Author Topic: Science corner: latest fish & fisheries research (Read 199808 times)

John F · « **Reply #100 on:** January 19, 2016, 06:28:33 PM »

How sailfish use their bills to capture schooling prey

* The istiophorid family of billfishes is characterized by an extended rostrum or ‘bill’.

* While various functions (e.g. foraging and hydrodynamic benefits) have been proposed for this structure, until now no study has directly investigated the mechanisms by which billfishes use their rostrum to feed on prey.

* The first unequivocal evidence of how the bill is used by Atlantic sailfish (Istiophorus albicans) to attack schooling sardines in the open ocean is presented.

* Using high-speed video-analysis, it is shown that (i) sailfish manage to insert their bill into sardine schools without eliciting an evasive response and (ii) subsequently use their bill to either tap on individual prey targets or to slash through the school with powerful lateral motions characterized by one of the highest accelerations ever recorded in an aquatic vertebrate.

* The results demonstrate that the combination of stealth and rapid motion make the sailfish bill an extremely effective feeding adaptation for capturing schooling prey.

Sailfish Hunting Sardines (Normal & Slow Motion Attacks)

PDF available.

Reference:
Domenici, P. et al. (2014). How sailfish use their bills to capture schooling prey. Proceedings of the Royal Society B, 281: 20140444.

REEFMAN · « **Reply #101 on:** January 20, 2016, 07:26:02 AM »

Awesome footage!

John F · « **Reply #102 on:** January 26, 2016, 10:34:28 AM »

The dilema of derelict gear

* Every year, millions of pots and traps are lost in crustacean fisheries around the world. Derelict fishing gear has been found to produce several harmful environmental and ecological effects, however socioeconomic consequences have been investigated less frequently.

* The economic effects of a substantial derelict pot removal program in the largest estuary of the United States, the Chesapeake Bay were analyzed.

* By combining spatially resolved data on derelict pot removals with commercial blue crab (Callinectes sapidus) harvests and effort, it is shown that removing 34,408 derelict pots led to significant gains in gear efficiency and an additional 13,504 MT in harvest valued at US $21.3 million—a 27% increase above that which would have occurred without removals.

* Model results are extended to a global analysis where it is seen that US $831 million in landings could be recovered annually by removing less than 10% of the derelict pots and traps from major crustacean fisheries.

* An unfortunate common pool externality, the degradation of marine environments is detrimental not only to marine organisms and biota, but also to those individuals and communities whose livelihoods and culture depend on profitable and sustainable marine resource use.

PDF available.

Reference:
Scheld, A. M., D. M. Bilkovic & K. J. Havens (2016). The dilemma of derelict gear. Scientific Reports, 6: 19671.

L Hooker · « **Reply #103 on:** January 26, 2016, 02:49:13 PM »

Great footage John explains the bill rash we so like to see on our lures

icstuff · « **Reply #104 on:** February 22, 2016, 01:54:28 PM »

DNA evidence shows that hatcheries cause substantial, rapid genetic changes

The research, published today in Nature Communications, found that after one generation of hatchery culture, the offspring of wild fish and first-generation hatchery fish differed in the activity of more than 700 genes.

A single generation of adaptation to the hatchery resulted in observable changes at the DNA level that were passed on to offspring, scientists reported.

This research was conducted at Oregon State University in collaboration with the Oregon Department of Fisheries and Wildlife.
Scientists say the findings essentially close the case on whether or not wild and hatchery fish can be genetically different.
Source:
http://www.eurekalert.org/pub_releases/2016-02/osu-des021216.php

John F · « **Reply #105 on:** February 24, 2016, 09:33:14 AM »

Challenges of estimating post-release mortality of istiophorid billfishes caught in the recreational fishery: A review

* Istiophorid billfishes are targeted in recreational fisheries throughout the tropical and subtropical waters of the world's oceans.

* Over the past thirty years, changes in management regulations and increased angler conservation awareness have resulted in an increasing proportion of the billfish catch being released alive, and in many areas the fishery is principally catch-and-release.

* However, the fate of released fish, and thus the fishing mortality associated with the recreational fishery, is not well understood.

* Some insights into post-release mortality of billfishes caught in the recreational fishery have been gained from analyses of conventional tag data, hooking location information, and acoustic tracking data.

* Over the past 10 years pop-up satellite archival tags (PSATs) have been used to specifically estimate post-release mortality for a limited number billfish species.

* Extrapolation of the results of these limited studies throughout the various recreational billfish fisheries is not prudent due to potential influences of different species, areas, seasons, fishing styles, and hook types.

* The current high cost of PSATs presents a significant obstacle to evaluating the effect of these variables on rates of post-release survival. Nonetheless, the results of the few studies to date have had an important impact on fisheries management and the behavior of recreational anglers.

PDF available.

Reference:
Graves, J. E. & A. Z. Horodysky (2015). Challenges of estimating post-release mortality of istiophorid billfishes caught in the recreational fishery: A review. Fisheries Research, 166: 163-168.

John F · « **Reply #106 on:** February 24, 2016, 09:45:44 AM »

Postrelease mortality in istiophorid billfish

* Meta-analysis (inverse-variance, random-effects model) involving 46 studies was used to estimate the effect size of postrelease mortality (F_r) in six istiophorid billfish species (black marlin (Istiompax indica), blue marlin (Makaira nigricans), longbill spearfish (Tetrapturus pfluegeri), sailfish (Istiophorus platypterus), striped marlin (Kajikia audax), and white marlin (Kajikia albida) following release from recreational, longline, and harpoon fishing gears.

* The studies involved 400 reporting pop-up satellite archival tags and 64 reporting acoustic (ultrasonic) tags.

* Despite fish being captured, tagged, and released under widely disparate conditions, locations, and gear types, F_r was homogeneous among species.

* Variability in F_r was principally due to random sampling error within studies with no evident patterns.

* Fifteen studies (33% of tags) indicated no mortality, and the overall summary effect size for F_r was 13.5% (95% CI: 10.3%–17.6%).

* Since the random-effects model decomposed to a fixed-effect model when the between-studies variance T² = 0.00, results were confirmed using exact nonparametric inferential tests and sensitivity analyses.

* The results support earlier findings in the Atlantic and substantiate the majority of istiophorid billfish survive when released from recreational and longline fishing gear, clearly implying catch-and-release as a viable management option that permits fishing activity while protecting parental biomass and the fishery.

PDF available.

Reference:
Musyl, M. K., C. D. Moyes, R. W. Brill, B. L. Mourato, A. West, L. M. McNaughton, W.-C. Chiang & C.-L. Sun (2015). Postrelease mortality in istiophorid billfish. Canadian Journal of Fisheries and Aquatic Sciences, 72: 538-556.

REEFMAN · « **Reply #107 on:** February 24, 2016, 10:16:07 AM »

Quote from: John F on February 24, 2016, 09:45:44 AM

Postrelease mortality in istiophorid billfish

* The results support earlier findings in the Atlantic and substantiate the majority of istiophorid billfish survive when released from recreational and longline fishing gear, clearly implying catch-and-release as a viable management option that permits fishing activity while protecting parental biomass and the fishery.

That's brilliant news! Finally we can put an end to the nonsense and speculation.

Marthin · « **Reply #108 on:** February 24, 2016, 10:31:06 AM »

To be honest ive never understood the discussion... If released and floating away belly up and a 0.005% chance of survival, it's still 100% higher survival possibility than on the deck. The amount of fish caught with entire gill plates or jaws missing should have been enough evidence years ago.

FishStyx · « **Reply #109 on:** February 24, 2016, 10:34:51 AM »

Awesome news indeed.

John F · « **Reply #110 on:** April 28, 2016, 01:23:36 PM »

Growth rate of speckled snapper Lutjanus rivulatus (Teleostei: Lutjanidae) based on tag-recapture data from the iSimangaliso Wetland Park, South Africa

* The growth rate of speckled snapper Lutjanus rivulatus was investigated using data from a long-term tag-recapture study conducted in the St Lucia Marine Reserve within the iSimangaliso Wetland Park, a World Heritage Site in northern KwaZulu-Natal, South Africa;

* A total of 1 429 L. rivulatus were tagged and 453 (31.7%) individual fish were recaptured one or more times;

* Growth rates were modelled from the tag-recapture data using a maximum-likelihood approach;

* It is shown that L. rivulatus is a slow-growing species with L∞ = 918 mm FL, K = 0.06 and phi-prime (Ø, the
growth index) = 2.69;

* The effects of deep-hooking and multiple captures were tested and this revealed that there was no significant impact on the growth of L. rivulatus;

* The growth index was lower than that recorded in many other similar congeneric species;

* Slow growth, coupled with high levels of residency and site fidelity, suggest that this species is vulnerable to exploitation and that a precautionary approach towards future management is appropriate.

PDF available.

Reference:

Mann, B. Q., B. Lee & P. D. Cowley (2016). Growth rate of speckled snapper Lutjanus rivulatus (Teleostei: Lutjanidae) based on tag-recapture data from the iSimangaliso Wetland Park, South Africa. African Journal of Marine Science, 38: 111-118.

REEFMAN · « **Reply #111 on:** April 28, 2016, 05:05:36 PM »

Over 30% recapture rate is quite amazing. Just shows how extremely territorial they are.
Release your Speckleds!

John F · « **Reply #112 on:** April 28, 2016, 05:34:16 PM »

Knew I'd get your attention Reefz!

REEFMAN · « **Reply #113 on:** April 29, 2016, 08:37:57 AM »

Very slow growing... So how old would this one be?!

John F · « **Reply #114 on:** April 29, 2016, 09:20:22 AM »

According to Mann et al. (2016) this species grows about 35 mm/year. So that fish in the pic (assuming it was 25 cm long), would be roughly 7 years old.

And it would actually be a teenager!!!! It grows to 80 cm and about 12 kg!!!!

REEFMAN · « **Reply #115 on:** April 29, 2016, 11:58:25 AM »

Pffft 25cm.
It was 63cm long...

18 or so years... thank goodness I put it back

WalkersKiller · « **Reply #116 on:** April 29, 2016, 12:02:12 PM »

Thats an old fish!

John F · « **Reply #117 on:** April 29, 2016, 12:47:09 PM »

Quote from: REEFMAN on April 29, 2016, 11:58:25 AM

Pffft 25cm.
It was 63cm long...

18 or so years... thank goodness I put it back

oops sorry!!! in my defense, that tape must be in inches

That was a great catch!

colin · « **Reply #118 on:** April 29, 2016, 03:30:56 PM »

Thats an old fish!
[/quote] walkerskiller

even older tape

John F · « **Reply #119 on:** May 04, 2016, 12:08:16 PM »

Plastic ingestion by estuarine mullet Mugil cephalus (Mugilidae) in an urban harbour, KwaZulu-Natal, South Africa

* Coastal urban environments have high plastic pollution levels, and hence interactions between plastic debris and marine life are frequent;

* Plastic ingestion by mullet Mugil cephalus in Durban Harbour, KwaZulu-Natal, South Africa is reported;

* Of 70 mullet (13.0–19.5 cm total length), 73% had plastic particles in their guts, with a mean of 3.8 particles per fish (SD 4.7);

* Plastic ingestion showed no relation to digestive tract content or fish length;

* White and clear plastic fibres were ingested most commonly;

* This urban population of M. cephalus had a higher incidence of plastic ingestion than has been reported in studies on fish from other coastal areas or the oceanic environment.

PDF available.

Reference:
Naidoo, T., A.J. Smit & D. Glassom (2016).Plastic ingestion by estuarine mullet Mugil cephalus (Mugilidae) in an urban harbour, KwaZulu-Natal, South Africa. African Journal of Marine Science, 38: 145-149.