Predator and scavenger aggregation to discarded by-catch from dredge fisheries: importance of damage level

Jenkins, Stuart R.; Mullen, Carrie; Brand, A. R.

doi:10.1016/j.seares.2003.05.002

Cited by 46 publications

(34 citation statements)

References 24 publications

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“…In addition, even scallops that encounter the dredges without damage to their shells suffer an impaired swimming escape response . These damaged and/or stressed scallops are known to be more vulnerable and attractive to predators than undisturbed individuals (Jenkins et al 2004).…”

Section: Discussionmentioning

confidence: 99%

Benefits of closed area protection for a population of scallops

Stewart¹,

Vause²,

Mosley³

et al. 2005

Mar. Ecol. Prog. Ser.

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Despite the current interest in using closed areas for fisheries management, few studies have actually examined the benefits for invertebrate fisheries such as scallops. This study details the dynamics of a population of great scallops Pecten maximus (L.), within a closed area and an adjacent fished area off the Isle of Man, over a 14 yr period (1989 to 2003). Scallop densities were very low in both areas when the closed area was set up, but increased at an accelerated rate over time within the closed area. Scallop densities also increased on the adjacent fishing ground, but not to the same extent. Consequently, the density of scallops above the minimum legal landing size (110 mm SL) was more than 7 times higher in the closed area than in the fished area by 2003. There was also a shift towards much older and larger scallops in the closed area and, correspondingly, lower estimates of total mortality. Experimental dredging of 2 plots within the closed area confirmed that fishing drove these differences in population dynamics and structure. These patterns of scallop density, age and size structure resulted in the exploitable biomass (adductor muscle and gonad) of scallops being nearly 11 times higher in the closed area than in the fished area by 2003, and the reproductive biomass was 12.5 times higher. This is significant for fisheries management because the build up of high densities of large P. maximus individuals enhanced local reproductive potential and therefore the likelihood of export of larvae to the surrounding fishing grounds. Along with these direct benefits of closed area protection, juvenile scallops had higher survival and individual growth rates in the closed area, apparently in response to reduced fishing disturbance. Although juvenile scallops are not subject to direct removal by fishing, protection during this critical phase therefore appeared to assist the recovery of the closed area population. In summary, this study joins a growing number indicating that the use of closed areas offers a range of benefits over more traditional methods of managing fisheries. Fisheries for relatively sedentary and long-lived species such as P. maximus appear to be particularly suitable for this type of management.

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Section: Discussionmentioning

confidence: 99%

Benefits of closed area protection for a population of scallops

Stewart¹,

Vause²,

Mosley³

et al. 2005

Mar. Ecol. Prog. Ser.

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“…Alves et al (2003) highlighted that after dredging activity abundance, number of taxa, evenness, diversity and biomass showed a decrease in Portugal clam dredging trials. Gaspar et al (2003) announced that the abundance of hermit crabs may not be regarded as a universal monitoring tool in identifying fishing areas because of the aggregation of scavengers, such as hermit crabs, in fished areas can last from a few minutes (Gaspar et al, 2003) to a few days (Jenkins et al, 2004); in this study D. pugilator, a scavenger, was a good discriminator for G1 (in SIMPER).…”

Section: Discussionmentioning

confidence: 67%

Untitled

Dalgıç¹,

Ceylan²

2012

Turk. J. Fish. Aquat. Sci.

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Seasonal discards and by-catch of hydraulic dredges targeting striped venus clams, Chamelea gallina, from the Black Sea coasts of Turkey were determined. Data presented in this study were collected by researchers aboard between September 2009 and April 2010. Results indicated that discards were 36% of the landed product, of which 19% was composed of undersized (<17 mm) clams. During the study, a total of 38 species were identified and the hermit crab (Diogenes pugilator) and the gastropod Rapana venosa were the two main species captured as discard from all sampling stations in every season. Species diversity and evenness index values, of winter and spring hauls were significantly different from autumn ones.Keywords: Chamelea gallina, striped venus clam, discards, hydraulic dredge, Black Sea. Karadeniz'de Beyaz Kum Midyesi (Chamelea gallina) Avcılığında Mevsimsel Iskarta ve Hedef Dışı Av ÖzetKaradeniz'in Türkiye kıyılarında beyaz kum midyesi, Chamelea gallina, avcılığı yapan hidrolik direç donanımlı teknelerin mevsimsel ıskarta ve hedef dışı av miktarları tespit edilmiştir. Bu çalışmada kullanılan veriler araştırmacılar tarafından Eylül 2009 ve Nisan 2010 tarihleri arasında ticari av teknelerinden elde edilmiştir. Elde edilen sonuçlara göre Karadeniz'de hidrolik direçlerin ürettikleri ıskarta miktarları karaya çıkarılan ürünün %36'sına tekabül etmektedir ve bunun yaklaşık %19'u asgari av boyunun (<17 mm) altındaki kum midyesi bireylerinden oluşmaktadır. Çalışma süresince toplam 38 tür tespit edilmiştir ve keşiş yengeci (Diogenes pugilator) ile deniz salyangozu Rapana venosa tüm istasyonlarda her mevsim elde edilen iki ana ıskarta türdür. Kışın ve ilkbaharda yapılan çekimler, tür çeşitliliği ve homojenlik değerleri açısından sonbaharda yapılanlara göre önemli derecede farklıdır.Anahtar Kelimeler: Chamelea gallina, beyaz kum midyesi, ıskarta, hidrolik direç, Karadeniz.

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“…This confirms our first hypothesis that the attracted scavengers quickly remove the damaged benthos. The process resembles that described after simulated benthic fisheries damage to scallops in the north Irish Sea (Jenkins et al, 2004): while baited, heavily damaged scallops were eaten within 24 h, lightly damaged individuals were inaccessible until large crustaceans (Cancer pagurus) made the body tissue available, causing protracted aggregation and feeding for up to 96 h. Our dead organisms were shell-less, but the tunics of ascidians, for example, probably also delayed access by less powerful hermit crabs or small gobiids, explaining the presence of scavengers at the end of the experiments (67.5 and 71.5 h).…”

Section: Short-term Post-anoxia Scavengingmentioning

confidence: 60%

Short-term post-mortality scavenging and longer term recovery after anoxia in the northern Adriatic Sea

et al. 2013

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Abstract. The northern Adriatic Sea is one of nearly 500 areas worldwide suffering widespread mortalities due to anoxia. The present study documents post-anoxia macrofauna dynamics after experimentally inducing small-scale anoxia in 24 m depth (2 plots, each 50 cm × 50 cm). Timelapse camera deployments examined short-term scavenging of the moribund and dead organisms (multi-species clumps consisting of sponges and ascidians) over two 3-day periods (August 2009: 71.5 h, September 2009: 67.5 h). Longer term recovery (days to 2 yr) in the same two plots was examined with an independent photo series. Scavengers arrived quickly and in a distinct sequence: demersal (Gobius niger, Serranus hepatus) and benthopelagic fishes (Diplodus vulgaris, Pagellus erythrinus), followed by hermit crabs (Paguristes eremita, showing a clear day/night rhythm in presence) and gastropods (Hexaplex trunculus). This sequence is attributed to the relative speeds and densities of the organisms. The sessile fauna was largely removed or consumed within seven (August plot) and 13 (September plot) days after anoxia, confirming our first hypothesis that decaying organisms are quickly utilised. The scavengers remained in dense aggregations (e.g. up to 33 P. eremita individuals at one time) as long as dead organisms were available. No recovery of sessile macroepibenthos macroepibenthos occurred in the experimental plots one and two years after anoxia, undermining our second hypothesis that small denuded areas are more rapidly recolonised. This study underlines the sensitivity of this soft-bottom community and supports calls for reducing additional anthropogenic disturbances such as fishing practices that further impede recolonisation and threaten benthic community structure and function over the long term.

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Predator and scavenger aggregation to discarded by-catch from dredge fisheries: importance of damage level

Cited by 46 publications

References 24 publications

Benefits of closed area protection for a population of scallops

Benefits of closed area protection for a population of scallops

Untitled

Short-term post-mortality scavenging and longer term recovery after anoxia in the northern Adriatic Sea

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