starkly contrasting characteristics: piscivorous and other fisheries-targeted fishes were depauperate, lower-trophic levels dominated fish biomass, planktivorous fishes were larger-bodied and more numerous, territorial herbivores were better represented, and size at maturation in parrotfishes was proportionately larger. Our results show the effects that even modest fishing effort can have on assemblage structure and indicate the importance of reefs like Kingman as increasingly rare relicts of natural coral reefs, providing insights into the natural structure and function of these ecosystems.

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The influence of increased line‐fishing mortality on the sex ratio and age of sex reversal of the venus tusk fish

Cited by 39 publications

References 24 publications

Anthropogenic Harvesting Pressure and Changes in Life History: Insights from a Rocky Intertidal Limpet

Anthropogenic Harvesting Pressure and Changes in Life History: Insights from a Rocky Intertidal Limpet

Local ecological knowledge on the goliath grouper epinephelus itajara (teleostei: serranidae) in southern Brazil

Differences in fish-assemblage structure between fished and unfished atolls in the northern Line Islands, central Pacific

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