Video2.mp4

<p>Deep-sea fish species are targeted globally by bottom trawling. The species captured are often characterized by longevity, low fecundity and slow growth making them vulnerable to overfishing. In addition, bottom trawling is known to remove vast amounts of non-target species, including habitat forming deep-sea corals and sponges. Therefore, bottom trawling poses a serious risk to deep-sea ecosystems, but the true extent of deep-sea fishery catches through history remains unknown. Here, we present catches for global bottom trawling fisheries between years 1950–2015. This study gives new insight into the history of bottom trawled deep-sea fisheries through its use of FAO capture data combined with reconstructed catch data provided by the Sea Around Us- project, which are the only records containing bycatches, discards and unreported landings for deep-sea species. We illustrate the trends and shifts of the fishing nations and discuss the life-history and catch patterns of the most prominent target species over this time period. Our results show that the landings from deep-sea fisheries are miniscule, contributing less than 0.5% to global fisheries landings. The fisheries were found to be overall under-reported by as much as 42%, leading to the removal of an estimated 25 million tons of deep-sea fish. The highest catches were of Greenland halibut in the NE Atlantic, Longfin codling from the NW Pacific and Grenadiers and Orange roughy from the SW Pacific. The results also show a diversification through the years in the species caught and reported. This historical perspective reveals that the extent and amount of deep-sea fish removed from the deep ocean exceeds previous estimates. This has significant implications for management, conservation and policy, as the economic importance of global bottom trawling is trivial, but the environmental damage imposed by this practice, is not.</p

Video1.MP4

<p>Deep-sea fish species are targeted globally by bottom trawling. The species captured are often characterized by longevity, low fecundity and slow growth making them vulnerable to overfishing. In addition, bottom trawling is known to remove vast amounts of non-target species, including habitat forming deep-sea corals and sponges. Therefore, bottom trawling poses a serious risk to deep-sea ecosystems, but the true extent of deep-sea fishery catches through history remains unknown. Here, we present catches for global bottom trawling fisheries between years 1950–2015. This study gives new insight into the history of bottom trawled deep-sea fisheries through its use of FAO capture data combined with reconstructed catch data provided by the Sea Around Us- project, which are the only records containing bycatches, discards and unreported landings for deep-sea species. We illustrate the trends and shifts of the fishing nations and discuss the life-history and catch patterns of the most prominent target species over this time period. Our results show that the landings from deep-sea fisheries are miniscule, contributing less than 0.5% to global fisheries landings. The fisheries were found to be overall under-reported by as much as 42%, leading to the removal of an estimated 25 million tons of deep-sea fish. The highest catches were of Greenland halibut in the NE Atlantic, Longfin codling from the NW Pacific and Grenadiers and Orange roughy from the SW Pacific. The results also show a diversification through the years in the species caught and reported. This historical perspective reveals that the extent and amount of deep-sea fish removed from the deep ocean exceeds previous estimates. This has significant implications for management, conservation and policy, as the economic importance of global bottom trawling is trivial, but the environmental damage imposed by this practice, is not.</p

Table1.XLSX

<p>Deep-sea fish species are targeted globally by bottom trawling. The species captured are often characterized by longevity, low fecundity and slow growth making them vulnerable to overfishing. In addition, bottom trawling is known to remove vast amounts of non-target species, including habitat forming deep-sea corals and sponges. Therefore, bottom trawling poses a serious risk to deep-sea ecosystems, but the true extent of deep-sea fishery catches through history remains unknown. Here, we present catches for global bottom trawling fisheries between years 1950–2015. This study gives new insight into the history of bottom trawled deep-sea fisheries through its use of FAO capture data combined with reconstructed catch data provided by the Sea Around Us- project, which are the only records containing bycatches, discards and unreported landings for deep-sea species. We illustrate the trends and shifts of the fishing nations and discuss the life-history and catch patterns of the most prominent target species over this time period. Our results show that the landings from deep-sea fisheries are miniscule, contributing less than 0.5% to global fisheries landings. The fisheries were found to be overall under-reported by as much as 42%, leading to the removal of an estimated 25 million tons of deep-sea fish. The highest catches were of Greenland halibut in the NE Atlantic, Longfin codling from the NW Pacific and Grenadiers and Orange roughy from the SW Pacific. The results also show a diversification through the years in the species caught and reported. This historical perspective reveals that the extent and amount of deep-sea fish removed from the deep ocean exceeds previous estimates. This has significant implications for management, conservation and policy, as the economic importance of global bottom trawling is trivial, but the environmental damage imposed by this practice, is not.</p

Depth distribution of the 14 Chrysogorgiidae genera based on 959 depth records.

<p>Depth records are summarized as box-and-whisker plots displaying the minimum, first quartile, median (bolded line), third quartile, and maximum values. Statistical outliers (>1.5x the inter-quartile range) are presented as open circles. Genera are sorted by increasing median depth (in meters, log scale) and sample size (number of biogeographic records) is provided on the top side of the plot. The 200 m isobath is represented (dashed line) as an arbitrary limit between deep and shallow waters.</p

Maximum likelihood reconstruction of the suborder Calcaxonia (rooted to <i>Funiculina</i>, a sea pen) based on concatenated sequences of the 5′ end of <i>mtMutS</i>, <i>cox1</i> and 18S (64 taxa, 2924 bp; GTR+I+G model; 500 bootstrap replicates).

<p>All five families of the Calcaxonia are represented. Node support values from the ML analysis (>70%, bold) are indicated under each node, and node support values from the Bayesian analysis (>0.90) are above each node. Chrysogorgiidae taxa are either color coded (MCC) or have bolded branches (nonMCC).</p

Depth range of 89 species (541 records) from the MCC (left) and resulting species diversity gradient (right).

<p>On the left panel, each segment links the maximum and minimum collection depths for a particular species. Species within genera are sorted by increasing median depth (m). The 200 m isobath is represented as a dashed line. Ra: <i>Radicipes</i>, I: <i>Iridogorgia</i>, R: <i>Rhodaniridogorgia</i>, P: <i>Pseudochrysogorgia</i>, M: <i>Metallogorgia</i>.</p

Bathymetric range and biodiversity within the monophyletic, deep-sea Chrysogorgiidae (MCC).

<p>Diversity: morphology estimate based on number of nominal species; genetic estimate based on number of <i>mtMutS</i> haplotypes. N: sample size (morphology: number of biogeographic records, and minimum number of colonies in parentheses), Atl: Atlantic Ocean, Ind: Indian Ocean, Pac: Pacific Ocean, Ant: Antarctic Ocean. Some depth estimates are based on depth ranges from trawling stations, in which case minimum and maximum depths were averaged (see notes in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0038357#s4" target="_blank">Material and Methods</a> section).</p

PCR primers used in the present study to amplify targeted gene regions.

<p>Predicted fragment sizes (approximate, in bp) and PCR cycle profiles (temperature in °C: time in seconds) are given for the most commonly used primer pairs. Primer combinations are listed in the product size column, prior to the predicted fragment size, using the primer numbers defined in the first column. (mod.: modified from). Between 30 and 45 cycles were used for PCR.</p

Length and information content of <i>mtMutS</i>, <i>cox1</i> and 18S alignments, alone and concatenated.

<p>Alignments 1–8 were used in phylogenetic analyses. Alignments 8–12 were used to compare levels of variation and information content, based on data from 42 individuals. Gblocks: alignment shortened using Gblocks. N. nt: alignment length in nucleotides. Nt. min-max: shortest and longest sequences (de-gapped). N. var and N. pars: number of variable and parsimony-informative sites (and percentage of total alignment length). Model (AIC) and Model (BIC): model of evolution that best described the data, based on jModelTest runs.</p

Bayesian 50% majority rule consensus trees based on different markers (<i>mtMutS</i>, <i>cox1</i> and 18S) and marker combinations.

<p>For <i>mtMutS</i>, the effect of indels on phylogeny inference was tested by removing them with Gblocks. Chrysogorgiidae taxa are either color coded (MCC) or have bolded branches (nonMCC).The MCC clade is evidenced by a gray circle. All trees are rooted to the Pennatulacea, except trees using the entire <i>mtMutS</i> gene (rooted to the Ellisellidae). For sake of clarity, tip labels and node support values were removed, but can be consulted on <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0038357#pone.0038357.s001" target="_blank">Figure S1</a>.</p